"Andy" wrote in message
...
Take a look at
http://www.buildingconservation.com

most will think that you just want some builders lime (hydrated lime) added to
ordinay gypsum stuff - this is not what you want.

Maybe I'm wrong, but can't you use Hydrated Lime to make the lime putty? It
would work out a lot cheaper probably. I seem to remember at college years ago
learning about slaking pits and lime putty mixers

Peter