"STB is lazy and requires dangerous amounts of sodium hydroxide (usually drain cleaner grade so who knows what metal impurities are in there - and maybe in your spice). I would be much much more worried about that than buying acid or heating in a pot. With a proper acid/base extraction your result is much cleaner and swim hopes people here value their health. Shortcuts aren't worth your health."

STB is a perfectly fine method for extraction. STB and A/B teks both end with a basic mixture that needs to be handled with care. As far as the purity, either method produces a product that can be enjoyed without re-crystalization if done properly, but both benefit from it.