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Forum URL: http://www.truefresco.com/cgidir/dcforum/dcboard.cgi
Forum Name: Plaster Arts & Modern Plasters and Classic Finishes with Joe Greco
Topic ID: 19
Message ID: 9
#9, RE: Traditional and Modern lime plasters
Posted by Gary sculptari on 17-Apr-05 at 06:54 AM
In response to message #7
I also replied elsewhere on the forum.

I just wanted to add that I have been experimenting with magnesium cements - and they much harder than even 100 year old lime. The only problem with the magnesium content is that it can create hard patches in lime plaster - which ONLY creates a problem when the wall is shrinking and contracting (frost and water) and only when magnesium levels are high enough to create this problem (I think 15% has been suggested somewhere). The magnesium is a non-issue - you would have difficulty finding a lime with high magnesium, maybe some agricultural blend (magnesium is wonderful for soil, especially grazing pastures). Efflorescence is not caused by magnesium.

So we are dealing with Calcium Hydroxide - and how, and where, and for what purpose it was calcined becomes the only issue. I was suprised the Graylime was sandy - they add the sand for you?

Check out some of old plaster books at donhead.com if you really want to learn about lime, and lime mortars.