Brian,
repeat after me, "DON'T buy the formularly amidol package". The results don't look nearly as good as Michael A. Smith's formula. I almost gave up on azo before using the Smith formula. there is no comparison!

as pointed out Mike Jacobson at artcraft is the place to get it. I didn't have a scale so he even mixed the formula for in packets for me, at a very reasonable price.
Tom