I keep a cup of brushes for single colors, for inks, for textured paints(sandstones and SnoFlex) and I keep two plastic cups marked "Art Cup" for both regular and metallics water. I learned the hard way that I had to mark my cups because I am often interrupted by the Mrs. when she hits a pinnacle in her gaming, and more than once I have taken a drink from my art cups without looking carefully.
For my airbrush, I have to keep myself in those glass bottles because I am constantly experimenting with paints and inks to create a truly hardy fleshtone.
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Sometimes, the mad are driven that way.
http://capolan.tripod.com/- Some Stuff.