mj wrote:
Where can I buy a pound or two of this and not have the shipping be
crazy? Where could I buy it in say a local store? I have all the other
chemicals for my hydroponics except this one and I don't want to have
to buy a ton.

MJ

Please consider that this is an international forum. How is anybody going
to answer your question as asked without knowing where you are?

You might also consider how pure the calcium sulphate needs to be. The
stuff sold for agricultural use often has small amounts of heavy metals in
it. I am not sure what the consequences of that would be in hydroponics.
You will pay much more per kilo for purified stuff than standard.

Thirdly consider why you are adding calcium sulphate. Is it to provide
mineral calcium or sulphur? There are some obvious substitutes for
providing calcium possibly some for sulphur if given some thought. There
may be side effects of substitution so if you don't follow the chemistry
involved you will have to stick to the formula you have been given.

David