ijustwanttopaint wrote:

Thank you for your reply. I feel a bit relief. I can show you exactly how the boards look here. I guess its good quality. But its not coated on both sides. How does the backside look? Is it good quality?  If you cant lean them at the wall is it okay to stack them flat on top of each other? Or will the paint/varnish be damaged? What marerial can you use between the boards if you want to stack them? Plastic? Textile? Cardboard? Will the surface suffocate if you do this? I mean if they have to be able to breathe even if they are varnished. How long can you wait in before you should do cradling or framing? If they warp can you bend them back by stacking books on top if you cover the surface with materials mention above?

That looks like pretty poor quality hardboard.  Is it blackish on the surface?  Who knows what’s it made out of and what’s been applied to the surface.

Like Eon says it should look like Ampersand panels – warm brown and smooth on each side.  Before Masonite stopped making hardboard, their best variety was call “Duron”.  There are still companies making Duron-type hardboards (using heat and pressure and only the adhesives found naturally in wood).  It’s often referred to as Duron, even though it’s not by made by the Masonite Corporation.  It’s frequently used by cabinet makers for the backs of certain types of furniture like dressers and nightstands.  Google Duron Hardboard and you’ll learn more about it.  At the top of Google’s search page click the Images tab for photos.

You need to cradle hardboard panels before you apply gesso.  It needn’t be elaborate:

Go to the lumber yard and get this size clear pine strips

Be sure to check them before purchase by putting one end on the floor and other end up near your eye (not too close in case someone runs into you with a cart) and look down the strip for any bowing or twisting both on the face and on the side.  This is important.  Sometimes there’ll only be a few that aren’t warped.  Whenever I go to Home Depot, I’ll check for these pine strips and buy a couple.  I store them upright at an angle in my studio and they don’t seem to warp, even after years.   I’ve used this size on 1/4″ thick panels up to 48″x48″ without any warping for 30 years or so.  I only use the 1/4″ hardboard for all sizes.  I don’t think the 1/8″ should be cradled; it’s too flimsy,  it might visibly bulge inwards or outwards while the part glued to the 1-1/2″ pine strip remains flat.

You’ll need tools.  Jig saw, orbital sander and miter saw.  You’ll also need clamps.  4 corner clamps and at least 16 to 20 C-clamps (two per corner join and the rest for in-between).  And little square pieces of hardboard to put between the surface of all the clamp jaws and the face and back of your panel so they won’t get marked.

The cradling or framing needn’t be elaborate.  Strips just around the edges are fine up to 48″x48″.  Beyond that you may have to have some cross-bracing in there, but you won’t want to glue those to the  panel.  Below is the cradling on a 20″x20″ panel

Trim the hardboard to the correct size.  Before gluing on the pine strips, give the hardboard a sanding on both sides.  Dust it off and use denatured alcohol on a clean rag to remove the remaining dust.

Miter the ends of the pine strips so they’re joinable.  Make sure the two strips for each opposing side are exactly the same length.  Apply wood glue to the mitered ends and join in the corner clamps.  The next day check the flatness of the frame and align the frame and hardboard panel to confirm that they’re both the same size and joinable.  Apply a bead of wood glue along the middle of underside of the frame and then take an old credit card or one of those plastic squeegees, meant for fiberglass, and smear the glue so it evenly covers the underside of the pine frame.  Align it with the hardboard which should be face down on a table.  Then attach the C-clamps – one on each side of the corner joins and the rest evenly in between.  Be sure that you put the little scraps of hardboard between the clamps and both sides of you panel.  Wipe off with a slightly damp cloth any glue that oozes out along the inside or outside. Let dry overnight.  Remove all the clamps and wipe off the face again with denatured alcohol.

Now apply masking tape along the edges of the pine strips, an 1/8″ or so below the glue line.  You’ll be covering the glue line with the acrylic gesso.  This will neaten and protect the dent-able edges of the hardboard.  It’s a good idea to extend the masking tape around to cover the back of the pine strips.  Gesso-ing is messy and if you’re applying varnish (instead of paint) to the  back it’ll keep things looking neat.

