Watercolor & gouache
Gouache vs watercolor: what actually changes on the page
Gouache vs watercolor compared at the brush: light and transparency, working order, corrections, paper, drying shifts and when to combine them.

Transparent washes, opaque color and the habits that keep a painting fresh.
Gouache vs watercolor compared at the brush: light and transparency, working order, corrections, paper, drying shifts and when to combine them.
Gouache is opaque watercolor: the same gum arabic binder, more pigment and often a white filler. Here is what that means once it touches paper.