The problem is that while the alternative to dye-that is, pigment-does not dissolve in water, it does something else in liquid that is also problematic: It takes the form of suspended particles.
只是，顏料不溶於水，在水中呈現顆粒懸浮狀，若顆粒太粗重，會有沈澱現象，不能均勻地分佈。