Heldal, T. og Storemyr, P. 2018. Forvaltning av historiske steinbrudd: Innspill til nasjonal strategi Rapport til Riksantikvaren fra Musea i Sogn og Fjordane, avd. Norsk Kvernsteinsenter, Hyllestad. Kvernsteins¬parkens skrifter, 4, 44 s., 2018
Steinbrudd kan ha stor historisk betydning, enten i kraft av deres egenverdi, i kraft av deres br... more Steinbrudd kan ha stor historisk betydning, enten i kraft av deres egenverdi, i kraft av deres bruk i historiske byggerier eller som kilde til steintyper av betydning for å vedlikeholde bygningsverdier og kulturlandskap. Forvaltning av steinbrudd og kunnskapen om dem er i beste fall fragmentert, i mange tilfeller svært mangelfull eller fraværende. Det fører til at viktige verneverdier forsvinner fortløpende. I tillegg skaper manglende kunnskap om steinbrudd og steinforekomster problemer knyttet til restaurering av arkitekturarven. Vi har allerede akutte problemer innen restaurering av middelalderbygninger. Når restaureringsbehovene melder seg for alvor for bygninger fra slutten av 1800-tallet og begynnelsen av 1900-tallet vil problemet bli betydelig.
Informasjon om steinbrudd og bruk er fragmentert og ikke organisert på en måte som bringer denne kunnskapen ut til de som har behov for den. Etter-reformatoriske steinbrudd er dårlig ivaretatt og mange står i stor fare for å bli utilgjengelig/ødelagt for fremtiden. Småskala produksjon av stein, inklusive uttak av restaureringsstein, er gjennom statlig sanksjon og lovverk blitt vanskelig. Det medfører også tap av håndverk og historisk viktige kilder for stein. Lovverk og etablert praksis er lite egnet til å kunne kombinere vern og drift.
Som et resultat av disse forholdene, er vi i Norge i ferd med å «male oss inn i et hjørne» der vi både ødelegger viktige kulturminner og gjør oss ute av stand til å kunne restaurere og konservere byggverk på en god måte i fremtiden. Derfor har vi behov for et strategisk program om stein og steinbrudd, for å løfte kunnskapen, styrke veiledning og forbedre forvaltningspraksis.
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Soapstone is a remarkable rock. While it is soft and very workable, it is also durable and heat-resistant, and with a high heat-storage capacity. These properties have been recognised and valued around the world since prehistoric times, and soapstone has been used for a multitude of purposes, ranging from everyday household utensils to prestigious monuments and buildings. This book addresses soapstone use in Norway and the North Atlantic region, including Greenland. Although most papers deal with the Iron Age and Middle Ages, the book spans the Mesolithic to the early modern era. It deals with themes related to quarries, products and associated people and institutions in a broad context. Recent years have seen a revival of basic archaeological and geological research into the procurement and use of stone resources. With its authors drawn from the fields of archaeology, geosciences and traditional crafts, the anthology reflects cross-disciplinary work born of this revival.
Denne boken er en kulturhistorisk reise i stein. Med fokus på Nidarosdomen går ferden fra eldgamle steinbrudd ved Nilens bredder, over Middelhavet og nordover. Men det stopper ikke her. Nidarosdomen gikk nesten i grus for 500 år siden. Siden reiste den seg som symbol for det moderne Norge. Til gjenreisinen gikk det med tusenvis av tonn med stein fra hele landet. 110 steinbrudd ble testet, 70 brudd kom i bruk. I denne boken får du vite hvorfor.
Per Storemyr har jobbet med Nidarosdomens stein i 25 år. Han har 20 feltsesonger bak seg i Egypts gamle steinbrudd og har fartet fra brudd til brudd ellers i verden, alltid med samme spørsmål: Hvordan ble det jobbet i bruddene i gamle dager? Hvem sto bak slitet i berget det blå?
-
Her er et lite utdrag av boken, som du kan kjøpe i bokhandlernes nettbutikker, f.eks. https://www.norli.no/nidarosdomens-grunnfjell
Papers by Per Storemyr
There are only a few foreign, decorative stone elements at the cathedral – all made from soapstone of still unknown provenance. It is easy to point to Norway with its great soapstone traditions and because the Faroes were part of the Norwegian Archbishopric in the Middle Ages. However, it is hard to find visually matching soapstone types in Norway. The soapstone might have come from Shetland, which also have long soapstone traditions.
There is no limestone for making lime mortar on the Faroe Islands. We discuss how quicklime was manufactured from burning seashell. Historically, Kirkjubøur is not known for significant shell deposits and deposits farther away will have been taken in use. One of the candidates was used for lime burning until the early 20th century.
