The most important test is probably checking the platelet structure of the aluminium powder, i.e. shape and particle size, and the stabilizer deposited on the particle surface, e.g. stearic, oleic and other mono and polycarboxylic acids. To do this, one must first separate the pigment from the paste by careful thinning, filtration or centrifuging.
To determine the yield and hiding power one makes use of the spreading index on water. For this one places a specified amount of pigment or pigment paste on to the surface of the water and compresses it two-dimensionally, using suitable barriers. A continuous film is thus formed, whose extension can easily be determined.
This does not cover pigment particles which have been coated with a hydrophilic substance, i.e. "non-leafing" pigments, which can thus be determined indirectly.