Originally Posted by scott hill
What is meant by fugitive colors and pigment load ?
Fugitive would be pigment colors that will fade in a relatively short period of time, i.e. have poor lightfast quality. Madder lake is the most notorious of these. Most dyes also have this trait, but there are fast dyes too.
Pigment load is the ratio of pigment to binder. Watercolors can have a high pigment load also, and can in fact be quite opaque. Watercolor pigment tends to be mulled to a smaller size than gouache so that it will flow in water better. A larger particle size of pigment helps gouache achieve opacity and be applied more thickly.
There's no particular rule book that manufacturers follow that differentiates the two mediums. The binder might not even be gum arabic, but glycol. Dextrin is also used in gouache to help make the paint more creamy.