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Copper sulfate?


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#1 Iforgot

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Posted 03 December 2012 - 10:28 PM

Hey world,

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.



Thanks!

Darrel
Derek VonDrehle

Raku, Pit fired, Majolica, and Stoneware ceramic artisit

#2 weeble

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Posted 04 December 2012 - 04:21 AM

What, you never heard of google? According to wiki, there are two separate chemical forms of copper sulfate, but it starts loosing water molecules before it melts bla bla bla insert geekspeek chemistry noise here.

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.
Maryjane Carlson

Whistling Fish Pottery

#3 JBaymore

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Posted 04 December 2012 - 08:01 AM

Copper sulfate does not "flux" per se if you mean what temperature does it melt at. It is not a glass former. What it will supply once heated in the kiln is copper oxide (CuO). Copper oxide is a fluxing agent on silica, which is a glass former.

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.

best,

.........................john
John Baymore
Immediate Past President; Potters Council
Professor of Ceramics; New Hampshire Insitute of Art

http://www.JohnBaymore.com




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