(2020) 8:114
Tamburini et al. Herit Sci
https://doi.org/10.1186/s40494-020-00441-9
Open Access
RESEARCH ARTICLE
Exploring the transition from natural
to synthetic dyes in the production
of 19th-century Central Asian ikat textiles
Diego Tamburini1* , Eric Breitung1,2, Chika Mori1,3, Tomoko Kotajima1,4, Matthew L. Clarke1
and Blythe McCarthy1
Abstract
This study focuses on the dye analysis of 26 ikat textiles present in the collection of the Arthur M. Sackler Gallery and
originally collected by Dr. Guido Goldman with the aim to gain additional information about their provenance and
dating. The investigation exploits the full potential of a multi-analytical approach, starting with a non-invasive survey
of all the colors using fiber optic reflectance spectroscopy (FORS), which revealed the presence of indigo and insectbased red dyes. These data were used to select areas from which samples were taken and analyzed by high performance liquid chromatography diode array detector (HPLC–DAD). These results enabled most of the natural sources
of dyes to be fully identified, including American cochineal (Dactylopius coccus), madder (probably Rubia tinctorum),
lac (probably Kerria lacca), larkspur (Delphinum semibarbatum), pagoda tree flower buds (Sophora japonica), grape vine
leaves (Vitis vinifera), indigo and tannins. Complex mixtures of dyes were present in most samples, as a result of both
the ikat making process itself and traditional dyeing practices. Synthetic dyes were identified in 9 of the textiles. Samples were re-analyzed using HPLC–DAD coupled to mass spectrometry (HPLC–DAD-MS). Malachite green (basic green
4, C.I. 42000), fuchsine (basic violet 14, C.I. 42510), rhodamine B (basic violet 10, C.I. 45170) and methyl violet (basic
violet 1, C.I. 42535) were identified, and a few other tentatively identified synthetic dyes (probably orange I, II and IV,
rhodamine 6G, patent blue V and alizarin yellow GG) were detected. As the first synthesis of early synthetic dyes is well
documented, their presence was used to refine the dating of these textiles. The contextualization of the results also
appeared to support the stylistic assumption that more intricate and colorful designs with a higher level of complexity are dated earlier than simpler, larger and more graphic ones. The overall information acquired reveals a dynamic
scenario and an interesting window into the dyers’ experiments and adjustments to the economic and technological
changes of the nineteenth century.
Keywords: Ikat, Central asia, Natural dyes, Early synthetic dyes, Liquid chromatography, Goldman collection
Introduction
Ikat textiles are among the most famous and recognizable fabrics worldwide and they are historically produced in several parts of the world, including Central
and Southeast Asia, some Middle Eastern and African
*Correspondence: TamburiniD@si.edu
1
Department of Conservation and Scientific Research, Freer Gallery of Art
and Arthur M. Sackler Gallery, National Museum of Asian Art, Smithsonian
Institution, 1050 Independence Ave SW, Washington, DC 20560, USA
Full list of author information is available at the end of the article
regions, Central and South America, India and Japan.
The word ikat derives from the Malaysian word mengikat, meaning “to tie”: in fact, the patterns and decorations are obtained by adopting a specific process, in
which bundles of threads are repeatedly bound with a
resist material and dyed, in order to only fix the color in
the areas left exposed. The design is therefore created in
the yarns rather than on the finished cloth, which makes
the process very difficult and time-consuming. The weaving is then carefully carried out after stretching the dyed
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Tamburini et al. Herit Sci
(2020) 8:114
threads on a loom in the correct order. Consequently,
these textiles are patterned with a typical “blurriness” or
feather-like effect, as a result of the color in the dye bath
bleeding under the resist material and of the slight movement of threads caused by the strains imposed by the
weaving process [1].
A significant amount of research has been conducted
to track the origin of the ikat technique and highlight the
cultural importance of the practice, and there is common
consensus that the practice originated independently in
the different continents [1–7]. Nevertheless, tracking the
origin of Central Asian ikats is a complicated task, due
to the scarce archaeological evidence, as well as the lack
of evidence of ikat production throughout the seventeenth century. Moreover, Central Asia is a broad term
referring to a vast geographical region, which has never
corresponded to one political entity and whose historical importance is partially related to it being located at
the heart of the Silk Road [1, 6, 7]. Although silk and
sericulture were introduced from China in very ancient
times, an Indian origin of the ikat-weaving technique
is sometimes hypothesized [6]. Regardless of the ultimate answer to the origin of the ikat tradition, by the
nineteenth century, following the domination period of
the Uzbeks and before falling under the control of the
Russian empire, Central Asia was producing a worldrenowned variety of ikats, and the technique was at its
highest point [1]. Traditionally used as clothing for both
men and women, these textiles acquired a huge role in
the cultural life of the region, as they were intended for
weddings and important events, as markers of status,
as decorative wall-hangings, gifts and ritual objects. In
addition to their functions, they have always retained an
artistic expression in their own right [1, 8]. The motifs
and patterns reflect the Central Asian melting pot of people and cultures. Many motifs are pre-Islamic in origin,
descending from Turkic tribal groups and carry some
mystical value, such as the scorpion (poisonous, symbolic
of warding off evil) and the jug of water (symbol of purity,
especially to Muslims who are expected to wash before
prayer). Most motifs are deeply rooted in Persian iconography and Islamic forms, such as the cypress tree, but
artisans reused them, recycled them, and tweaked them,
sometimes making connections with the original designs
difficult. Rams’ horns motifs, “eye spot” patterns, triangular amulets, arachnids, flowers and pendants reminiscent of jewelry are common Central Asian patterns. The
Islamic mastery of geometrical design is also commonly
showcased [8, 9]. Some of these motifs are present on the
ikats under investigation in this study and are shown in
Fig. 1.
It is not surprising that such exquisite textiles attracted
the attention of collectors. Among them is Dr. Guido
Page 2 of 27
Goldman, who donated 76 ikat textiles from his personal
collection to the Arthur M. Sackler Gallery. In a collector’s note, Guido Goldman wrote “…as I purchased more
ikats I had no well-formed purpose in mind other than
the desire to acquire pieces that moved me. It was color
and design, and to some degree condition, that determined what I bought. I avoided ikats that were chemically dyed, preferring multi-colored ikats with relatively
complex designs, which generally meant those of an
earlier period” [1]. His words reveal his intention to buy
traditionally-made and relatively old ikats, but also hint
towards one of the main issues with these objects, which
is the lack of information on their production date and
provenance. Some ikats have reliable dating and provenance, such as some pieces at the State Hermitage
Museum (St Petersburg, Russia), which were sent as gifts
from Khans to the Russian Tsar [10], or those in the Robert Shaw collection at the Ashmolean Museum (Oxford,
UK), as the exact dates of Shaw’s travels are known [11].
However, the most common scenario is for the pieces
to have come to the collectors through art dealers, and
the original information is inevitably lost. Even when the
acquisition place is recorded, the pieces may still have
been made and worn elsewhere. Dating is even more
problematic and is often based on the stylistic assumption that more complex and colorful designs are dated
earlier than simpler and larger ones. The complexity and
labor is measured in terms of how small the binds are and
how frequently the color changes along a warp length, so
larger and more graphic designs correspond to a simpler
method of production [9].
In Bukhara and Samarkand, which are reported as the
main centers of production in the nineteenth century,
the making of ikats was a standardized process, which
involved several workshops, and is documented by nineteenth century ethnographic literature and photos [1].
The preparation of the warp silk threads was done using
a wooden wheel as measuring unit for the thread length
(generally 202.5 m). The number of threads in a warp was
commonly 48, referred to as a livit. After a gentle boiling
with potash, the whitened warps were stretched, dried
and sent to the abr-bandi (ikat-binding) workshop, in
which a special wooden board was used. The board contained between 40 and 60 holes evenly spaced and each
livit was passed through one hole and knotted on one
hand of the board. Then, two wooden beams were placed
at the exact distance representing the patterning frame,
and the entire length was wound around the two beams
using the pierced wooden board to keep all the livits in
place. The outlines of the pattern were marked with charcoal and waterproof (greased) cotton strings were tied
around small bundles of threads to prevent these areas
from coming into contact with the first dyestuff. After
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(2020) 8:114
Page 3 of 27
Fig. 1 Motifs present on some of the ikats investigated from the Arthur M. Sackler Gallery collection, Smithsonian Institution, Washington, DC: gifts
of Guido Goldman. Top: left—crescent and flowers (S2004.66); middle—amulets (S2004.91); right—tambourines and S-curved horns (S2004.84).
Bottom: left—rams’ horns (S2004.78); middle—cypress trees (S2004.85); right—heart-shaped asyk or shagai, probably representing the ankle bones
of a sheep or goat (S2004.92)
careful removal from the frame, the threads were sent to
the dye house. Muslim dyers specialized in hot mordant
dyeing with red and yellow vegetable dyes, and Jewish
dyers specialized in indigo cold vat dyeing. Therefore, the
threads were often dyed in at least two different places.
The most prestigious and expensive type of fabric was the
seven-color ikat or haftrang, obtained by immersing the
warp in three subsequent dye baths: first yellow, then red,
and finally dark blue. The last, over-dyed on yellow or red
areas, gave green and purple shades. Between each dye
bath, the threads had to return to the abr-bandi workshop and another set of binds was applied. Finally, the
dyed threads were sent to the weaving workshop, where
they were stretched on simple treadle looms and a plain
weave fabric was generally obtained using non-patterned
cotton wefts [1, 9, 12].
