MITRA Forum Question Details

I am not a huge fan of hardboards but that is because of how fragile the corners can be and the huge difficulty of getting an expanded crushed corner back into something resembling planarity.

Beyond this, your plans seem reasonable. The fatty acids in the oil should not cause any deterioration of the panel without a size.

Concerns about paintings oil over acrylic dispersions paints (grounds or paints proper) were vastly overstated in the past. Oil over acrylic dispersion grounds have shown to be quite stable as long as the surface has some rigidity (multiple layers of a high-quality acrylic dispersion ground on canvas or on panel with or without a ground).

​(*Edit: I see this was mentioned in the previous question. Sorry! I will leave my comment as a response.)

One concern I would like to raise is the "thirstiness" of bare hardboard. This support material can wick away a lot of oil from the paint in the first layers, so even if the artist is avoiding water-borne sizings to prevent swelling the board, it may be a good idea to treat the panel in some way to reduce absorbency (alkyd medium?)

There are a couple of different things going on. Degreasing is mostly recommended to remove any oil (including hand oils) that may interfere with the adherence of an aqueous size or ground (glue, acrylic dispersion, etc.). It wouldn’t hurt to do so if you are applying an oil ground, but it would not be as important.

It would, of course, be preferable to seal the panel. That was not part of the original question. Whether a tempered hardboard would absorb too much oil if the paint was painted directly on the surface, I would need to test. Put a drop of linseed oil on a panel and observe if it spreads into the panel. As I originally wrote, I am not overly fond of hardboards as substrates for other reasons and I do not have any around at the moment to check, but I seem to remember them being rather slick and the surface quite closed. That is one of the reasons when in the distant past I used them, I would always sand the surface so that there was some mechanical tooth for the ground to hold onto. However, Matthew seems to have more experience with the material, and I will defer to his judgement.

So you could seal the panel and paint on the sealant layer, you could apply an alkyd ground (the alkyd ground is going to be ready for paint well before a more traditional linseed oil bound ground but the later would work as well) over the sealant, or you could apply an water-borne ground over an appropriate sealant like described. I would also make a small test panel and paint some oil paint directly on the panel. Let it dry for a while and check for adhesion.

​Right, my word of caution was not in reference to any destructive effect that the oil might have on the panel material, but rather because I have observed oil paint on bare hardboard leaving a pronounced oil stain and colors becoming dull and waxy as a result of the oil being taken up. I don't know whether this is enough to diminish film strength.

​Acrylic mediums with low viscosity may sink into the panel more than a more viscous medium, so it may be that "gloss medium" was observed to yield a heavier film. That is just a guess.

Artists who eschew water-borne sizings and primers for hardboard may do so because water can swell fibers and raise an undesirable texture. Alkyd mediums and oil-based primers do not produce this effect. Where working properties are concerned, oil primer yields what is considered a "fast" ground, in terms of brush movement, compared to "slow" acrylic grounds which, being more absorbent, cause a little bit of dragging and "break" in brush strokes. There are ways to overcome this and improve lubrication in the first applications on an acrylic priming, by rubbing in a small amount of medium to reduce absorbency.