The practice of burning seashells for lime is interesting because this tradition hardly originates in Norway, where burning marble and limestone dominated in the Middle Ages. Influences rather must be sought elsewhere, not least on the islands off the coast of Scotland, which are well known for this practice.
With soapstone and lime indicators not easily pointing to Norway, we hypothesize that influences related to material procurement and craftsmanship – and craftsmen – may well have come from the British Isles/Scotland. This is in line with architectural and stylistic traits of the cathedral, discussed by other authors in the edited volume.
Storemyr, P. & Árting, U. (2024): The Stones and Mortars of the Faroese Medieval Cathedral. In Eliasen, K.S. & Stige, M. (eds.) The Cathedral of Kirkjubøur and the Medieval Bishop’s See of the Faroes. Tórshavn: Tjóðsavnið, pp. 301-328
Tansem, K. & Storemyr, P. (2020). Red-coated rocks on the seashore: The esthetics and geology of prehistoric rock art in Alta, Arctic Norway. Geoarchaeology, early view, open access, 1–21. https://doi.org/10.1002/gea.21832
«True» marble (metamorphic limestone) was commonly used for ashlar and decoration in medieval churches in West Norway, especially in the middle part of the country (regions Møre and Trøndelag). The nearest European parallels can be found in the alpine region and, of course, in Italy. This is due to geological circumstances, with Central Europe and the British Isles almost devoid of true marble. In a Norwegian context, Gildeskål is nevertheless special. As one of two medieval churches, it is built directly on marble bedrock. This bedrock is part of a whole range of Cambro-Silurian limestone deposits in Nordland county, which were later transformed to marble during the Caledonian orogeny (mountain building process), about 400 million years ago. Renowned Fauske marble occurs in another regional marble belt, about 60 km east of Gildeskål, and has delivered stone for the international market since the 19th century.
The Gildeskål marble is banded, medium-grained, with calcite as the most important constituent. It contains smaller amounts of other minerals, such as mica, amphibole, quartz, graphite and pyrite. Hence, at a distance the colour appears off-white to greyish, with poorer varieties grading into dark grey, especially close to intercalated mica schist.
Since the marble deposit displays sub-horizontal, often open cleavage and is penetrated by vertical cracks at suitable intervals, it was easy for the medieval quarrymen to break loose or wedge out blocks. These are typically less than half a metre high and often more than a metre long. The stone thus is a good ragstone and minimal hewing was necessary to produce quite regular building blocks. The most homogeneous and whitest varieties are also suitable as a source for regular ashlar.
No medieval quarry has yet been found, but there can be little doubt that the marble was quarried in the near vicinity, perhaps by the shoreline, a few hundred metres to the west of the church. Old quarries may be hidden under vegetation, but it is also possible that stone was just broken loose from surface layers and even collected by the shore, thus leaving minimum traces of true extraction.
On studying the masonry, it becomes clear that the craftsmen carefully sorted the available stone in the surroundings. The best pieces went to ashlar (and a few decorative details), which was mainly put in use in the second building phase.
This phase comprised the upper part of the choir and parts of the nave. The first building phase, which may have followed a master plan laid out for the whole church, is characterised by good ragstone masonry. However, studies have shown that the western part of the nave may have a more complex building history; perhaps as a result of one or two fires (the last fire took place in 1710). Especially the west facade shows signs of heavy repair and is also built in another fashion than the rest of the church, with more irregular, rubble-like stone.
That the building practice heavily changed over time is also evident in the south transept, which was added after the 1710 fire. This part is largely built from mica schist and marble rubble, which is easily available a few tens of metres to the east of the church. Such stone can also be found in interior gable walls in the medieval part of the church. The gable walls also display some blocks of gneiss, which were undoubtedly collected along the shore.
In summary, the study shows that the use of stone at Gildeskål church can be viewed in the light of three important factors: 1) Changing fashions and building practice, including the availability of competent masons and stone cutters (ragstone, ashlar and rubble masonry); 2) local stone availability (various marble qualities, mica schist and loose stones by the shore); 3) The targeted sorting of local stone aimed for different purposes.
Underground medieval quarries are rare, in Norway and elsewhere in Europe. Thus the question: Could a big underground soapstone quarry have been opened at Bakkaunet in Trondheim (central Norway) in the Middle Ages? This question of stone procurement for Nidaros Cathedral – which is Europe’s northernmost medieval cathedral and a building heavily influenced by English traditions and fashions – has bothered us for the last 20 years. In this paper we discuss what we think the quarrymen did. It is a biography of the now almost lost Bakkaunet quarry, with a focus on the question about underground operations. But the paper also discusses stone procurement for Nidaros Cathedral in view of contemporary international, especially English, trends. The story is sad, for the open-cast part of this once great quarry, very close to the centre of Trondheim, has been successively destroyed by modern house building over the last century.
