Hi,
i see some manufacture selling non-absorbent acrylic gesso for oil painting, the idea behind it is to overcome sink in with regular absorbent acrylic gesso. it maybe good for direct painting style, however i have few questions:
1, the adhesion between oil and acrylic is mechanical interlocking mechanism, if acrylic sucks oil into them, it means the surface area for adhesion is increase like 3D compared with if acrylic not absorb oil that adhesion is only at surface like 2D. so does this mean the adhesion of non-absorbent acrylic gesso is weaker?
2, with absorbent gesso, if painting in layer, because it sucks oil into ground, it systematically fat over lean as the lower layer gives oil so it becomes leaner once applied. however if it is not absorbent, then the layer will not gives its oil, so it may becomes more critical to judge oil content of each tube? which is very difficult.
hope to see your comments!
Hello there,
It depends a little on how you paint, meaning what kind of mediums or added solvents, oil and resins you add to your oil colours as you paint.
If you tend to do ground washes with lots of solvent and oil like you would do watercolour washes on paper, then sure the absorbancy or non absorbancy of your gesso will make all the difference in result.
If you paint in less extreme technique than that, you shouldn’t worry too much about either aspects.
I’m honestly not sure what’s the point of a non-absorbent gesso (or what’s the difference with a gloss medium) but if you mix regular acrylics with your normal gesso you can also make the porosity vary at will.
1 – Yes, mechanically if it’s smoother it has less ‘tooth’ and therefore less adherence. Oil colours are not epoxy glues.
But they do have some stick-to-it-iveness still chemically, so unless your smooth gesso means raincoat-slippery-smooth smooth, oil will still stick reasonnably. Not the best but not as bad as if you were painting on a plastic wrapp. You can start mixing some alkyd to increase the chemical adherence possibly. Or sand your surface a little.
2 – Yes, but also not that much of an issue in itself. Fat over lean is mainly about avoid rigid over flexible that would cause cracking. That generally translates as ‘fat over lean’ or slower drying over faster drying. So long you give plenty of time to your layers to dry and keep increasing the amount of oil to solvent ratio in your layers to be double-sure, you’re following the rule, no matter where you start or what’s in your tube.
Easiest way to go if you’re working on a few layers is to keep your painting mediums ready in order. Ground medium with perhaps 90% solvent 10% drying oil and 1 week to dry. 1st layer medium with 80% and 20% and 2 weeks to dry, 2nd layer with 70% to 30% and 3 weeks to dry.
If you end with pure oil as medium, you’ll need to paint rather thin layers and give them a few month to dry.
Cheers,
Lussh
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