This has been asked time and time again, but I wonder if Gypsum from the garden section of your hardware store is really all that different. The guaranteed analysis of Gypsum on the 30# bag says 92% gypsum, 8% Calcium, Sodium, and inert materials. To a novice, this seems pretty... gypsummy. Does food-grade Gypsum found in Asian markets promise an even better guaranteed analysis, or should hop heads everywhere head to their favorite tool shop and nab a 30# sack of lawn gypsum? Is local homebrew store gypsum the biggest conspiracy to brewing since Belgians saying light candi syrup is really all that different than table sugar? Is putting stuff bound for the lawn in my beer going to kill me?!
Thoughts? Because 20$ for a lifetime supply of Gypsum seems like quite a bargain.