I'm Dutchy, which means I don't throw away anything I might be able to use.  In this context, that means that I clean and recycle paint jars, like old Model Master and Tamiya paint jars.  I like the Tamiya jars the best, because of the inner seal cap that they included.  They're great for mixing paints, and storing paints and solutions for my traveling kit.  I also use them for storing dry materials, like ground pastel chalks.