#4, RE: Magnesite Marble & Terracotta
Posted by bobby tucker on 25-Apr-06 at 07:00 PM
In response to message #0
>I thought it would be interesting to pass on >some of why findings regarding magnesium >oxychloride cement, patented in 1800's as >Sorel's cement. It is important because it may >easily be mistaken as scagliola or stucco - but >is an entirely different material chemically. It >is interesting that it is a totally natural >cement, based on dried up ancient oceans for its >two components > >The modern variation is 10,000 to 12,000 psi >compressive strength - thats up around Moh 2 on >another scale - like grantite - no gypsums or >cements can approach that level without a lot of >special modifications. Plain portland cement is >about 2,000 psi. > >It is completely fireproof - up to 2300 degrees >fahrenheit and can withstand a tensile shock. It >is simply the very best flooring and wall >material available. It resists both acids and >solvents. > >Here is a link explaining some of its historic >use in the los angeles area: >http://homeandhearth.keenesentinel.com/design.htm#2 > >Restorers should also be aware that early >practitioners added cheap, asbestos fiber as a >bulking filler. Another filler is wood flour, >because unlike lime or cement, this material is >not alkaline and can use organic fillers - like >wood, straw or hemp. It shrinks very slightly, >so a lot of hard sand filler is not needed. It >cures in four hours and does not require >continuous wet. > >It has fallen out of favour because it is >expensive compared to standard concrete and >gypsum. But there is simply no substitute for >scultped and or highly polished finishes.
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