On Fri, 19 Sep 2008 04:39:04 +0100, Rod
wrote:

If you are thinking lime plaster (and that would be expected!), I don't
know. But for gypsum the temperature is quite low and could easily be
achieved round a wood burner.

Well I suppose I am because I've often seen lime mortar used to line
fireplaces and flues. I just looked up the burn temperature and
900degC is mentioned

Anna

"Gypsum rock is converted into gypsum plaster by driving off some of the
chemically combined water. Heating gypsum at 120°C for one hour results
in a hemi-hydrate (CaSO4.1?2H2O) €“ with three quarters of the water
removed. Gypsum hemi-hydrate is also known as Plaster of Paris.
Prolonged heating over several hours results in the formation of
anhydrite with practically none of the chemically combined water left."

http://practicalaction.org/practicalanswers/product_info.php?products_id=305

--
Rod

Hypothyroidism is a seriously debilitating condition with an insidious
onset.
Although common it frequently goes undiagnosed.
www.thyromind.info www.thyroiduk.org www.altsupportthyroid.org

--
Anna Kettle
Lime plaster repair and conservation
Freehand modelling in lime: overmantels, pargeting etc
Tel: ***(+44) *01359 230642
Mob: *(+44) *07976 649862
Please look at my website for examples of my work at:
www.kettlenet.co.uk *