Soapstone is a remarkable rock. While it is very workable due to a high content of talc, the softest known mineral in existence, it is also durable, heat-resistant and has a high heat storage capacity. These properties have been recognised and valued since prehistory across the world and soapstone has been used for a very broad range of products. This book addresses soapstone use in Norway and the North Atlantic region, including Greenland (here: the North). Although the majority of papers deal with the Iron Age and Middle Ages, the book spans the Mesolithic to the early modern era, dealing with themes related to quarries, products and associated people and institutions in a wide sense. Recent years have seen a revival of basic archaeological and geological research into the procurement and use of stone resources. With authors from the fields of archaeology, geosciences and traditional crafts, this anthology reflects cross-disciplinary work grown out of this revival.
presents features found in five Egyptian quarries and discusses these on a background of rock properties and possible quarrying technologies. Conclusively, it suggests that the use of fire in
stone quarrying reached a highly sophisticated level during the New Kingdom period.
Prior to the New Kingdom, stone in open-cut quarries was mainly extracted in a non-systematic manner with blocks removed individually or in small groups. From the New Kingdom onward, quarrying was usually done more systematically with multiple blocks extracted simultaneously on descending bedrock platforms, a method of quarrying which first appeared in the early Old Kingdom (about 2500 BC).
Stone extraction in the underground gallery quarries was similar in all periods with blocks removed sequentially from ceiling to floor along the walls.
The use of descending platforms and long chisels were major quarrying innovations. Although the former continued in use up until the present day, ancient Egyptian conservatism prevented the general adoption of quarrying tools more advanced than the chisel, such as picks.
-------
Unfortunately, the publisher does not allow us to upload the paper. But visit this website: http://per-storemyr.net/2015/05/20/new-ways-of-looking-at-highly-organised-stone-quarrying-in-ancient-egypt/ - and you will find a gallery of quarry images and addresses for obtaining a free PDF.
Reference:
Heldal, T., Storemyr, P., Bloxam, E. & Shaw, I. (2016): Gneiss for the Pharaoh: Geology of the Third Millennium BCE Chephren's Quarries in Southern Egypt. Geoscience Canada, 43, 63-78
The medieval marble quarries at Sparbu in Central Norway are part of a wider quarry landscape comprising soapstone quarries and possibly quern quarries with traditions back to the Iron Age. Hence it is likely that the marble quarries were found upon procurement of soapstone for vessels and perhaps garnet micaschist for rotary querns. Together with the Allmenningen marble quarry, the Sparbu quarries provided white marble for shafts, pillars, floor and tomb slabs to Nidaros Cathedral – the northernmost of Europe’s great medieval cathedrals. The cathedral is heavily infuenced by English medieval architecture and so is the use of marble. Marble for English cathedrals was provided from the famous Purbeck quarries with traditions back to the Roman Iron Age and beyond, but also from Frosterly and other places. In this paper the Sparbu quarries are compared with the Purbeck quarry landscape and it is argued that they can be viewed as a miniature version of their bigger sister.
life in ancient Egypt."
Soapstone is a remarkable rock. While it is soft and very workable, it is also durable and heat-resistant, and with a high heat-storage capacity. These properties have been recognised and valued around the world since prehistoric times, and soapstone has been used for a multitude of purposes, ranging from everyday household utensils to prestigious monuments and buildings. This book addresses soapstone use in Norway and the North Atlantic region, including Greenland. Although most papers deal with the Iron Age and Middle Ages, the book spans the Mesolithic to the early modern era. It deals with themes related to quarries, products and associated people and institutions in a broad context. Recent years have seen a revival of basic archaeological and geological research into the procurement and use of stone resources. With its authors drawn from the fields of archaeology, geosciences and traditional crafts, the anthology reflects cross-disciplinary work born of this revival.
Denne boken er en kulturhistorisk reise i stein. Med fokus på Nidarosdomen går ferden fra eldgamle steinbrudd ved Nilens bredder, over Middelhavet og nordover. Men det stopper ikke her. Nidarosdomen gikk nesten i grus for 500 år siden. Siden reiste den seg som symbol for det moderne Norge. Til gjenreisinen gikk det med tusenvis av tonn med stein fra hele landet. 110 steinbrudd ble testet, 70 brudd kom i bruk. I denne boken får du vite hvorfor.
Per Storemyr har jobbet med Nidarosdomens stein i 25 år. Han har 20 feltsesonger bak seg i Egypts gamle steinbrudd og har fartet fra brudd til brudd ellers i verden, alltid med samme spørsmål: Hvordan ble det jobbet i bruddene i gamle dager? Hvem sto bak slitet i berget det blå?
