If I want to mix gouache with acrylic, what special concerns do I have?

Question

Are there any techniques to use or any issues with preservation and separation? Also, what is a better diluter for acrylic than water? I have been using a matte glossing agent.

Answer 1

Since Gouache is water-resoluble, you'll want to mix it with a polymer emulsion medium or gel, either matte or gloss, with no water at all.

With either gouache or acrylic, gloss medium will give you better colour saturation, since matte has miniscule particles of silica in it - which will make the paint appear as though you're looking through frosted glass. Use too much, and it dulls the colours down. You can always finish with a matte varnish.

When using acrylics only, use as little water as possible. Water tends to break apart the binders that disperse the pigments, leaving a streaky finish and causing adhesion problems.

Painting gouache over acrylic or vise versa will not work - the binders, though not incompatible, just aren't the same. You'll have serious adhesion problems (cracking and peeling) within a short period of time.

But did you know you can buy Acrylic Gouache? Holbein makes it, and it's absolutely delicious, matte finish and non-resoluble. Looks like all the online dealers sell it.

http://www.holbeinhk.com/acrlgoua.htm

Answer 2

I'm not sure if you are asking about mixing wet gouache & acrylic or if you mean using the 2 types of paint on the same canvas... They'll separate if you use acrylic & gouache together while wet. On the same canvas, or gouache over dry acrylic is fine with no real issues.
As for diluting acrylic, matte/ gloss mediums are what I've used.