I’ve read when using aniline dyes that you should mix only what you need. What is the reason for this? I store the leftover dye in airtight jars and, so far, I haven’t noticed any problems. Is there something I’m missing?
Michael Dresdner: Dyes mixed in water can grow mold and bacteria, which can both smell bad and alter the color of the dye. This is not the case with dyes mixed in lacquer solvents or alcohol, both of which kill such organisms. Adding a bit of alcohol to a water-soluble dye mixture helps considerably. Any dye left in sunlight can fade, whether it is on the wood or still in the jar, so do store dye away from light.