I buy mine from Artcraftchemicals. While it is possible to make your own, at some point you will have some pretty concentrated acid, either as a by product or an ingredient. Even as a chemist I dont want to have that stuff in my DR. If you absolutely have to make your own, look at Perez's site, he has a pretty good method. If you figure the cost of buying the raw materials, the time spent doing it and the possible hazards, buying it in powder form is way more efficient and safer.