Cracking when painted too thickly
“My thick gouache paint cracked and flaked off the paper like dried mud.”
What is happening
Heavy impasto marks or thick layers develop hairline fissures and begin to chip away from the surface. The dried paint loses its adhesion and flakes off if the paper bends.
Gouache lacks the flexible polymers found in acrylics or the durable film of oil paint. It relies on brittle gum arabic, which cannot bridge thick deposits without cracking under internal tension.
The 30-second test
Gently flex the corner of your paper or touch the thickest ridge with a fingernail; if flakes break loose, the paint is too thick.
How to fix it
- Carefully brush away loose, loose flakes into a bin without scratching the paper.
- Dampen a soft flat brush with clean water and smooth down the fractured edges.
- Mix fresh paint to the consistency of melted ice cream rather than paste.
- Reapply the colour in two thin, uniform coats rather than one heavy impasto stroke.
Can it be saved? Partly
Scrape loose flakes gently, reactivate the remaining paint with a damp brush, and re-lay the passage in thinner coats.
Drill: Consistency control ladder
About 15 minutes. You need:
- Gouache
- Water dropper
- Watercolour paper
- Round brush
Mix gouache at butter, cream, and milk consistencies. Paint swatches of each and note which hold flexible adhesion once dry.
Background reading
General teaching sites on this subject. They are a reading list, not page-level citations for this advice.
The advice is a generated synthesis of common teaching practice and has not been checked line by line against any source; treat times and difficulty as estimates.