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I am making panels for oil painting only--no other media. I begin with masonite which I lightly scuff and then apply two coats of GAC 100, then two coats of Acrylic Gesso and finally a few coats of Sandable Acrylic Gesso. My goal is to achieve a smooth surface and I'm pleased with my initial results.
I do have a few questions that I hope you can answer:
-- For oil painting only, should I still first use GAC 100 or can I start right off with Acrylic Gesso?
-- If I should use GAC 100, would GAC 500 work just as well. (I am interested in the self-leveling property.)
-- Do I need to use Acrylic Gesso before applying Sandable Acrylic Gesso? I seem to remember reading that in one of Golden's guidelines for use but cannot now locate it. From what I can find I do not need to use regular gesso before applying sandable gesso.
-- Can I tone Sandable Acrylic Gesso with dry pigments? I have toned the Sandable Acrylic Gesso with a raw umber aquaeous dispersion from Natural Pigments and that seemed to work well. I later read that Golden recommends toning with acrylic paint. I'd like to be able to use my collection of dry pigments if that is possible.
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And here is Golden's reply:
We are not fans of hardboards, generally speaking. 'Hardboard' is the general term for what used to be called masonite, which was a brand of hardboard, not produced anymore, to my knowledge. Hardboards are made with wood dust and a variety of ways of getting them to stick together. Some use resins, some use polymerized oils, etc. The main issue has to do with moisture sensitivity. We think that either Birch Plywood or MDO Plywood are better choices, and that either of those panels would have better dimensional stability. Having said that, many artists are still using hardboards of various sorts. It is possible that certain types are more stable than others, but we do not have that information.
You do not need to be concerned with SID or support induced discoloration if you are painting with oils, so the GAC 100 or another stain blocking primer is not required for that reason. The other reason for using GAC 100 is to block oil absorption into canvas, but I doubt this is a concern with the hardboard. We still like the idea of some kind of separation or primer, and you could use a commercially available one such as Kilz, in either the alkyd or water borne variety, or you could use GAC 100. The newly re-formulated SHG does not require a coat of Gesso first, so you can apply it directly over the GAC 100 ( or 500 if you like, in this instance ), or commercial stain blocking primer.
Yes, assuming you can get the dry pigments to disperse well, you can use small amounts to tint the SHG. Too much may make the mixture have a higher propensity to crack or craze upon drying. The reason we recommend acrylic paints is because dry pigments tend to clump and it is difficult to get then dispersed and homogenized in the material, without using a paint mill or special mixing machine. But, if you feel it is working for you, then by all means go ahead.
Our Sandable Hard Gesso tech sheet is found when you put your cursor over 'Products", then click on 'Gessos and Grounds'. Here it is:
I hope this information is helpful, and if you have more questions, please don't hesitate to call or email.
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My follow-up responses:
I finally found the reference to first applying regular gesso before sandable--right on the label. So for now I'll stay with my process until I pick up a new jar of sandable gesso.
I hear you on the dry pigments. I suppose I could try to premix pigment with gesso using a palette knife or muller on my grinding glass but I'd be going against the quick drying nature of the gesso. All this instead of a little squeeze of acrylic paint...
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I'll be documenting my adjusted panel making in a later post. I have plywood to cut and a proper color of acrylic paint to select. I've learned that even with an established process, it must be revisited to keep up with product changes.