Apply the acrylic gesso – 5 or 6 layers.  Apply each gesso coat so the brush strokes are going the opposite direction of the previous layer.  Allow them to dry enough that the new coat won’t pull up the previous layer.  Depending on the weather and the humidity maybe an hour between coats, maybe more.  As you finish each coat be sure to apply a thin layer each time around the masked off edges, using upward and sideward strokes.

After all the coats of gesso are dry and they’ve cured for several days (maybe more) you can gradually smooth the finish with an orbital sander and a particulate mask (on you).  As I mentioned earlier, be sure to get a fine (220 grit) non-stick sandpaper.  It’s treated with Zinc Stearate so the acrylic gesso doesn’t gum up the surface of the sandpaper.  It’s also called “non clogging” or “no blocking” sandpaper.  The finished surface will be smooth and matte.  Quite a bit smoother than Ampersand’s Gessoboard.  Here’s a side-lit closeup of the surface. The pink streaks are from the watery thin imprimatura, they aren’t in the gesso itself.

It’s a good idea to paint the pine strips and the back of the hardboard with exterior spar varnish or that brush-on white epoxy appliance paint is also good (its hard and resists dents and scuffs).  You want to isolate the unfinished wood on the back of the panel from warping due to moisture.

Per your last question:  You can’t stack oil paintings on hardboard;  they’ll stick and the paint can deform.  Too much weight and the oil paints continue to out-gas as they age.  They might even self combust.

ijustwanttopaint wrote:

Thank you both for your feedback its very valuable to me. The blackish surface is some heated organic oil to protect the surface from water and moist. Board is used for sub-flooring in houses etc. Im confused now but im gonna look into some other alternative if you say its poor quality. How about these then? I have a hard time finding exactly what you’ve shown. Limited retail here I guess. But this is oil-hardened masonite, photo taken from their site. They come as 120x240cm for roughly 20 dollars, 3 milimeter thick. I don’t know how the backside look though but i guess they are the same on each side? What do you think? I just want to find the best board I can get around here and just stick with it… the earlier i find it the better.

There’d be no reason for the surface of the board to be blackish unless it was burnt.  You don’t want a burnt board to paint on.

That site’s image is not a photo it’s a computer generated rendering with a synthetic texture added and a bump map.  I don’t know what their trying to  show here – it looks like corduroy fabric on the surface.

$20 for a piece that’s 3.94 x 7.87 feet (120 x 240 cm) is kind of low for a quality hardboard here in US it would closer to $40 – $50 – but I don’t know where in the world you’re located.

Looking closer at your post 3 millimeters is too thin – that’s 1/8″.  6 millimeters is what you want.  So maybe $20 for that size is about right.  But again 3 millimeters is too thin.  Breaks and warps too easily. And what’s with that texture?

Oil doesn’t harden anything.  It’s soft and rubbery when freshly dried and becomes shriveled and brittle when old.  You shouldn’t be shopping for a building material used for sub-flooring – that’s just using forestry waste products and fillers.  You need to look for a product that’s made to be seen, not buried under plaster and/or siding.  Look at this ad it specifically says what the hardboard is used for.  Email the company and ask specifically if its suitable for cabinets, store fixtures and displays – if it’s a Masonite Duron-type hardboard product (and if it has a smooth surface on both sides).

What country are you in?  You aren’t anywhere near a large city that would have lumber suppliers that cater to furniture and cabinet makers?  You don’t need building materials to frame a house.  You want materials that a hand-worker in wood uses.

Let’s face it buildings are built by companies that submit the lowest bid.  And building codes require that between layer A and layer C there has to a layer B that fulfills a buffering, isolating or insulating function.  It doesn’t matter if it’s high quality, it isn’t load bearing and as long as it meets the building codes that’s how the builder saves some money.  That’s where that “hardboard” you bought comes in.  The contractor isn’t using first-grade clear lumber to frame a house; he’s using wood that’s full of knots, stains, irregularities etc.

Do you have a sign makers supply somewhere around?  Dibond type aluminum composite panels are thin durable unaffected by moisture and relatively easy to cut.

Painting on Dibond

I agree with Antonin, I think ACM Panels (Dibond is one trade name) are the way to go. They are also easy to prep.