No, it doesn't have to be lab grade. Here is the recipe from Eric Nielsen on the alt list, which is the one I use:
2 lbs of Pot Carb with 1.75 lbs to make 1 gallon of water. 1 lbs = 457
g and 1 gallon = 3.8 l ( top of my head but close enough as it is just POT
Mix your Pot Card into cool distilled water; about 1/2 your total volume.
SLOWLY add your Ox Acid as it WILL BUBBLE!!!!. Add to completion and top
off with water to make final volume.
Do this outside. It releases a lot of carbon dioxide. Not poisonous, but can displace all that nice oxygen filled air your lungs desire.
Originally Posted by eggshell
That does it! Thanks again Clay.