Posted 03 December 2012 - 10:28 PM
What temprature does Copper sulfate flux at? I'm trying to figure out what colorants to put in a saggar, and I'm weighing the pros and cons of miracle grow.
Raku, Pit fired, Majolica, and Stoneware ceramic artisit
Posted 04 December 2012 - 04:21 AM
Its complicated, and miracle grow has way more than one thing in it. Why not just give it a try? I've heard of lots of people using Miracle grow in saggars and pit firings.
Whistling Fish Pottery
Posted 04 December 2012 - 08:01 AM
The range at which some fluxing action (lowering of the melting point of silica) starts is quite low.... well into the earthenware range. But that information is derived from experiential learning for me.... not really formal lab testing. I've never seen a phase equilibrium diagram done on a CuO - SiO2 - Al2O3 system........... so don't know the actual eutectics layout for this particular system.
As a colorant for saggar (or any other type of ) firing when put onto the surface of a piece, it "steals" some of the silica on the surface of the clay body (all clays contain silica).
A lot of the effects you get in "pit" firing from this and other such techniques is not all that stable over the long haul. Exposure to atmospheric oxygen can change the surfaces of such pieces over time. So most people who are concerend about the "archival" aspects of such pieces seal the surface with an acrylic or wax material. This tendency is kinda' bad if you have pieces in someone's collection or a museum ;)src="http://ceramicartsda...ault/wink.gif"> .
One of the nice properties of the soluble sulphates is their "migration" qualities when applied wet.... sot of handles like watercolors rather than acrylic paint for the carbonate and oxide forms.
Miracle Grow contains a lot of chemistry that is "ceramically active". Look at the label.
Immediate Past President; Potters Council
Professor of Ceramics; New Hampshire Insitute of Art
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