Calcium Sulfate / Gypsum

 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

 mj wrote:

Plaster of Paris.  You'll probably have to hydrate it to make it useful.

Bob

 
As in every elementary school  project plaster of Paris?  I need it in
a dry form mixed with all the other stuff and then it is dissolved
into the water system.

 mj wrote:

Yes.  But you want hydrated calcium sulfate, CaSO4·2(H20), and Plaster
of Paris has been dehydrated to 2(CaSO4)·H2O.  So you'll probably want
to add excess water, let it harden, then pulverize it.

Bob

 
I failed chemistry, why harden it first, because just adding it to the
water in the system it will harden there? Thanks for all the help