Chris Hogg wrote:
On Tue, 20 May 2008 18:16:28 +0100, stuart noble
wrote:

Chris Hogg wrote:
On Tue, 20 May 2008 17:56:21 +0100, stuart noble
wrote:

Bob Hobden wrote:
"Bob Hobden" wrote
"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.
They said they supply Jewsons and Travis Perkins with this product. The 3
local Jewsons had no idea what I was talking about and didn't have any, the
local Travis Perkins were very helpful and found out they can order it in
but in pallet loads then it's £15 to split a pallet + £40 carriage
+.........

I then tried once again phoning Farm Supplies firms locally and also got
nowhere. Hope you have better luck!

Would gypsum be any different to garden lime for this application given
that both are alkaline?
In terms of their effect on clay, no real difference. Lime may even be
more effective. But lime will raise the alkalinity (pH) of the soil,
which you may not wish to do, although if the gypsum is from flue gas
desulphurisation in coal-fired power stations, as much is, it may well
also be alkaline from residual unconverted lime.

According to the product description, Gyproc agricultural gypsum is
alkaline. Given how difficult it seems to be to find a supplier, is
there any point?

Any point in what? Using gypsum instead of lime? Probably not, if
you're not worried about the alkalinity, but if you're on acid clay
and want to grow lime-haters, you would want to use mineral gypsum.
Whether you can find it is another matter.


Isn't mineral gypsum alkaline as well?