Does alum for picking expire?
Kept cool and dry, it will last years and years, it doesn't spoil, but it can get all caked up which renders it useless.
I don't think so. As long as it is kept dry.
According to sources, alum for picking does expire. Alum is a salt compound for shrinking tissues, acting as a preservative, and helping to firm and crisp pickles. Alum is also used in purification of drinking water in industries.