Because I seldom use my b&w chemicals, I mix only about a quart at a time, and even then routinely have them go bad before I use them again, and then have to mix a new batch. Very annoying. I had hoped to buy some cheap dark-glass bottles and then use one of those wine-bottle vaccuum devices and rubber stoppers to pump out the air. The problem is that I can't find the bottles anywhere. I know that I can use actual wine bottles, but they aren't quite large enough, I don't think. And I've tried those collapsible plastic bottles but they tend to spill and will eventually crack, I think. Suggestions welcome.