Scientific analysis, in particular dye identification, provides useful information when it comes to addressing
provenance and dating questions. Specific types of natural dyes are used in certain geographical areas [13–15]
and are reported to be used before or after a certain date
[16]. In addition, synthetic dyes were created in the second half of the nineteenth century [17], and their first
synthesis is documented with precise dates [18, 19].
Although Goldman explicitly avoided ikats that did not
look naturally dyed, one of the main focuses of this study
Tamburini et al. Herit Sci
(2020) 8:114
was to check on the presence of synthetic dyes to use
them as dating tool and establish the terminus post quem
production dates.
Dye analysis on Central Asian ikats is very scarce [20].
Based on previously published research, it appears that
the following sources of dyes were used: madder (Rubia
tinctorum) and cochineal, American cochineal (Dactylopius coccus) and possibly a local species, for red and purple, larkspur (Delphinum semibarbatum) and pagoda tree
flower buds (Sophora japonica) for yellow, and indigo
for blue [1, 20]. Dyeing recipes are also reported in nineteenth century ethnographic literature and these include,
in addition to the above-mentioned dyes, the use of sandalwood (Pterocarpus santalinus) and sappanwood (Caesalpinia sappan) for red and purple, as well as the use of
pomegranate skin, mallow flower, rhubarb, pistachio galls
and mulberry leaves as sources of tannins [1].
Analytical methods for the identification of dyes have
been developed in the past decades [21]. It has been
shown that high pressure liquid chromatography (HPLC)
techniques have the highest potential in terms of the level
of detail and accuracy that can be obtained [22]. The molecules extracted from the fibers are chromatographically
separated and identified singularly, thus enabling complex mixtures to be characterized. Dye sources can often
be identified down to the species of the plant or animal
from which they were produced [23–27]. The molecular
detection and identification is usually possible by using
a diode array detector (DAD), as the typical UV–Vis
absorption spectra and retention times produce sufficient information to identify the most common sources
of natural dyes [28–30]. However, mass spectrometry
(MS) detectors have affirmed their advantages, especially
in terms of identification of degradation products and
relevant non-colored molecules, so that HPLC–DADMS is largely applied to dye identification [31, 32]. More
recently, the application of high resolution mass spectrometry (HRMS) and tandem mass spectrometry (MS/
MS) has opened new possibilities in terms of elucidating
structures, distinguishing between isomers and identifying new sources of dyes [33–43]. In particular, these
detectors are especially useful when complex isomeric
mixtures are present, as they provide an additional level
of separation that can sometimes not be achieved by
chromatography [44].
Although the amount of sample required nowadays
for HPLC analysis is minimal (2–3 mm of a thread),
sampling is not always possible when dealing with precious and fragile textiles and non-invasive approaches
are highly desirable. Non-destructive surface techniques,
such as UV–Vis reflectance and luminescence spectroscopies, have been applied to identify a limited number of
colorants [45–51]. Similarly, multispectral imaging (MSI)
Page 4 of 27
has been recently introduced as a useful tool for studying the distribution of the dyes on large surfaces with the
possibility to identify selected dyes [52–55]. Nonetheless, non-invasive investigations produce limited information, especially when it comes to yellow dyes, most
of which are hardly distinguishable from each other in
terms of their fluorescence and reflectance spectra, or
dye mixtures. As a result, recent studies have focused on
the delineation of protocols aimed at identifying dyes in
textiles using a combination of non-invasive techniques
(microscopy, FORS and MSI), whose results can guide
a selective sampling of areas of particular interest to be
analyzed by HPLC techniques [40, 54, 56–58].
In this framework, our study focused on the scientific
investigation of 26 ikat textiles with the aim to identify
the dyes present, using FORS to screen all the colors and
select the areas to be sampled and analyzed by HPLC–
DAD. A further selection of samples was then made
based on the suspected presence of synthetic dyes, and
these samples were finally analyzed by HPLC–DAD-MS.
Materials and methods
Objects and samples
The 26 ikats under investigation were originally collected
by Dr. Guido Goldman and donated to the Arthur M.
Sackler Gallery between 2004 and 2007. They include 19
wall hangings, 3 loom length textiles (1 complete and 2
sections) and 4 woman’s robes (munisak). They are all
warp-faced plain weave ikats with cotton wefts and silk
warps, with the exception of 4 silk velvets (S2004.78,
S2004.95, S2004.96 and 2007.30). They are all attributed
to the nineteenth century, supposedly spanning from
the beginning to the end of the century, mostly based
on stylistic interpretation. For most, the geographical
provenance is Uzbekistan. In some cases, they are more
precisely related to Bukhara, Samarkand or the Ferghana
valley, whereas in other cases a general Central Asian
provenance is ascribed. The textile S2004.85 is considered Iranian, based on the typical cypress tree design, but
it is not certain if it was made in Iran or in Central Asia
by Iranian craftsman.
98 samples (ca. 1 cm of a thread corresponding to
ca. 0.5 mg) were taken as representative of most colors
exhibited. For the ikats composed of multiple panels,
samples were not always taken from the same panel, as
priority was given to sampling from already-damaged,
easily accessible areas. Although it is generally assumed
that the panels of the same ikat are from the same loom
and have therefore been dyed in the same way, it is
also known that different panels were sometimes sewn
together, borders were added and additions were made
in order to change the dimension of an ikat. As we were
not able to sample all the panels of each ikat, the fact that
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different dyes might be present in different panels from
the same ikat should be taken into consideration when
interpreting the results. The number of panels and information about whether the samples were from the same
panel or not are reported in Table 1.
FORS
FORS measurements were carried out for all colored
areas. Spectra were acquired using a Cary 50 ultraviolet–
visible spectrophotometer with a six-around-one fiber
optic reflectance probe, whose instrumental details are
described in [59]. Data were acquired in the range 190–
950 nm in reflectance mode at a scan rate 120 nm/min,
with 1 nm data interval and 0.5 s average time. A baseline
correction was applied using a white diffuse reflectance
standard (Spectralon® Calibrated Reflectance Standard #SRS 99-010, Labsphere) Smoothing was performed
using the Cary 50 software.
HPLC–DAD
All 98 samples were analyzed by HPLC–DAD. Dye
extraction was performed by adding 200 µL of a mixture of oxalic acid (0.2 M), acetone, methanol and water
(1:30:30:40 v:v:v:v) to the samples and then keeping
them for 30 min at 60 °C. The solution was then transferred to a 2 mL vial and dried under vacuum over 2–4 h
at room temperature. The residue was reconstituted in
40 µL of a mixture of methanol and water (1:1 v:v). The
vial was capped and centrifuged for 10–20 s and 20 µL of
the extracts were introduced to the HPLC system via an
auto-sampler.
The HPLC system was an Agilent 1100 equipped with
a binary pump and a diode array (DAD) detector. Separation was achieved using a Phenomenex Kinetex C18
reversed phase column (2.1 mm × 100 mm, 2.6 μm particle size) and a gradient of eluent A (1% formic acid,
5% methanol, 94% water) and eluent B (1% formic acid
in methanol) programmed as follows: initial conditions
0–0.5 min 15% B, 0.5–25 min 15–85% B, 25–27 min 85%
B, 27–29 min 85–15% B. The flow rate was 0.25 mL/min.
Integration of chromatographic peak areas was performed at different wavelengths (optimal wavelengths are
350 nm for yellow molecules, 450 nm for red molecules,
550 nm for purple molecules and 600 nm for blue molecules) using the automatic integration function of the
Chemstation (Agilent) software, in order to obtain broad
estimations (percentages) of the extract content, following published methods [28]. In the case of the published
data, the relative standard deviation related to this type of
operation is less than 10% [28]. The percentages reported
in Table 1 derive from integrations performed at 254 nm
of all the chromatographic areas corresponding to all
the molecules identified in a sample. The percentages
Page 5 of 27
obtained from the molecules related to the same dye
source were then summed to obtain the reported values.
254 nm was chosen to have some internal consistency, as
the detection of most relevant molecules was possible at
this wavelength [20], although it is not optimal in terms
of the absolute percentage values obtained, especially for
blue molecules. The percentages are useful for internal
comparisons among samples and should not be considered actual concentrations.
HPLC–DAD‑MS
A selection of 22 samples suspected to contain synthetic
dyes was re-analyzed using HPLC–DAD-MS. The extraction method used is described in [27] and briefly consisted of a single extraction using 200 µL of a solution of
pyridine/water/1.0 M oxalic acid in water (45:45:10 v:v:v)
at 100 °C for 15 min, followed by cooling to room temperature, evaporation to dryness and re-dissolution of
the residue in 50 µL of methanol/water (1:1). After final
centrifugation at 12,000 rpm, 30 µL of the supernatant
was transferred to an insert in an auto-injector vial and
20 µL was injected onto the HPLC column. This extraction method, compared to the one used for HPLC–DAD,
was optimized to provide good recovery for a very broad
range of categories of natural and synthetic dyes [27, 60].
A Shimadzu LCMS-2020 instrument was used, consisting of an automatic injector, a gradient pump, diode
array detector (DAD), electrospray ionization (ESI)
interface and a quadrupole (Q) analyzer. Operation of
the system and data analysis were done using the LabSolutions software (ver. 5.1.1), and detection was carried
out in both negative and positive ionization modes. The
separation of the dye components was carried out using
a Phenomenex Luna C18 reversed phase column (2 mm
dia. × 150 mm long; 3-μm particle size), operated at a
flow rate of 0.18 mL/min. Elution was achieved with a linear gradient of water with 0.1% formic acid and acetonitrile with 0.1% formic acid from 18 to 95% acetonitrile.
