"Dave Liquorice" wrote
, stuart noble wrote:

Unlike plaster, I don't think gypsum sets when mixed with water. Kind of
important for this application I would have thought :-)

Well building plaster is (more or less) just gypsum that has been heated
to about 150C, this drives off the water from the calcium sulfate
dihydrate to form calcium sulfate hemihydrate.

2 CaSO4 4H2O 2 CaSO4 H2O + 3 H2O (released as steam).

http://en.wikipedia.org/wiki/Gypsum
http://en.wikipedia.org/wiki/Plaster

So the gypsum is already "set". B-)


I sent a mail to British Gypsum and they have replied so...

"Agricultural gypsum is available from our subsidiary company, BPB Formula.
Please contact their Customer Services on 01636 670249 for further
guidance."

I will contact them tomorrow and let you all know where and how much,
meanwhile this is their information...
http://www.bpbformula.com/PDF/EN/Agr...um-English.pdf

interesting it comes in 25kg, 40kg and 50kg sacks.
--
Regards
Bob Hobden