-
Her er et lite utdrag av boken, som du kan kjøpe i bokhandlernes nettbutikker, f.eks. https://www.norli.no/nidarosdomens-grunnfjell
There are only a few foreign, decorative stone elements at the cathedral – all made from soapstone of still unknown provenance. It is easy to point to Norway with its great soapstone traditions and because the Faroes were part of the Norwegian Archbishopric in the Middle Ages. However, it is hard to find visually matching soapstone types in Norway. The soapstone might have come from Shetland, which also have long soapstone traditions.
There is no limestone for making lime mortar on the Faroe Islands. We discuss how quicklime was manufactured from burning seashell. Historically, Kirkjubøur is not known for significant shell deposits and deposits farther away will have been taken in use. One of the candidates was used for lime burning until the early 20th century.
The practice of burning seashells for lime is interesting because this tradition hardly originates in Norway, where burning marble and limestone dominated in the Middle Ages. Influences rather must be sought elsewhere, not least on the islands off the coast of Scotland, which are well known for this practice.
With soapstone and lime indicators not easily pointing to Norway, we hypothesize that influences related to material procurement and craftsmanship – and craftsmen – may well have come from the British Isles/Scotland. This is in line with architectural and stylistic traits of the cathedral, discussed by other authors in the edited volume.
Storemyr, P. & Árting, U. (2024): The Stones and Mortars of the Faroese Medieval Cathedral. In Eliasen, K.S. & Stige, M. (eds.) The Cathedral of Kirkjubøur and the Medieval Bishop’s See of the Faroes. Tórshavn: Tjóðsavnið, pp. 301-328
Tansem, K. & Storemyr, P. (2020). Red-coated rocks on the seashore: The esthetics and geology of prehistoric rock art in Alta, Arctic Norway. Geoarchaeology, early view, open access, 1–21. https://doi.org/10.1002/gea.21832
«True» marble (metamorphic limestone) was commonly used for ashlar and decoration in medieval churches in West Norway, especially in the middle part of the country (regions Møre and Trøndelag). The nearest European parallels can be found in the alpine region and, of course, in Italy. This is due to geological circumstances, with Central Europe and the British Isles almost devoid of true marble. In a Norwegian context, Gildeskål is nevertheless special. As one of two medieval churches, it is built directly on marble bedrock. This bedrock is part of a whole range of Cambro-Silurian limestone deposits in Nordland county, which were later transformed to marble during the Caledonian orogeny (mountain building process), about 400 million years ago. Renowned Fauske marble occurs in another regional marble belt, about 60 km east of Gildeskål, and has delivered stone for the international market since the 19th century.
The Gildeskål marble is banded, medium-grained, with calcite as the most important constituent. It contains smaller amounts of other minerals, such as mica, amphibole, quartz, graphite and pyrite. Hence, at a distance the colour appears off-white to greyish, with poorer varieties grading into dark grey, especially close to intercalated mica schist.
Since the marble deposit displays sub-horizontal, often open cleavage and is penetrated by vertical cracks at suitable intervals, it was easy for the medieval quarrymen to break loose or wedge out blocks. These are typically less than half a metre high and often more than a metre long. The stone thus is a good ragstone and minimal hewing was necessary to produce quite regular building blocks. The most homogeneous and whitest varieties are also suitable as a source for regular ashlar.
No medieval quarry has yet been found, but there can be little doubt that the marble was quarried in the near vicinity, perhaps by the shoreline, a few hundred metres to the west of the church. Old quarries may be hidden under vegetation, but it is also possible that stone was just broken loose from surface layers and even collected by the shore, thus leaving minimum traces of true extraction.
On studying the masonry, it becomes clear that the craftsmen carefully sorted the available stone in the surroundings. The best pieces went to ashlar (and a few decorative details), which was mainly put in use in the second building phase.
This phase comprised the upper part of the choir and parts of the nave. The first building phase, which may have followed a master plan laid out for the whole church, is characterised by good ragstone masonry. However, studies have shown that the western part of the nave may have a more complex building history; perhaps as a result of one or two fires (the last fire took place in 1710). Especially the west facade shows signs of heavy repair and is also built in another fashion than the rest of the church, with more irregular, rubble-like stone.
That the building practice heavily changed over time is also evident in the south transept, which was added after the 1710 fire. This part is largely built from mica schist and marble rubble, which is easily available a few tens of metres to the east of the church. Such stone can also be found in interior gable walls in the medieval part of the church. The gable walls also display some blocks of gneiss, which were undoubtedly collected along the shore.
In summary, the study shows that the use of stone at Gildeskål church can be viewed in the light of three important factors: 1) Changing fashions and building practice, including the availability of competent masons and stone cutters (ragstone, ashlar and rubble masonry); 2) local stone availability (various marble qualities, mica schist and loose stones by the shore); 3) The targeted sorting of local stone aimed for different purposes.