The DAD detector scanned in the range 190–800 nm.
The ESI experimental conditions were: interface voltage
4.5 kV, interface temperature 350 °C, desolvation line
(DL) temperature 250 °C, nebulizing gas flow 1.5 L/min,
drying gas flow 15 L/min, heat block temperature 200 °C.
MS data were acquired in the range 100–1000 m/z at
scan speed 1875 u/sec and with Q-array RF voltage 60 V.
For both HPLC–DAD and HPLC–DAD-MS analysis,
dye components were associated with natural and synthetic dye sources using data measured from reference
materials (retention times, UV–Vis spectra and mass
measurements) made available by the Getty Conservation Institute (Los Angeles, USA) [61], as well as from the
published literature [14, 23, 24, 27, 37, 38, 40, 44, 62–64].
Description
Color
FORS
HPLC–DAD*/HPLC–DAD-MS
S2004.66**
Wall hanging
1850–1875
Uzbekistan, probably Samarkand
6 panels, warp-faced plain weave; silk, cotton
H × W: 211 × 175 cm
Blue
Indigo
Indigo (70), pagoda tree flower buds (30)
Green
Indigo and unidentified yellow
S2004.68**
Wall hanging
Mid-nineteenth century
Uzbekistan, probably Samarkand
4 panels, warp-faced plain weave; silk, cotton
H × W: 229 × 102 cm
S2004.72***
Wall hanging
1850–1875
Uzbekistan, probably Bukhara
2 panels, warp-faced plain weave; silk, cotton
H × W: 130 × 72 cm
Purple
Indigo and insect red
Red
Insect red
(2020) 8:114
Image
Tamburini et al. Herit Sci
Table 1 Description of the ikats under investigation and summary of the results obtained by dye analysis. The dates reported are those attribute based
on stylistic interpretation, expect for the ikats in which synthetic dyes were found (terminus post quem production dates are reported in bold for these textiles).
For HPLC-DAD analysis, the values between paranthesis are percentages resulting from the intergration of the chromatographic areas (254 nm) of all peaks
(dye molecules) attributed to the molecular components of the dye source considered. All dye molecules identified for each dye source are discussed in detail
in the corresponding sections. The results reported in italic were obtained by additional HPLC-DAD-MS analysis
Cochineal (80), larkspur (15), lac (2), madder (1),
indigo (1)
Pink
Insect red
Yellow
Unidentified
Larkspur (85), pagoda tree flower bud (10), madder
(4), indigo (1)
Blue
Indigo
indigo (75), madder (5), quercetin (20)
Green
Indigo and unidentified yellow
larkspur (85), indigo (12), madder (3)
Purple
Indigo and insect red
Red
Insect red
Cochineal (90), madder (7), tannins (1), lac (2)
Yellow
Unidentified
larkspur (95), madder (4), indigo (1)
Blue
Indigo
Indigo (35), larkspur (55), cochineal (3), madder (7)
Green
Indigo and unidentified yellow
Indigo (65), possibly synthetics (35)/indigo, larkspur,
traces of madder
Purple
Indigo and insect red
Cochineal (75), tannins (5), madder (15), indigo (5)
Red
Insect red
Cochineal (70), tannins (5), madder (22), indigo (3)
Yellow
Unidentified
Larkspur (80), madder (5), cochineal (5), tannins (10)
Page 6 of 27
Image
Color
FORS
HPLC–DAD*/HPLC–DAD-MS
S2004.75***
Wall hanging
Mid-nineteenth century
Central Asia
4 panels, warp-faced plain weave; silk, cotton
H × W (overall): 123 × 114 cm
Blue (dark)
Indigo
Indigo (35), larkspur (60), cochineal (2), madder (2)
Blue (light)
Indigo
Indigo (50), cochineal (25), tannins (25)
Green
Indigo and unidentified yellow
Indigo (13), larkspur (85), madder (2)
Purple
Indigo and insect red
Cochineal (80), tannins (2), madder (8), larkspur (5),
indigo (5)
Red
Insect red
Cochineal (95), tannin (2), madder (3)
Yellow
Unidentified
Larkspur (85), cochineal (10), madder (3), indigo (2)
Indigo
Indigo (45), larkspur (45), cochineal (5), madder (5)
Indigo
Indigo (65), cochineal (25), madder (10)
Indigo and unidentified yellow
Indigo (15), cochineal (25), madder (10), larkspur (50)
S2004.76***
Blue (dark)
Wall hanging
Mid-nineteenth century; Uzbekistan, Bukhara
6 panels, warp-faced plain weave; silk warps, cotton Blue (light)
wefts
Green
H × W (overall): 175 × 159 cm
Purple
S2004.78
Complete loom length textile
Nineteenth century
Central Asia
1 panel, silk velvet
H × W: 678 × 41 cm
(2020) 8:114
Description
Tamburini et al. Herit Sci
Table 1 (continued)
Indigo and insect red
Red
Insect red
Cochineal (80), madder (10), tannins (10)
Yellow
Unidentified
larkspur (90), madder (8), indigo (2)
Blue
Indigo
Indigo (45), cochineal (25), tannins (35)
Green
Indigo and unidentified yellow
Indigo (15), larkspur (75), cochineal (10)
Purple
Indigo and unidentified red
cochineal (90), tannins (5), indigo (5)
Red
Unidentified
Cochineal (95), tannins (3), madder (2)
Yellow
Unidentified
Larkspur (95), cochineal (2), probably synthetic yellow (3)/larkspur, pagoda tree flower buds, cochineal,
alizarin
Orange
Unidentified
probably synthetic orange (95), indigo (5)/cochineal,
grape vine leaves (Vitis vinifera)
Page 7 of 27
Image
Color
FORS
HPLC–DAD*/HPLC–DAD-MS
S2004.79
Section of loom length;
After 1877
Central Asia
1 panel; warp-faced plain weave; silk warps, cotton
wefts
H × W: 198 × 28 cm
Blue
Indigo
Indigo (90), synthetic (10)/indigo, synthetic orange
(probably an azo dye similar to orange IV)
Green
Synthetic
Synthetic (100)/larkspur, malachite green, traces of
cochineal
Purple
Indigo and unidentified red
Cochineal (98), indigo (2)
Red
Insect red
Cochineal (95), probably synthetic (5)/cochineal,
tannins
Yellow
Unidentified
Blue
Indigo
S2004.80**
Wall hanging
1850–1875
Uzbekistan, Samarkand or Ferghana Valley
5.5 panels, warp-faced plain weave; silk warps,
cotton wefts
H × W: 221 × 150 cm
Indigo (100)
Blue-green
Indigo and unidentified yellow
indigo (22), larkspur (75), madder (3)
Purple
Indigo and insect red
cochineal (90), tannins (7), indigo (3)
Red
Insect red
Cochineal (96), tannins (2), madder (1), indigo
(1)/cochineal, tannins
Yellow
Unidentified
larkspur (85), pagoda tree flower buds (10), indigo
(5)/larkspur, pagoda tree flower buds, cochineal
Indigo
indigo (50), cochineal (25), tannins (25)
Indigo and unidentified yellow
Larkspur (90), indigo (3), madder (2), synthetic
(5)/larkspur, indigo, rhodamine B
Insect red
cochineal (90), tannins (5), synthetic (5)/cochineal,
tannins, rhodamine B
S2004.81**
Blue
Wall hanging
After 1887
Green
Central Asia, Ferghana Valley
6 panels, warp-faced plain weave; silk warps, cotton
wefts
Red
H × W: 203 × 171 cm
(2020) 8:114
Description
Tamburini et al. Herit Sci
Table 1 (continued)
Page 8 of 27
Image
Description
Color
S2004.83**
Wall hanging
1800–1850
Uzbekistan, Bukhara
6 panels in center, warp-faced plain weave; silk
warps, cotton wefts
H × W: 246 × 211 cm
S2004.84***
Wall hanging
Probably after 1876
Uzbekistan, Bukhara
3.5 panels, warp-faced plain weave; silk warps,
cotton wefts
H × W: 231 × 1150 cm
HPLC–DAD*/HPLC–DAD-MS
Synthetic
Malachite green, synthetic blue (probably patent
blue V) and synthetic yellow (probably alizarin
yellow)
Mixture of natural and synthetic (?)
Insect red
Cochineal (55), lac (20), madder (12), tannins (3),
malachite green (10)
(2020) 8:114
S2004.82**
Blue-green
Wall hanging
Probably after 1888
Central Asia
Purple
3 panels, warp-faced plain weave; silk warps, cotton
Red
wefts
H × W: 178 × 110.9 cm
Yellow
FORS
Tamburini et al. Herit Sci
Table 1 (continued)
Unidentified
Blue
Indigo
Green
Indigo and unidentified yellow
Cochineal (15), larkspur (75), madder (5), indigo (5)
Purple
Indigo and unidentified red
Cochineal (15), tannins (20), madder (5), indigo (60)
Red
Insect red
Cochineal (65), madder (20), tannins (12), probably
synthetic (3)/cochineal, madder, tannins
Yellow
Unidentified
larkspur (95), madder (3), indigo (2)
Blue
Indigo and synthetic (?)
