“I have a question regarding acrylic paint in tubes. When the lid breaks, as it so often does on a new tube, is it okay to keep the paint in a small glass jar and should I add water to it to keep it from going solid.” — Lyn
Yes, and if the lid is airtight you shouldn’t have to add water to it. You’ll easily tell if it’s drying though, and then a little water does the trick, just don’t leave it for weeks before you check! If in doubt, put a piece of clingfilm over the top before screwing on the lid for a tighter seal.
It’s worth saving caps from used-up tubes as spares (in wherever you put your tubes, not in a never-to-be-found-again safe place). Also check the size of other things with caps, starting with your toothpaste, as often while the cap itself is bigger overall than a paint tube’s but the screw thread is the same size.
If you’re in a hurry, invert the tube in a container with a little water, enough to cover the broken cap.