If your paints are made by a respected manufacturer they should be properly marked and contain information on its transparency.
Paints can be transparent, semi-transparent or opaque. Usually they are marked as following:
- White square – transparent
- A square divided into white and black sections – semi-transparent
- Black square – opaque
Transparency level indicates how paints cover your canvas/paper/board, but says nothing about paint quality. These signs show you what to expect from mixing colours and what techniques you can use more successfully. For example, for glazing techniques transparent colours work better while for general painting opaque colours provide better coverage.