Purple/green
Indigo, insect red and unidentified
Cochineal (5), indigo (5), larkspur (85), probably
synthetic (5)/cochineal, indigo, larkspur, not fully
identified compounds (possibly orange I, orange II and
other azo dyes)
Red
Insect red
Cochineal (15), synthetic (85)/cochineal, fuchsine
Yellow
Unidentified
Larkspur (94), cochineal (2), indigo (2), synthetic (2)
Page 9 of 27
Image
Description
HPLC–DAD*/HPLC–DAD-MS
Indigo (60), madder (35), synthetic (5)
Blue (dark)
Indigo
Blue (light)
Synthetic
Green
Synthetic
Larkspur (90), synthetic green (10)/larkspur, malachite
green, cochineal, madder
Red
Unidentified
cochineal (68), tannins (30), madder (2)/cochineal,
tannins, traces of malachite green
Yellow
Unidentified
S2004.88***
Red (dark)
Wall hanging
Red (light)
1850–1875
Uzbekistan, possibly Samarkand
Yellow 1
5 panels, warp-faced plain weave; silk warps, cotton
wefts
H × W: 204 × 140 cm
S2004.89
Section of loom length
After 1877
Central Asia
1 panel, warp-faced plain weave; silk warps, cotton
wefts
H × W: 234 × 33 cm
FORS
Insect red
(2020) 8:114
S2004.85
Wall hanging
After 1877
Iran
Single loom width, warp-faced plain weave; silk
warps, cotton wefts
H × W: 180 × 109 cm
Color
Tamburini et al. Herit Sci
Table 1 (continued)
Cochineal (85), lac (2), madder (3), larkspur (10)
Insect red
Unidentified
Larkspur (98), madder (2)
Blue (dark)
Synthetic
Blue (light)
Synthetic
Blue weft
Indigo
Indigo (100)
Purple
Synthetic
Larkspur (15), synthetic violet (85)/larkspur, methyl
violet
Green
Synthetic
larkspur (40), indigo (10), synthetic green (50)/larkspur, malachite green, indigo
Red (light)
Synthetic
Red (dark)
Synthetic
Cochineal (30), synthetic (70—probably methyl
violet)
Yellow
Unidentified
Larkspur (97), indigo (3)
Page 10 of 27
Tamburini et al. Herit Sci
Table 1 (continued)
Image
Color
FORS
S2004.90***
Wall hanging
ca. 1900
Central Asia
4 panels, warp-faced plain weave; silk warps, cotton
wefts
H × W: 203 × 142 cm
Blue
Indigo
Green
Indigo and synthetic
S2004.91**
Wall hanging
1800–1850
Uzbekistan, Bukhara
3 panels, warp-faced plain weave; silk warps, cotton
wefts
H × W: 169 × 86 cm
S2004.92***
1850–1875
Wall hanging
Central Asia, Ferghana Valley
5.5 panels, warp-faced plain weave; silk warps,
cotton wefts
H × W: 211 × 144 cm
HPLC–DAD*/HPLC–DAD-MS
Purple
Indigo and unidentified
Indigo (35), cochineal (40), tannins (25)
Red
Unidentified
Cochineal (85), tannins (12), madder (3)
Yellow
Unidentified
Larkspur (85), pagoda tree flower buds (8), cochineal
(5), madder (2)
Indigo (35), cochineal (30), tannins (15), madder (20)
Blue 1
Indigo
Green 1
Indigo and unidentified
Purple 1
Indigo and unidentified
Red 1
Insect red
Cochineal (70), madder (30)
Yellow 1
Unidentified
Larkspur (70), cochineal (10), madder (20)
Green
Indigo and unidentified
Indigo (60), larkspur (25), pagoda tree flower buds
(10), madder (5)
Red
Insect red
Cochineal (85), madder (2), tannins (13)
Yellow
Unidentified
Larkspur (55), madder (15), pagoda tree flower buds
(30)
(2020) 8:114
Description
Page 11 of 27
Tamburini et al. Herit Sci
Table 1 (continued)
Image
Color
FORS
HPLC–DAD*/HPLC–DAD-MS
Blue
Indigo
Indigo (60), cochineal (20), larkspur (20)
Larkspur (85), indigo (8), cochineal (6), madder (1)
S2004.96***
Woman’s robe (munisak)
1850–1875
Central Asia
Silk velvet
H × W: 132 × 160 cm
S2005.13**
Woman’s robe (munisak); late nineteenth century
Central Asia; warp-faced plain weave; silk warps,
cotton wefts
H × W: 135 × 165 cm
Green
Indigo and unidentified
Purple
Indigo and unidentified
Purple
Indigo and insect red
Red
Unidentified
Red
Unidentified
Yellow
Unidentified
Larkspur (98), madder (1), indigo (1)
Blue
Indigo
Indigo (65), probably synthetic (35)/indigo, traces of
larkspur and cochineal
Indigo (12) larkspur (85), madder (3)
Cochineal (80), tannins (17), madder (1), indigo (2)
Green
Indigo and unidentified
Purple
Indigo and insect red
Red
Insect red
Cochineal (85), tannins (13), madder (2)/cochineal,
larkspur, tannins
Yellow
Unidentified
Larkspur (100)
Blue
Indigo
Green
Indigo and unidentified
Purple
Indigo and unidentified
Red
Unidentified
Yellow
Unidentified
(2020) 8:114
Description
S2004.95***
Woman’s robe (munisak)
1850–1875
Central Asia
Silk velvet
H × W: 165 × 122 cm
Cochineal (38), madder (55), tannins (2), indigo (5)
Larkspur (72), madder (25), indigo (3)
Page 12 of 27
Image
Color
FORS
HPLC–DAD*/HPLC–DAD-MS
S2005.17**
Woman’s robe (munisak); nineteenth century
Central Asia; warp-faced plain weave; silk warps,
cotton wefts
H × W: 129.5 × 161 cm
Blue
Indigo
Indigo (100)
Green
Indigo and unidentified
Larkspur (95), indigo (4), madder (1)
Purple (dark)
Indigo and unidentified
cochineal (90), tannins (6), indigo (4)
Purple (reddish) Indigo and insect red
Red
Insect red
Yellow
Unidentified
Brown
S2006.20
Wall hanging
1840–1875
Uzbekistan, probably Samarkand
2 full panels and 2 half panels center; cut panels
in borders; warp-faced plain weave; silk warps,
cotton wefts
H × W: 206.4 × 148 cm
S2006.21***
Wall hanging
Mid-nineteenth century
Uzbekistan, Bukhara or Samarkand; 6 panels, warpfaced plain weave; silk warps, cotton wefts
H × W: 226.1 × 168.3 cm
(2020) 8:114
Description
Tamburini et al. Herit Sci
Table 1 (continued)
Cochineal (50), tannins (3), larkspur (45), madder (1),
indigo (1)
Blue (border)
Indigo
Blue (center)
Indigo
Green (border)
Indigo and unidentified
Green (center)
Indigo and unidentified
Purple
Indigo and insect red
Indigo (100)
Red (border)
Insect red
Cochineal (67), lac (13), madder (20)
Red (center)
Insect red
cochineal (67), tannins (7), lac (25)
larkspur (100)
Yellow (border)
Unidentified
Yellow (center)
Unidentified
Blue
Indigo
Indigo (80), madder (20)
Green
Indigo and unidentified
Larkspur (95), indigo (4), madder (1)
Purple
Indigo and unidentified
Red (light)
Insect red
Red (dark)
Insect red
Yellow
Unidentified
Cochineal (70), madder (10), lac (3), tannins (12),
indigo (2)
Page 13 of 27
Tamburini et al. Herit Sci
Table 1 (continued)
Description
Color
FORS
HPLC–DAD*/HPLC–DAD-MS
2007.30**
Wall hanging
After 1892
Uzbekistan, probably Bukhara
3.5 panels, warp-faced plain weave; silk warps, cotton wefts; silk velvet
H × W: 180.3 × 116.8 cm
Green
Synthetic
Larkspur, malachite green, synthetic blue (probably
patent blue V) and synthetic yellow (probably
alizarin yellow)
Purple
Synthetic (?)
Larkspur, malachite green, synthetic blue (probably
patent blue V), fuchsine, rhodamine B/rhodamine
6G
Red
Synthetic (?)
fuchsine (80), rhodamine B-rhodamine 6G (20)
Yellow
Unidentified
larkspur (75), rhodamine B-rhodamine 6G (25)
Indigo and unidentified
Indigo (20), cochineal (10), probably synthetic
(70)/indigo, cochineal, pagoda tree flower buds,
rhodamine B
2007.35**
Blue
Wall hanging
After 1887
Uzbekistan
4 panels, warp-faced plain weave; silk warps, cotton Green
wefts
Purple
H × W: 201.3 × 144.8 cm
(2020) 8:114
Image
Indigo and unidentified
Indigo and unidentified
Cochineal (55), indigo (45)/indigo, cochineal, pagoda
tree flower buds, rhodamine B
Red
Insect red
Cochineal (95), madder (3), indigo (2)
Yellow
Unidentified
Larkspur (100)/cochineal, pagoda tree flower buds
The dates reported are those attributed based on stylistic interpretation, except for the ikats in which synthetic dyes were found (terminus post quem production dates are reported in bold for these textiles). For HPLC–
DAD analysis, the values between parenthesis are percentages resulting from the integration of the chromatographic areas (254 nm) of all peaks (dye molecules) attributed to the molecular components of the dye
source considered. All dye molecules identified for each dye source are discussed in detail in the corresponding sections. The results reported in italic were obtained by additional HPLC–DAD-MS analysis
*
Percentage values are intended as broad estimations of the extract content for internal comparison, as they do not necessarily correspond to dye concentrations in the threads. In the case of indigo-containing samples,
254 nm is not the best wavelength to detect indigoids, but this wavelength was kept to maintain internal comparability. However, as a result, the absolute values of the indigo percentage are underestimated
**
***
Samples were taken from different panels
Samples were taken from the same panel
Page 14 of 27
Tamburini et al. Herit Sci
(2020) 8:114
Page 15 of 27
Results
The analyses performed led to the identification of all
sources of natural dyes and most sources of synthetic
dyes used to obtain the colors of the ikat textiles under
investigation. The results are summarized in Table 1 and
the implications of the findings are discussed in the Discussion section.