Underground medieval quarries are rare, in Norway and elsewhere in Europe. Thus the question: Could a big underground soapstone quarry have been opened at Bakkaunet in Trondheim (central Norway) in the Middle Ages? This question of stone procurement for Nidaros Cathedral – which is Europe’s northernmost medieval cathedral and a building heavily influenced by English traditions and fashions – has bothered us for the last 20 years. In this paper we discuss what we think the quarrymen did. It is a biography of the now almost lost Bakkaunet quarry, with a focus on the question about underground operations. But the paper also discusses stone procurement for Nidaros Cathedral in view of contemporary international, especially English, trends. The story is sad, for the open-cast part of this once great quarry, very close to the centre of Trondheim, has been successively destroyed by modern house building over the last century.
Soapstone is a remarkable rock. While it is very workable due to a high content of talc, the softest known mineral in existence, it is also durable, heat-resistant and has a high heat storage capacity. These properties have been recognised and valued since prehistory across the world and soapstone has been used for a very broad range of products. This book addresses soapstone use in Norway and the North Atlantic region, including Greenland (here: the North). Although the majority of papers deal with the Iron Age and Middle Ages, the book spans the Mesolithic to the early modern era, dealing with themes related to quarries, products and associated people and institutions in a wide sense. Recent years have seen a revival of basic archaeological and geological research into the procurement and use of stone resources. With authors from the fields of archaeology, geosciences and traditional crafts, this anthology reflects cross-disciplinary work grown out of this revival.
presents features found in five Egyptian quarries and discusses these on a background of rock properties and possible quarrying technologies. Conclusively, it suggests that the use of fire in
stone quarrying reached a highly sophisticated level during the New Kingdom period.
Prior to the New Kingdom, stone in open-cut quarries was mainly extracted in a non-systematic manner with blocks removed individually or in small groups. From the New Kingdom onward, quarrying was usually done more systematically with multiple blocks extracted simultaneously on descending bedrock platforms, a method of quarrying which first appeared in the early Old Kingdom (about 2500 BC).
Stone extraction in the underground gallery quarries was similar in all periods with blocks removed sequentially from ceiling to floor along the walls.
The use of descending platforms and long chisels were major quarrying innovations. Although the former continued in use up until the present day, ancient Egyptian conservatism prevented the general adoption of quarrying tools more advanced than the chisel, such as picks.
-------
Unfortunately, the publisher does not allow us to upload the paper. But visit this website: http://per-storemyr.net/2015/05/20/new-ways-of-looking-at-highly-organised-stone-quarrying-in-ancient-egypt/ - and you will find a gallery of quarry images and addresses for obtaining a free PDF.
Reference:
Heldal, T., Storemyr, P., Bloxam, E. & Shaw, I. (2016): Gneiss for the Pharaoh: Geology of the Third Millennium BCE Chephren's Quarries in Southern Egypt. Geoscience Canada, 43, 63-78
The medieval marble quarries at Sparbu in Central Norway are part of a wider quarry landscape comprising soapstone quarries and possibly quern quarries with traditions back to the Iron Age. Hence it is likely that the marble quarries were found upon procurement of soapstone for vessels and perhaps garnet micaschist for rotary querns. Together with the Allmenningen marble quarry, the Sparbu quarries provided white marble for shafts, pillars, floor and tomb slabs to Nidaros Cathedral – the northernmost of Europe’s great medieval cathedrals. The cathedral is heavily infuenced by English medieval architecture and so is the use of marble. Marble for English cathedrals was provided from the famous Purbeck quarries with traditions back to the Roman Iron Age and beyond, but also from Frosterly and other places. In this paper the Sparbu quarries are compared with the Purbeck quarry landscape and it is argued that they can be viewed as a miniature version of their bigger sister.
life in ancient Egypt."
Forvitringen er utgangspunktet for denne sluttrapporten, som er utarbeidet av Fabrica Kulturminne-tjenester i forskningsprosjektet «Det romanske tårnet til Albanuskirken på Selja: Analyse av inneklima og forvitringsprosesser» (2016-2020). Prosjektet har vært utført sammen med Riksantikvaren og Selje/Stad kommune. Hovedspørsmålet er hvor raskt forvitringen foregår inne i tårnet og hva som er årsakene. Viktige spørsmål er også om forvitringen kan øke som resultat av klimaforandringer og hvilke bevaringsstrategier en på lang sikt kan tenke seg for tårnet.
