Black Cloud Away?

[spareparts]

my father messed around with home built aircraft, he helped his brother start a project building an ultralight(never finished due to my uncles death from cancer). One thing I took note of, was everything they opened a new bottle of any type of adhesive or resin, they would make a test piece and check it to make sure it cured properly. No I don't do that as often as i should, but I usually start with a small repair or area before i jump into a larger area, just in case.