Natural red dyes
The reflectance spectra of most red areas exhibited two
small absorption maxima centered at ca. 525 and 565 nm
(Fig. 2a), thus showing the characteristic profile of insectderived red dyes [49]. Although FORS is able to distinguish between plant-derived (the two absorption maxima
are at ca. 510 and 540 nm) and insect-derived red dyes,
differentiating between the various insect-derived red
dyes, in particular kermes, cochineal and lac, is not possible based solely on their reflectance/absorbance features
in the UV–Vis range [47].
70
The application of HPLC revealed a much more complex picture. The main dye was cochineal in all cases, but
only in the case of S2004.79 it was found to be the only
red dye present, whereas mixtures of cochineal and madder, cochineal and lac, or even cochineal, lac and madder
were detected in all the other red areas (Table 1).
Cochineal is a general term used to refer to various
insect species, among which American cochineal (Dactylopius coccus), Armenian cochineal or Armenian carmine
scale insect (Porphyrophora hamelii) and Polish cochineal or Polish carmine scale insect (Porphyrophora polonica) are historically the most commonly used to produce
this red dye. Differentiating the three species is reported
to be possible based on the calculation of the chromatographic areas of the various anthraquinones composing
the coloring mixture [24, 65]. Specific molecular markers
have also been recently identified [14, 37]. In our case,
the identification of cochineal was based on the detection of carminic acid (λmax = 280, 495 nm; [M–H]− at m/z
red S2004.66
a
80
70
Reflectance %
60
Reflectance %
yellow S2004.66
b
50
40
565
30
525
60
50
40
30
20
20
10
10
400
80
500
c
0
400
600
700
800
900
Wavelength (nm)
blue S2004.66
80
60
800
900
green S2004.66
purple S2004.66
d
60
720
Reflectance %
Reflectance %
600
700
Wavelength (nm)
70
70
50
40
30
50
40
30
20
20
10
10
0
400
500
500
600
700
Wavelength (nm)
800
900
0
400
565
525
500
600
700
Wavelength (nm)
800
900
Fig. 2 Reflectance spectra acquired by FORS, showing an insect-red dye (a), an unidentified yellow (b), indigo (c), mixtures of indigo and insect-red
dye, and indigo and unidentified yellow (d)
Tamburini et al. Herit Sci
(2020) 8:114
Page 16 of 27
kermesic acid
flavokermesic acid
dc9
dcVII
15.0
17.5
Retention time (min)
20.0
22.5
25.0
27.5
isorhamnetin-3-O-glycoside
Relative abundance
100
12.5
kaempferol-3-O-glycoside
10.0
kaempferol-3-O-rutinoside
quercetin-3-O-glycoside
7.5
quercetin-3-O-rutinoside (rutin)
5.0
dcIV
dc5
a
dc2
dcII
Relative abundance
100
0
to the general values reported for American cochineal
[24, 65], and this was also confirmed by the presence of
specific molecular markers, such as the so-called dc2
(C-glycoside dicarboxylic acid derivative of kermesic
acid; [M–H]− at m/z 521), dc5 (dehydrocarminic acid;
[M-H]− at m/z 489) and dc9 (carminic acid-2′-(4hydroxybenzoate) or carminic acid-2′-salicylate; [M-H]−
at m/z 611) (Fig. 3a) [14]. However, in a few cases the
composition and distribution of the minor components
did not match with any of the three common sources of
carminic acid
491) present as the main component in all the red samples. In most cases, a series of minor components were
detected, which corresponded to the typical compounds
present in cochineal and referred to as dcII (λmax = 290,
440 nm; [M–H]− at m/z 475), dcIV (λmax = 280, 495 nm;
[M-H]− at m/z 491), dcVII (λmax = 280, 495 nm; [M–H]−
at m/z 491), kermesic acid (λmax = 275, 490 nm; [M–H]−
at m/z 329) and flavokermesic acid (λmax = 290, 435 nm;
[M–H]− at m/z 313) (Fig. 3a). The distribution of these
compounds and their percentage areas corresponded
b
0
7.5
10.0
12.5
15.0
17.5
Retention time (min)
20.0
22.5
pseudoindirubin
mAU
5.0
4.0
25.0
27.5
c
indigotin
indirubin
5.0
3.0
5.0
10.0
15.0
20.0
25.0
Retention time (min)
30.0
35.0
40.0
Fig. 3 Chromatographic profiles obtained by HPLC–DAD-MS analysis of (a) a red sample from ikat S2004.96, showing the extract ion
chromatograms for the molecular components of cochineal; (b) a yellow sample from ikat S2004.78, showing the extract ion chromatograms
for the molecular components of a mixture of larkspur and pagoda tree flower buds; (c) a blue sample from ikat S2004.96, showing the UV–Vis
chromatogram extracted at 600 nm with the molecular components of indigo
Tamburini et al. Herit Sci
(2020) 8:114
cochineal. This result is in agreement with some previous
analyses on Central Asian ikats, in which both American
cochineal and a local source of cochineal were proposed
[20]. Nevertheless, it has to be underlined that the use of
chromatographic areas of minor components may not be
precise when it comes to aged historical samples and the
composition of the extracts may not be representative of
the actual composition of the dyes on the threads, as the
extraction procedure may be affected by several unpredictable factors. For these reasons, although American
cochineal is likely to be the main source of red dye in
most these textiles, as expected after the sixteenth century, we decided to refer to it with the general term cochineal (carminic acid based dye).
Lac dye was identified in 6 textiles (S2004.66, S2004.68,
S2004.82, S2004.88, S2006.20 and S2006.21), based on the
detection of laccaic acid A (λmax = 285, 495 nm; [M–H]−
at m/z 536) and laccaic acid B ((λmax = 285, 495 nm;
[M–H]− at m/z 495). Although Kerria lacca is the most
common source of lac dye and most likely the one used
for these textiles, other insects produce a red dye with
very similar composition, e.g. the Paratachardina genus
[25]. Therefore, also in this case, we decided to generally refer to this colorant as lac dye. Lac dye was present
as a minor component (ca. 2% of the chromatographic
areas of all red components) in most cases, except for
S2004.82 and S2006.20, in which it accounted for ca. 20%
of the chromatographic areas of all red components. In
these two samples, laccaic acid C (λmax = 285, 495 nm;
[M–H]− at m/z 538) and laccaic acid E (λmax = 285,
495 nm; [M–H]− at m/z 494) were also detected. These
are reported as minor components of lac dye [25, 40],
and reasonably fell below the detection limit of the technique for all the other samples containing lac dye in very
low concentration.
Madder was identified in most red areas of the textiles
under investigation (Table 1), based on the presence of
alizarin (λmax = 255, 435 nm; [M–H]− at m/z 239), purpurin (λmax = 265, 485 nm; [M–H]− at m/z 255), munjistin
(λmax = 300, 430 nm; [M–H]− at m/z 283) and rubiadin
(λmax = 280, 420 nm; [M–H]− at m/z 253). Similar to
lac dye, madder was present as a minor component in
some cases (ca. 1–4% of the chromatographic areas of
all red components). However, in the red areas of textiles S2004.68, S2004.72, S2004.76, S2004.82, S2004.83,
S2004.91, S2005.13, S2006.20, S2006.21 madder compounds accounted for ca. 5–30% of the chromatographic
areas of all red components. Also in the case of madder,
several plant species of the Rubiaceae family are known
to produce this red dye. Among them, Rubia tinctorum,
R. cordifolia, R. akane and R. peregrina are the most
common and the most studied, and methods to distinguish them based on their chemical compositions have
Page 17 of 27
been proposed [23, 40]. All the samples containing madder showed a relatively higher amount of alizarin compared to purpurin, except for S2004.91 and S2006.21 in
which alizarin and purpurin were present with comparable amounts. Therefore, it appears that the most likely
source of madder dye for the majority of the red samples is R. tinctorum. However, as explained in the case
of cochineal, there is a high number of factors that can
affect the final dyestuff composition observed in a chromatographic analysis, including the natural variability in
the chemical composition of the madder root, the dye
extraction and preparation procedures, the effects of ageing and the analytical protocol adopted. Although distinctions can generally be made for non-aged reference
materials [23, 40], the unequivocal identification of the
precise botanical source used to prepare the madder dye
is not always straightforward when it comes to historical
samples. For these reasons, even if R. tinctorum is probably the source of this red dye [20], we decided to refer to
it with the general term madder.
In addition to red dyes, most red samples contained
a source of tannins, as highlighted by the detection of
ellagic acid (λmax = 368 nm; [M–H]− at m/z 301). Ellagic
acid is a common breakdown product of hydrolysable
tannins and does not enable the specific source of tannins to be distinguished. During dyeing, tannins can be
used to weight silk, as vegetable mordant, or to adjust the
shade of the color [66, 67]. Ellagic acid was detected in
very variable relative amounts (ca. 1–30%) always in combination with red dyes, and not in yellow, blue or green
samples, which suggests the use of tannins to adjust the
depth of the red color. A certain correspondence was in
fact found between darker shades of red, including purple, and higher amounts of tannins.