Rapporten konkluderer med at saltforvitring er den viktigste årsaken til at det faller ned mye forvitret material fra stein og fuger innvendig. Dette er tidligere kun antydet for middelalderbygninger langs Norges ytterkyster, knapt dokumentert. Forvitringen er ikke enkel å observere direkte, men foregår etter alt å dømme som gjentatt krystallisering og oppløsning av salt (natrium¬sulfater, natrium¬karbonater og trolig klorider og gips) når relativ luftfuktighet fluktuerer mellom ca. 60 og 80%, spesielt på våren/forsommeren, men også i andre sesonger. Innvendig murverk har et gjennom¬snittlig tap av tykkelse på 0,5 cm pr. hundre år. Dette kan virke lite, men siden forvitringen er konsentrert til spesifikke områder, kan likevel betydelige bevarings¬utfordringer oppstå i framtiden.
Ut fra tilgjengelige historiske klimadata og prognoser er det sannsynliggjort at fluktuasjoner i relativ luftfuktighet kan øke i intensitet og hyppighet i framtiden. Siden tårnet har mange åpninger og er fullstendig prisgitt værlaget, kan det medføre at saltforvitringen blir mer betydelig. Også nedbørsintensitet og -hyppighet kan øke, noe som kan ha betydning for lekkasjer, biologisk vekst og kjemisk forvitring (av mørtel). Frost vil i fremtiden miste mye av sin betydning på Selja. Klima¬forandringer er imidlertid av underordnet betydning om man sammenholder med direkte menneskelig påvirkning, dvs. i form av manglende vedlikehold på den ene siden – og planmessig, godt vedlikeholdsarbeid på den andre.
Rapporten inneholder en avsluttende diskusjon om mulige bevaringsstrategier, der viktigheten av regelmessig vedlikehold og reparasjon blir understreket. Det blir også påpekt at de store mengdene med «tett», sementbasert murverk og mørtel som ble introdusert under restaureringen i 1912-15 trolig allerede nå gir problemer i form av oppkonsentrering av fukt. På sikt kan dette bli betydelig.
I tillegg til den sterke saltforvitringen, ligger problemene med sement til grunn for diskusjon av de muligheter en har for bevaring av tårnet på lang sikt (hundreårsperspektiv). Siden det er høyst sannsynlig at tårnet var kalkpusset/slemmet i middelalderen, introduserer diskusjonen de positive mulighetene som ligger i fjerning av sement, restaurering med kalkbasert mørtel og – ikke minst – bruk av kalkpuss, slemming og hvitting. Sammen med lukking av åpningene i tårnet (vinduer/ portaler), men med god naturlig ventilasjon, kan et kalkbasert murverk trolig signifikant bedre tilstanden og opprettholde den på svært lang sikt – gitt at det utføres planmessig vedlikehold.
Spørsmålet er hva slags tårn man vil ha: Et monument over restaureringen for hundre år siden? Eller et «levende» middelaldertårn som med autentiske materialer og håndverk peker på middelalderhistorien til tårnet og kloster- og helgenanlegget som helhet?
Experimental application of quarrying techniques supplemented the archaeological data. The quality and properties of the material was assessed trough geological analyses and experimental knapping.
The results show that pioneer groups executed the initial chert extraction during Early Mesolithic (8500-8000 cal BC). Quarrying is also documented during the Late Mesolithic (5000 cal BC). The following 3000 years there is no trace of occupation, but by the last millennium BC the area was again visited.
Intensive activity during resulted in massive amounts of lithic waste spread over a large area. However, there are few remains of dwellings, fireplaces or other structures. We suggest that smaller groups repeatedly and frequently visited the area during the warmer parts of the year, and that the activities more or less exclusively revolved around extraction and processing of chert.
Blocks were detached from the bedrock by using fire in combination with different techniques of pounding and wedging. The chert quality is assessed as relatively low, and we estimate that 70-90% of the extracted material was unsuitable for further knapping purposes.
Informasjon om steinbrudd og bruk er fragmentert og ikke organisert på en måte som bringer denne kunnskapen ut til de som har behov for den. Etter-reformatoriske steinbrudd er dårlig ivaretatt og mange står i stor fare for å bli utilgjengelig/ødelagt for fremtiden. Småskala produksjon av stein, inklusive uttak av restaureringsstein, er gjennom statlig sanksjon og lovverk blitt vanskelig. Det medfører også tap av håndverk og historisk viktige kilder for stein. Lovverk og etablert praksis er lite egnet til å kunne kombinere vern og drift.
Som et resultat av disse forholdene, er vi i Norge i ferd med å «male oss inn i et hjørne» der vi både ødelegger viktige kulturminner og gjør oss ute av stand til å kunne restaurere og konservere byggverk på en god måte i fremtiden. Derfor har vi behov for et strategisk program om stein og steinbrudd, for å løfte kunnskapen, styrke veiledning og forbedre forvaltningspraksis.
