How this category and topics work

This is basically a knowledge base or ‘solution’ type forum category. So lets say you are not sure about the best practice for painting with a particular airbrush, you can post your question in this forum and then once the answers come in you (or moderators) can choose the answer that best works for your situation.

So I will ask a question and see which reply works for my situation.

Question: I have some older paint that ‘seems’ okay. Is there a good way to test it and make sure it is, before using it on my project?