Natural yellow dyes
The FORS spectra obtained from most yellow areas did
not show any particular feature useful for the non-invasive identification of the yellow dyes (Fig. 2b). It is, in fact,
known that only a few yellow dyes (mostly carotenoids)
produce distinctive electronic spectra, whereas in all
other cases FORS is not suitable for any differentiation
[52, 53, 68].
By contrast, HPLC analysis enabled the botanical sources of these yellow dyes to be identified. In the
vast majority of the cases, larkspur (Delphinium semibarbatum) was identified based on the presence of
kaempferol-3-O-glycoside (λmax = 348 nm; [M–H]− at
m/z 447), quercetin-3-O-glycoside (λmax = 352 nm;
[M–H]− at m/z 463) and isorhamnetin-3-O-glycosides
(λmax = 356 nm; [M–H]− at m/z 477) (Fig. 3b) [26, 38].
In addition to the larkspur components, the yellow samples of S2004.66, S2004.78, S2004.80, S2004.90, S2004.92
Tamburini et al. Herit Sci
(2020) 8:114
Page 18 of 27
and 2007.35 also contained quercetin-3-O-rutinoside
(rutin; λmax = 354 nm; [M–H]− at m/z 609) and kaempferol 3-O-rutinoside (λmax = 352 nm; [M–H]− at m/z
593), which are molecular markers for the use of pagoda
tree flower buds (Sophora japonica) [32, 40] (Fig. 3b).
These sources of yellow dyes are in agreement with
previous analyses [19]. However, an additional yellow
dye was identified in one sample from an orange area
of S2004.78. In addition to rutin, this sample contained
quercetin-3-O-glucuronide (λmax = 354 nm; [M–H]− at
m/z 477). This molecular combination is reported for
grape vine leaves (Vitis vinifera), a yellow dye that has
been traditionally used, at least on a small scale, in Iran
and Turkey [26].
respectively [1, 9]. This order of dye application is only
possible using the traditional method of indigo dyeing,
which is performed at relatively low temperature (50 °C
max) and mild alkaline conditions [1, 69]. In modern
practice, the indigo vat is often created using chemicals
such as sodium dithionite and sodium/potassium sulfate/
carbonate, which raise the pH to approximately 12 and
higher temperature is required [28, 70]. In these conditions, previously applied red and yellow dyes can be easily removed, therefore the order of over-dyeing implies
the use of indigo first [70]. The order of application would
be an interesting area of further investigation and a possible tool to distinguish indigo dyeing carried out using the
natural or chemical process.
Natural blue dyes
Synthetic dyes
The reflectance spectra of most blue areas showed the
characteristic steep inflection point of indigo, which
occurs at ca. 720 nm [47] (Fig. 2c). Indigo is produced by
several plants, including Indian indigo (Indigofera tinctoria), woad (Isatis tinctoria), Chinese indigo (Polygonum tinctorium) and Strobilanthes cusia among many
others. However, all the indigo-producing plants yield
the same mixture of colorant molecules and therefore
cannot be chemically distinguished. Among these molecules, isatin (λmax = 420 nm; [M+H]+ at m/z 148),
indigotin (λmax = 620 nm; [M+H]+ at m/z 263), indirubin
(λmax = 550 nm; [M+H]+ at m/z 263), pseudoindirubin
(λmax = 440, 550 nm; [M−H]− at m/z 500) and a few other
not fully characterized indigoids were detected in all blue
(and blue-containing) samples by HPLC analysis (Fig. 3c).
Pseudoindirubin has been proposed as a hypothetical
marker for woad [62]. However, other indigo-producing
plants, although not typically Asian, contain this molecule, and an ultimate confirmation of the indigo source is
therefore not obtainable [62]. Nevertheless, it is reported
that indigo was mostly imported from China to Central
Asia [9].
The possible presence of synthetic dyes was suspected
based on the reflectance spectra obtained for certain
areas. In particular, the green and some of the blue areas
of S2004.79, S2004.82, S2004.85, S2004.89 and S2007.30
produced reflectance spectra that easily enabled the presence of indigo to be excluded. A maximum absorption
between 610 and 630 nm was observed (Fig. 4a–c) and
this is reported to be typical of several green and blue triarylmethine dyes [71]. The reflectance spectra obtained
for the green areas of S2004.90 revealed a possible mixture of indigo and synthetic dyes, as both an inflection
point at 720 nm and a maximum absorption at 580 nm
were observed (Fig. 4d). Some purple and red areas of
the same textiles also produced reflectance spectra not
corresponding to any natural dye. In these cases, it was
more difficult to attribute the spectra to a specific class
of synthetic dyes (Fig. 4f ), except for the red/purple color
of S2004.89, for which the maximum absorbance around
570 nm suggested the possible presence of a triarylmethine violet (Fig. 4e).
HPLC–DAD-MS analysis revealed again a more complex picture. In the green areas of the textiles S2004.79,
S2004.82, S2004.85, S2004.89 and S2007.30, diamond
green B, also referred to as malachite green or basic
green 4 (C.I. 42000), was identified based on the presence of its main component (λmax = 622 nm; [M+H]+
at m/z 329) and a series of mono-demethylated
(λmax = 608 nm; [M+H]+ at m/z 315), bis-demethylated
(λmax = 594 nm; [M+H]+ at m/z 301) and tri-demethylated (λmax = 580 nm; [M+H]+ at m/z 287) derivatives
(Fig. 5), in agreement with literature data [38, 63, 64].
Several isomers were detected, corresponding to different demethylated positions.
The red area of S2004.84 and the red and purple areas
of S2007.30 were found to contain fuchsine (basic violet
14, C.I. 42510) and the identification was based on the
presence of three compounds, respectively corresponding
Natural purple, green and orange colors
All the mixed colors were composed of mixtures of the
red, yellow and blue dyes identified and discussed in the
previous sections. For natural green and purple colors,
the identification of indigo was obtained by FORS
(Fig. 2d) and confirmed by HPLC analysis. When both
pure and mixed colors were present on the same textile, the red and yellow dyes mixed with indigo were the
same that were used for the pure red and yellow areas,
suggesting that red and yellow colors were applied from
the same dye bath. This is in agreement with the description of the ikat dyeing process, in which blue is applied
as the last color, both on undyed areas and overlaid on
yellow and red areas to obtain green and purple shades
Tamburini et al. Herit Sci
(2020) 8:114
Page 19 of 27
80
green S2004.79
a
70
b
blue S2004.82
70
60
60
40
Reflectance %
Reflectance %
50
610
30
50
40
20
30
10
20
0
400
50
500
600
700
Wavelength (nm)
c
800
900
10
400
blue S2004.89
600
700
Wavelength (nm)
800
900
green S2004.90
70
Refectance %
40
710
35
30
615
25
50
40
30
15
20
10
10
5
720
60
20
580
0
400
50
500
e
600
700
800
900
Wavelength (nm)
red/purple S2004.89
400
35
40
500
600
700
Wavelength (nm)
800
900
purple S2007.30
f
30
25
30
700
Reflectance %
Reflectance %
500
d
80
45
Reflectance %
630
20
570
10
20
15
555
575
10
5
0
0
400
500
600
700
Wavelength (nm)
800
900
400
500
600
700
Wavelength (nm)
800
900
Fig. 4 Reflectance spectra acquired by FORS, showing the possible presence of (a) a triarylmethine green dye, (b, c) a triarylmethine blue dye, (d) a
mixture of indigo and an unidentified green dye, (e) a triarylmethine purple dye, (f) an unidentified purple dye
to the fuchsine molecule, also referred to as rosaniline or
Magenta I, (λmax = 546 nm; [M+H]+ at m/z 302) and the
homologues with one additional methyl group (Magenta
II; λmax = 548 nm; [M+H]+ at m/z 316) and two additional methyl groups on the aromatic rings (Magenta
III, λmax = 550 nm; [M+H]+ at m/z 330) (Fig. 6), also in
agreement with published data [38, 44, 63, 64].
Methyl violet (basic violet 1, C.I. 42535), was identified in the purple and red areas of S2004.89. A complex chromatographic profile was obtained, showing
Tamburini et al. Herit Sci
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Page 20 of 27
mAU
50
λmax = 594 nm
λmax = 608 nm
mAU
75
50
25
75
25
0
a
mAU
10
50
λmax = 580 nm
0
300 400 500 600 700 nm
300 400 500 600 700 nm
5
mAU
λmax = 622 nm
mAU
50
25
0
25
0
300 400 500 600 700 nm
300
400
500
600
700 nm
0
10.0
Relative abundance
100
b
15.0
20.0
Retention time (min)
25.0
30.0
m/z 287 (+) = tridemethylated malachite green
m/z 301 (+) = bisdemethylated malachite green
m/z 315 (+) = monodemethylated malachite green
m/z 329 (+) = malachite green
0
10.0
15.0
20.0
Retention time (min)
25.0
30.0
Fig. 5 Chromatographic profiles obtained by HPLC–DAD-MS analysis of a green sample from the ikat textile S2004.85: (a) UV–Vis chromatogram
extracted at 600 nm (inserts show the UV–Vis absorbance spectra of the main compounds); (b) extract ion chromatograms obtained by using the
m/z values corresponding to the molecular ions [M+H]+ of malachite green components
the same compounds discussed for fuchsine and additional higher homologues of pararosaniline, containing three (λmax = 568 nm; [M+H]+ at m/z 330), four
(λmax = 576 nm; [M+H]+ at m/z 344), five (λmax = 583 nm;
[M+H]+ at m/z 358) and six (λmax = 588 nm; [M+H]+
at m/z 372) N-methyl groups. Additionally, at least two
isomers were detected for the compounds with three,
four and five N-methyl groups (Fig. 7). These observations were again in agreement with previous works on
the characterization of methyl violet [44, 63], although
the lack of tandem mass spectrometry detection did not
allow us to precisely assign the various isomers.
