On Mon, 19 May 2008 00:05:02 +0100, Alan wrote:

These people sell it: http://www.organiccatalog.com/catalog/. 12kg
for 19.95 GBP, 3kg for 5.55 GBP. Just put "gypsum" in their search box
to get toit.

http://www.wickes.co.uk/invt/220058
£4.35 for 25Kg from British Gypsum.

(17p per Kg)

Beat me to it, I was going say about a fiver for a 25kg bag of plaster.
You may even be able to get it cheaper as it doesn't keep and has fairly
short shelf life when it comes to spreading it on walls. Old plaster sets
too quickly and doesn't have long enough "plastic" stage to allow for
polishing.

Not all building plasters are equal, I suspect a finish plaster rather
than bonding, base, or multi purpose would have a higher gypsum content.

--
Cheers
Dave.