Som et av Norges mest sentrale kulturminner har Nidarosdomen influert praktisk talt alle andre bygninger oppført i kleberstein i landet. I dag er Nidarosdomen «eneleverandør» av kleberstein for restaurering av gamle bygninger i Norge – av den enkle grunn at det ikke finnes kommersielle leverandører av kleberstein her i landet lengre. Nidarosdomen driver sin virksomhet på «vrakstein» i et nedlagt, moderne brudd i Målselv i Troms, samtidig som de prøver å åpne en helt ny forekomst i Nordland (Dalhaugen) – på en helt moderne måte og av en kvalitet som definitivt ikke har noe å gjøre med de tradisjonelle klebersteinsbruddene i Trondheimsdistriktet – som ble brukt for å bygge domen i middelalderen. Spørsmålet er om denne virksomheten er autentisk og bærekraftig.
Klebersteinslandet Norge har gått «konkurs». I middelalderen var det bortimot 100 brudd i drift, omkring 1900 var det 30-40. I dag er det ingen. Globaliseringen har ført til at kleberstein nå blir produsert for en billig penge med høyeffektive sagemetoder i store forekomster i Brasil, India og Kina. Ære være dem. Norge kan ikke konkurrere på dette markedet for billig, stor kleberblokk for fasader, baderom og – ikke minst – ovner og peiser.
Men skal restaurering av Norges gamle kleberbygninger være avhengig av import? Skal restaurering være avhengig av hvordan Nidarosdomen velger å produsere stein? Skal ikke steinproduksjon for restaurering ha et element av lokal eller regional, håndverksmessig autentisitet? I middelalderen benyttet man lokal og regional kleberstein landet rundt. Man hogde stein ut av berget med manuelle metoder. Er ikke dette viktig lengre?
I essayet gis det alternativer til import og til avhengigheten av Nidarosdomen. På bakgrunn av historien til produksjon av kleberstein i Ottadistriktet og eksperimentell produksjon av stein i Europa – også ved Nidarosdomen – argumenteres det for at enkle, gamle, «middelalderske» metoder i fremtiden kan utgjøre kjernen i steinproduksjon for restaurering. Mange brudd i Norge peker seg ut for slik produksjon; de blir listet opp i artikkelen.
Å ta i bruk «middelalderske» metoder for å bryte stein i gamle kleberbrudd til restaurering krever imidlertid et tankeskifte: Vi trenger ikke stor blokk, vi trenger ikke industriell virksomhet, vi trenger ikke «lønnsomhet». For dette er kulturminnevern! Det er eksperimentell arkeologi! Det er å etterligne «middelalderske» metoder for uttak av stein som levde i beste velgående helt opp til 1930-tallet i Norge. Ved bruk av slike metoder har man nemlig en mulighet for å ta i bruk steinforekomster som nå ikke peker seg ut som spesielt lønnsomme. Men som var i bruk i tidligere tider.
Og derfor tas det i essayet en avstikker til produksjon av kalkmørtel. Alle vet at industrielt produsert Portlandsement, industrikalk og NHL (importert «naturlig hydraulisk kalk») er høyst problematisk for å restaurere våre steinbygninger. Derfor finnes det nå et vell av initiativer for å produsere god, gammel, lokal «middelalderkalk» – også ved Nidarosdomen. Initiativene er en ubetinget suksess. Det gir grunn til ettertanke også om steinproduksjon på «gammelmåten».
Hovedformålet har vært å legge inn Norges og Nord-Europas største steinbruddslandskap fra viking-tiden og middelalderen på en adekvat, moderne måte i Askeladden, Riksantikvarens nasjonale database over kulturminner. Det dreier seg om et stort, UNESCO-verdensarv¬nominert landskap som strekker seg over nesten 20 km på nordsiden av Sognefjorden fra den gamle gården Myklebust ved dagens Hyllestad sentrum og vestover langs Åfjorden til Eide, på grensen til skjærgården mot Atlanterhavet.
Prosjektet har på bakgrunn av eldre kartlegging, og ny kartlegging foretatt i prosjektet, utført følgende:
1. Utarbeidet lokale GIS-baserte temakart for formidling og forskning.
2. Lagt inn en testdel (Kvernsteinsparken) som lokaliteter og enkeltminner i Askeladden, for kommunal og fylkeskommunal forvaltning.
3. Foreslått forbedringer i hvordan gamle steinbrudd behandles/representeres i Askeladden
4. Lagt inn hele steinbruddslandskapet i Hyllestad som kulturmiljø i Askeladden, for forvaltning.
5. Foreslått temaer til diskusjon når det gjelder definisjon av et stort steinbruddslandskap som kulturmiljlø, bl.a. når det gjelder forholdet til andre kulturminner innenfor landskapet og ikke minst forholdet til kommuneplaner og reuleringsplaner.
I rapporten beskrives arbeidet i detaljert form. Prosjektet kan anses som en case-studie til hjelp for kartlegging av også andre gamle steinbrudd, med tilhørende innleggelse av data i Askeladden.