The red and green areas of S2004.81, the purple, red
and yellow areas of S2007.30 and the purple areas of
S2007.35 contained rhodamine B (basic violet 10, C.I.
45170). In the case of textiles S2004.81 and S2007.35,
two compounds were detected and identified as rhodamine B (λmax = 558 nm; [M+H]+ at m/z 443) and
the molecule corresponding to the loss of one N-ethyl
group (λmax = 544 nm; [M+H]+ at m/z 415) (Fig. 8).
Rhodamine B is known to easily photo-degrade and
the loss of N-ethyl groups is reported [72]. In the case
of S2007.30, in addition to these two compounds, two–
three additional peaks were detected with very similar
UV–Vis absorption spectra to the ones of rhodamine B,
but slightly lower λmax (ca. 530 nm), which matched with
the possible presence of rhodamine 6G (basic red 1, C.I.
45160) [64] or additional photo-oxidation products of
rhodamine B [72]. Although the retention times closely
matched with the compounds present in a reference of
rhodamine G, it was not possible to confirm the masses
of these compounds by HPLC–DAD-MS, therefore the
identification of rhodamine 6G remains tentative.
In a few other cases, some molecules were detected and
possibly related to the presence of synthetic dyes, but a
full identification was not possible. In a blue sample from
S2004.79, in addition to indigoids, one molecule was
detected, whose UV–Vis spectrum (λmax = 444 nm) and
retention time were similar to (but not perfectly matched)
the reference of the azo dye orange IV (acid orange 5, C.I.
Tamburini et al. Herit Sci
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Page 21 of 27
λmax = 548 nm
[M]+ = 316 m/z
mAU
10
5
1.5
0
a
300
400
500
mAU
(x10)
700
nm
λmax = 550 nm
[M]+ = 330 m/z
mAU
10
mAU
600
λmax = 546 nm
[M]+ = 302 m/z
1.0
1.0
5
0.5
0.5
0
300
400
500
600
700
nm
0.0
300
400
500
600
700
nm
0.0
5.0
Relative abundance
100
b
10.0
15.0
20.0
25.0
Retention time (min)
30.0
35.0
40.0
m/z 302 (+) = methyl-pararosaniline (rosaniline, fuchsine, magenta I)
m/z 316 (+) = dimethyl-pararosaniline (magenta II)
m/z 330 (+) = trimethyl-pararosaniline (magenta III)
0
10.0
12.5
15.0
17.5
20.0
Retention time (min)
22.5
25.0
27.5
Fig. 6 Chromatographic profiles obtained by HPLC–DAD-MS analysis of a red sample from the ikat textile S2004.84: (a) UV–Vis chromatogram
extracted at 550 nm (inserts show the UV–Vis absorbance spectra of the main compounds); (b) extract ion chromatograms obtained by using the
m/z values corresponding to the molecular ions [M+H]+ of fuchsine components
13080) [63, 64]. The mass of the pseudomolecular ion or
any other ion related to the molecule were not detected.
In a purple-green sample from S2004.84, in addition to
the molecular components of larkspur, cochineal and
indigo, four molecules were detected with low relative
abundance. The obtained UV–Vis spectra were not of
high quality due to the low concentrations, but for two
of the molecules a similarity with the UV–Vis spectra of
orange I (acid orange 20, C.I. 14600) (λmax = 480 nm) and
orange II (acid orange 7, C.I. 15510) (λmax = 488) nm was
respectively observed [63, 64]. Nevertheless, the masses
of none of these molecules were detected by MS, therefore this possible mixture of azo dyes is only tentatively
identified. Finally, in a blue-green sample from S2004.82
and in a green sample from 2007.30, in addition to malachite green, four additional molecules were detected.
Three of these molecules were present as a triplet and the
UV–Vis spectra (λmax = 593, 607, 620 nm respectively)
and retention times matched with the compounds present in the triarylmethine dye patent blue V (acid blue 3,
C.I. 42051) [63, 64]. The fourth molecule showed a UV
spectrum (λmax = 352 nm) and a retention time matching
alizarin yellow GG (mordant yellow 1, C.I. 14025). As it
was not possible to repeat the analysis with HPLC–DADMS to confirm the mass of these molecules, these identifications also remain tentative.
Tamburini et al. Herit Sci
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Page 22 of 27
λmax = 568 nm
[M]+ = 330 m/z
mAU
1.5
mAU
2
1.0
mAU
2
λmax = 563 nm
[M]+ = 316 m/z
1
0.5
0
300 400 500 600 700 nm
0.0
mAU
a
300 400 500 600 700 nm
1
λmax = 583 nm
[M]+ = 358 m/z
mAU
10
0
2
λmax = 576 nm
[M]+ = 344 m/z
300 400 500 600 700 nm
5
1
0
300 400 500 600
700 nm
0
20.0
b
Relative abundance
100
22.5
25.0
27.5
Retention time (min)
30.0
32.5
m/z 316 (+) = N-dimethyl-pararosaniline
m/z 330 (+) = N-trimethyl-pararosaniline
m/z 344 (+) = N-tetramethyl-pararosaniline
m/z 358 (+) = N-pentamethyl-pararosaniline
m/z 372 (+) = N-hexamethyl-pararosaniline
0
26.0
26.5
27.0
27.5
28.0
Retention time (min)
28.5
29.0
29.5
Fig. 7 Chromatographic profiles obtained by HPLC–DAD-MS analysis of a purple sample from the ikat textile S2004.89: (a) UV–Vis chromatogram
extracted at 550 nm (inserts show the UV–Vis absorbance spectra of the main compounds); (b) extract ion chromatograms obtained by using the
m/z values corresponding to the molecular ions [M+H]+ of methyl violet components
Discussion
It appeared from the results of this research that the
natural sources of dyes were mostly in agreement with
local dyes used in Central Asia in the nineteenth century [1, 20, 38]. The only exception is represented by
the yellow dye extracted from grape vine leaves (Vitis
vinifera), which was identified in one sample from textile S2004.78. This ikat is the only known example of an
uncut complete loom length textile, and it is a velvet,
showing some orange pile warps as a repeating pattern.
These warps are the ones containing the grape vine
leaves dye, which is reported to be used in Iran and
Turkey [26]. Considering that Iran has an ikat tradition,
an Iranian influence is hypothesized for this textile.
However, the design confidently places the textile as a
Central Asian piece (Pers. Comm., Massumeh Farhad
and Sumru Belger Krody, 2020), therefore it is more
likely that the dye (or dyers) had come from the Mediterranean area rather than the textile being produced in
Iran. Interestingly, textile S2004.85, which is attributed
to Iranian manufacture, did not show the presence of
this dye.
Additionally, S2004.89 and S2004.92 were previously
investigated and the results of the dye analysis were presented in Wouters’ Appendix II in “Ikat: Silks of Central
Asia, The Guido Goldman Collection” as numbers 369
and 309, respectively [20]. Our results are in good agreement with these previous analyses and we were able to
report the identification of the synthetic dye (methyl violet) previously suspected in S2004.89 (Table 1). No other
textiles were analyzed in both studies.
Red colors were very rarely produced using only one
dye. Cochineal appears to be the main red dye, but
Tamburini et al. Herit Sci
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Page 23 of 27
λmax = 558 nm
[M]+ = 443 m/z
mAU
4.0
a
mAU
2
λmax = 544 nm
[M]+ = 415 m/z
3.0
2.0
7
1.0
1
0.0
mAU
6
300
400
500
600
700
nm
0
5
300
400
500
600
700
nm
4
10.0
Relative abundance
100
b
12.5
15.0
17.5
20.0
Retention time (min)
22.5
25.0
27.5
m/z 443 (+) = rhodamine B
m/z 415 (+) = N-deethylated rhodamine B
0
10.0
12.5
15.0
17.5
20.0
Retention time (min)
22.5
25.0
27.5
Fig. 8 Chromatographic profiles obtained by HPLC–DAD-MS analysis of a red sample from the ikat textile S2004.81: (a) UV–Vis chromatogram
extracted at 550 nm (inserts show the UV–Vis absorbance spectra of the main compounds); (b) extract ion chromatograms obtained by using the
m/z values corresponding to the molecular ions [M+H]+ of rhodamine B components
madder and lac dye were often added as well. Madder is
actually mentioned as the original red dye in the region
[1], lac was mostly imported from India or China, and
cochineal come from America through Europe, thus
revealing a dynamic scenario. It was particularly interesting to notice that the textiles containing the highest
percentage of madder (S2004.83 and S2004.91) are also
considered among the oldest ones and are attributed to
the first half of the nineteenth century. If this interpretation is correct, the results may point towards a progressive replacement of madder by cochineal during the
course of the century. More data are needed to confirm
this hypothesis. It is also difficult to establish at which
stage of the ikat production these mixtures were created.
It might have been a deliberate choice of the dyers, or
such mixtures might have been prepared by merchants
and sold to the dyers. In addition, residual dyes from
previous dye baths cannot be excluded. Regardless of the
ultimate answer, it has to be borne in mind that by the
second half of the nineteenth century ikat production
was at its highest point and constituted a business, which
involved many different professionals and stages of production. However, the economic scenario was not good.
