Jim Willett on sun 31 jul 05
Speaking of Fool's Gold glazes, I've sent a picture up to flickr
http://www.flickr.com/photos/clayart/ of a close up of a "Fools Gold" effect
I got with an application of two of our glazes and a topping of a high Red
Iron Oxide glaze. I hadn't really thought about "Fools Gold" until you
mentioned it Steve. There are a few other pictures of this glaze at
http://www.outofthefirestudio.com/photogallery.htm if you scroll over to the
right to pictures 13,14, and 15. These are all Cone 6 ish oxidation.
Interestingly, if you fire a few degrees higher the gold goes away and you
wind up with a beautiful blue.
Jim Willett
Out of the Fire Studio
Edmonton, Alberta
http://www.outofthefirestudio.com
http://potblog.outofthefirestudio.com
Steve Slatin wrote.....
".......... -- the second most prevalent element in rutile is iron, which
makes most things go brown in oxidation below cone 10. Iron sulfide,
(FeS2), interestingly, is 'fools gold.' The iron and sulpher (which has a
native color of yellow) in this tight crystalline form become gold in color.
(the crystals are isometric ) The
crystals can be extremely regular.
3 -- If you look with a loupe or other magnifier at the gold parts of a
rutile wash on your glaze, you'll see a magnificent series of crystals
apparently forming within the glaze. Each visible surface seems quite
square, as would be expected of an isometric crystal.
Now, some may condemn me for trying to conduct science in a public forum.
But points 1 and 2 are well- established, and point 3 is something you can
confirm yourself. I'm going to say, in answer to your question "what makes
it go gold" that a good hypothesis would be that the Ti and/or Fe are
forming tiny isometric crystals within the glaze at or near its
vitrification temperature, and are suspended inside of the cooling glaze,
where their perfectly formed, smooth, flat surfaces reflect brightly the
yellowish color we see as 'gold.'....................."
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Steve Slatin on sun 31 jul 05
Jim --
Wonderful glazes, and while it's hard to tell exactly
what's going on (even in the close ups) it seems you
have something with tiny crystal formation going on
there. The 'starry night' glaze was the one that
really got me, though. I presume that the gold in
that one is rutile also?
It is a (weak) confirmation of the crystal theory that
the gold color goes away with higher firing. Crystal
formation is highly temperature dependent, and a
little extra (or longer) heat could either bring the
mineral more completely into solution in the melt (so
that it wouldn't have the 'seeds' to form crystals) or
absorb it into the more amorphous glass body.
I have devised a simple (& crude!) test to see what
the correlation of a 'gold' color from rutile,
titanium alone, and iron alone, and will run it in my
next glaze load.
-- Steve Slatin
--- Jim Willett wrote:
> Speaking of Fool's Gold glazes, I've sent a picture
> up to flickr
> http://www.flickr.com/photos/clayart/ of a close up
> of a "Fools Gold" effect
> I got with an application of two of our glazes and a
> topping of a high Red
> Iron Oxide glaze. I hadn't really thought about
> "Fools Gold" until you
> mentioned it Steve. There are a few other pictures
> of this glaze at
> http://www.outofthefirestudio.com/photogallery.htm
> if you scroll over to the
> right to pictures 13,14, and 15. These are all Cone
> 6 ish oxidation.
> Interestingly, if you fire a few degrees higher the
> gold goes away and you
> wind up with a beautiful blue.
>
> Jim Willett
>
Steve Slatin --
Frail my heart apart and play me little Shady Grove
Ring the bells of Rhymney till they ring inside my head forever
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