Totalt er det registrert bort i mot 60 enkeltsteinbrudd, flest på Hovedøya. Det dreier seg stort sett om små brudd som ble benyttet for leveranser av murestein og "gråstein". Det er ingen brudd for "finstein" nær klosteranleggene; stein som ble benyttet til arkitekturdetaljer og skulptur. Slike steintyper (kleber, metaolivinstein, kalkstein, marmor) ble "importert" fra brudd lengre unna anleggene.
Et av målene med undersøkelsene var å kartfeste enkeltbrudd og steinbruddslandskaper, slik at de kan representeres i Askeladden, Riksantikvarens sentrale database over kulturminner i Norge. I rapporten gjøres det rede for vanskelighetene ved kartfesting av slike, til dels store landskaper, og det gis anbefalinger til hvordan vanskelighetene kan overvinnes.
Rapporten har et innledende, teoretisk kapittel der beskaffenhet, registrering og datering av steinbrudd blir diskutert. I et avsluttende kapittel med diskusjon og anbefalinger blir temaer fra innledningen gjenopptatt i lys av undersøkelsene som er foretatt. Det konkluderes med at det foreliggende pilotprosjektet bør videreføres i et hovedprosjekt, med mål om å utarbeide maler eller en liten håndbok for registreringer av alt fra små enkeltsteinbrudd til store steinbruddslandskaper i Norge. Her vil, naturlig nok, resultatene fra pilotprosjektet utgjøre en grunnstamme.
Den viktigste grunnen til at pilotprosjektet bør videreføres, er at få steinbrudd, og spesielt de store og viktige steinbruddslandskapene fra middelalderen og nyere tid, er svært dårlig representert, hvis overhode, i Askeladden. Mange av disse industrikulturminnene har derfor dårlig vern. Om de er kjent, så er dette ofte i lokalmiljøet og i fagkretser, men ikke nødvendigvis hos ansvarlige myndigheter og utbyggere som fort kan få seg en overraskelse når graving pågår og det allerede er for sent.
The thesis begins with a comprehensive introduction to the weathering problems of the cathedral. Part I contains methodology guidelines and a brief summary of current theories of weathering processes related to soluble salts and air pollution. The methodology guidelines highlighting the context-dependent nature of weathering are derived from the work of Andreas Arnold and supplemented by a brief summary of the structural aspects of stone buildings, as well as illustrative case studies of Molasse sandstone, a medieval church in Germany and 3500 year old Egyptian obelisks.
Part II gives an overview of the cathedral’s history, building construction and significant structural problems. Soapstone, greenschist, marble, sandstone, various hard stone and slate from 60 different quarries are briefly described, as are medieval lime mortars and mortars based on Portland cement which were introduced in 1869. Attention is also paid to specific conservation methods used during the restoration. This section ends with a comprehensive overview of Trondheim’s cold temperate maritime climate, the history of air pollution in this relatively “clean” city and the warm and dry indoor climate of the cathedral.
Part III deals with description and interpretation of observed weathering phenomena on the most important types of soapstone and greenschist at the cathedral. Weathering phenomena in eight quarries are presented and compared to the behaviour of the respective stone types at the cathedral and other monuments. The study shows that there are significant differences between soapstone and greenschist used in the Middle Ages and soapstones introduced during the restoration. Such differences are interpreted on the basis of analyses of material properties and experiments. The study also shows that several stone types produce sulphate salts due to their content of iron sulphides.
Part IV contains three case studies of selected large sections of the cathedral; the choir, nave and north transept. These case studies give an overview of their associated weathering problems and explain the findings in terms of building construction, stability problems, materials, exposure conditions and recorded water leaks. The last issue is extremely important.
Part V contains four case studies of selected parts of the cathedral severely affected by salt weathering and one case study of Romanesque corbel heads. The evolution of the salt systems are followed from the original building period to the present. Generally, salt weathering was a minor problem prior to the restoration and it was the introduction of highly alkaline Portland cement as well as gypsum derived from stone and air pollution that greatly increased the salt load. It is also shown that the alteration of roof design in the 1880s can explain the rapid weathering of Romanesque corbel heads.
Part VI summarises and discusses the results obtained and gives comprehensive suggestions for conservation measures. The most urgent problems are: 1) Structural instability occasionally resulting in stonework detaching inside the cathedral; 2) Rapid weathering of certain stone types frequently leading to loss of large pieces from elevated exterior areas; 3) Extremely poor water discharge systems and unsatisfactory insulation of exterior gangways and platforms, giving rise to leaks, salt weathering and unwanted run-off along sensitive stonework; 4) Joint fissures in stone capped towers, gables and large sills, resulting in salt weathering below; 5) Rapid weathering of poorly protected medieval sculpture as well as new sculpture made from stone of poor durability.