Reducing costs by looking for cheaper alternatives must
have been a driving force during ikat production.
Out of the 26 ikat textiles analyzed, 9 were found to
contain early synthetic dyes. Fuchsine, methyl violet,
malachite green and rhodamine B were synthesized in
1856, 1861, 1877 and 1887 respectively [18]. Among the
other synthetic dyes tentatively identified, orange I and
orange II were synthesized in 1876, alizarin yellow GG in
1887, patent blue V in 1888, and rhodamine 6G in 1892
[18]. The ikats S2004.79 and S2004.85 were attributed to
1850–1900, but the presence of malachite green moves
the possible production date of these textiles to at least
the last quarter of the nineteenth century. For S2004.81
and S2007.35, originally attributed to 1825–1875 and
mid-nineteenth century respectively, the presence of
rhodamine B significantly moves the possible production
date to after 1887. S2004.89 and S2007.30 were attributed
Tamburini et al. Herit Sci
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to 1850–1875, but for the former, the presence of both
methyl violet and malachite green moves the possible
production date to after 1877, whereas for the latter, the
detection of several synthetic dyes, including rhodamine
B (and possibly rhodamine 6G), moves the possible production date to at least the end of the nineteenth century.
S2004.82 and S2004.84 and S2004.90 were already attributed to 1875–1900 and the presence of synthetic dyes
confirms a relatively late production of these textiles. The
presence of the tentatively identified dyes does not affect
the refined dating of these textiles and additional analyses
are foreseen, possibly using HRMS and/or MS/MS detectors, in order to confirm the identification by considering
additional samples from these textiles (such as the blue
from S2004.89 and the green from S2004.90) and other
ikats in the collection. It is also worth underlining that,
as some time inevitably passed between the commercialization of these synthetic dyes in Europe and their export
and use in Central Asia, some of the ikats containing synthetic dyes may have been produced at the beginning of
the twentieth century.
The early synthetic dyes detected are in agreement with
other studies that scientifically confirm the introduction
of the same classes of synthetic dyes to Central Asia [38]
and China [36] by the late nineteenth century-early twentieth century. It also appears that green, purple and blue
synthetic dyes were most commonly used during this
transition phase in agreement with these colors being
more difficult to obtain using natural dyes, whereas red
and yellow dyes seem to remain natural for a longer time,
with the exception of some pink shades obtained with
rhodamine and fuchsine.
Additionally, it was interesting to notice that in no case
the textiles were entirely dyed with synthetic dyes. Mixtures of natural and synthetic dyes were used not just in
the same textile, but even to produce a single color, and
this represents a rare window into the transitional and
experimental phase that dyers experienced in the late
nineteenth century. Guido Goldman’s intention to only
buy naturally-dyed ikats is likely to have been shared
by many other early buyers, who did not appreciate the
flashy and unnatural colors produced by synthetic dyes.
Dyers might have initially tried to adjust the color shades
by mixing natural and cheaper synthetic dyes to mimic
natural dyes, and, as synthetic dyes were also already
known not to be particularly lightfast, mixing a percentage of natural dyes would have made the color last
longer. The use of mixtures of natural and synthetic dyes
for labor or cost savings follows what we assume to be an
established practice in the production of ikats: the red
dye cochineal, found in all the ikats analyzed, while a natural dye, was identified as imported American cochineal,
Page 24 of 27
supporting a history of the use of imported dyes and,
similarly to the synthetics, was used as a mixture with
other red dyes.
A final contextualization of the results was attempted
in the light of the common stylistic assumption that more
complex designs with more colors are dated earlier than
simpler, larger and more graphic ones. This assumption
has its roots into the worsening of the economic situation towards the end of the nineteenth century. While
the demand for ikat production was increasing, dyers and
weavers had less means and time to fulfill such demand.
The reduction of the complexity and labor intensity of
the ikat production was a natural outcome and translated into larger, more stylized designs obtainable by
binding the threads less frequently. Among the textiles
under investigation, some complex and intricate designs
are present, e.g. S2004.75, S2004.76, S2004.83, S2004.91,
2006.20, 2006.21, and the four robes (Table 1). In none
of these textiles were synthetic dyes detected, which does
not confirm a precise production date, but partially supports a possible early one. On the other hand, the textiles
containing synthetic dyes all exhibit relatively simple
designs. However, among the naturally-dyed textiles,
some relatively simple motifs are present as well, e.g.
S2004.66, S2004.78, S2004.88, S2004.92, etc. Therefore,
although a good correspondence was found between simpler motifs possibly being produced later, further investigation would be useful to expand on this topic.
Conclusions
Dye analysis was carried out on 26 Central Asian ikat
textiles from the Arthur M. Sackler Gallery collection
mostly attributed to the second half of the nineteenth
century.
The study represents a valuable example of the importance of combining non-invasive and invasive analysis. In
fact, although FORS gave an overview of the presence and
distribution of some dyes, including indigo, insect-based
red dyes and synthetic dyes, HPLC analysis on selected
samples revealed complex mixtures of dyes, partially as
a result of the ikat dyeing process, which were not highlighted non-invasively. DAD detection was suitable to
identify most sources of natural dyes, but MS proved fundamental to confirm their presence and further identify
some of the synthetic dyes.
Three main sources of red natural dyes and three
main sources of yellow natural dyes were identified,
namely for reds: cochineal, madder, lac, and for yellows: larkspur, pagoda tree flower buds and grape vine
leaves, with cochineal and larkspur being the most
common ones. Indigo was used for all the natural blue
shades, and tannins were used to adjust the color of
Tamburini et al. Herit Sci
(2020) 8:114
the red shades. These dyes fit with the sources of color
reported to be available and in use in Central Asia in
the nineteenth century. The identification of early synthetic dyes, namely fuchsine, methyl violet, malachite
green and rhodamine B, was fundamental to adjust the
dating of the 9 textiles in which they were detected.
Additional synthetic dyes, including early mono-azo
dyes, were tentatively identified and future research
will be dedicated to analyze more samples from Central
Asian ikats and compare the results. The use of tandem
mass spectrometry is also foreseen as an additional tool
for a more accurate molecular identification.
In addition to underlining the importance of scientific analysis to support art historical interpretation,
this study creates a window on a dynamic dyeing scenario, in which dyers were experimenting and adjusting
during a period of economic and technological change.
Abbreviations
FORS: Fiber optic reflectance spectroscopy; HPLC: High pressure liquid chromatography; DAD: Diode array detector; MS: Mass spectrometry; HRMS: High
resolution mass spectrometry; C.I.: Color index; UV: Ultraviolet; Vis: Visible; MSI:
Multispectral imaging; λmax: Maximum wavelength; m/z: Mass to charge ratio.
Acknowledgements
The authors would like to thank Jan Wouters for providing expertise on dye
analysis that was instrumental in getting the project underway; Massumeh
Farhad (Chief Curator and The Ebrahimi Family Curator of Persian, Arab, and
Turkish Art, Freer Gallery of Art and Arthur M. Sackler Gallery, National Museum
of Asian Art, Smithsonian Institution, Washington DC, USA), Sumru Belger
Krody (Senior Curator, George Washington University Museum and The Textile
Museum, Washington DC, USA) and Mary Ballard (Senior Textile Conservator,
Museum Conservation Institute, Smithsonian Institution, Washington DC, USA)
for useful discussions; Morgan Meador for her work on the ikats motifs; the
Gaddy family for enabling data transfer.
Esther Méthé (formerly George Washington University Museum and The
Textile Museum, Washington DC, USA), and Mary Ballard provided reference
materials produced at dye analysis workshops conducted by Dr. Helmut
Schweppe held at the former Smithsonian Conservation Analytical Laboratory.
References of natural dyes were made available by the Getty Conservation
Institute from materials produced during their Asian Organic Colorants project
(2006-2010, https://www.getty.edu/conservation/our_projects/science/asian
/index.html).
This work was supported by the Smithsonian Institution Postdoctoral Fellowship program, which funded Dr. Diego Tamburini’s fellowship.
Authors’ contributions
DT was responsible for overall data interpretation and drafting of the article;
CM was responsible for acquisition of HPLC–DAD-MS data; EB was responsible
for sampling, and acquisition and interpretation of HPLC–DAD data; TK was
responsible for acquisition of FORS data; MLC was responsible for supporting
lab activities; BM was responsible for conception and design of the study. All
authors read and approved the final manuscript.
Funding
No specific source of funding was used for this research.
Availability of data and materials
The datasets used and/or analysed during the current study are available from
Dr. Blythe McCarthy and Dr. Matthew L. Clarke on reasonable request.
Competing interests
The authors declare that they have no competing interests.
Page 25 of 27
Author details
Department of Conservation and Scientific Research, Freer Gallery of Art
and Arthur M. Sackler Gallery, National Museum of Asian Art, Smithsonian
Institution, 1050 Independence Ave SW, Washington, DC 20560, USA. 2 Present
Address: Department of Scientific Research, Metropolitan Museum of Art,
1000 5th Ave, New York, NY 10028, USA. 3 Present Address: National Institute
of Technology, Fukui College, Geshi-cho, Sabae, Fukui 916-8507, Japan.
4
Present Address: National Ainu Museum, 2-3-1 Wakakusa-cho, Shiraoicho,
Hokkaido, Japan.
1
Received: 14 July 2020 Accepted: 22 September 2020
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