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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: 33
Message ID: 4
#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.