L. P. Skeen on sat 26 feb 05
I got a call a few days ago from a local person who wanted me to come =
teach her how to use her Raku kiln. She is using several very common =
glazes which recipes appear in Steve Branfman's Raku book. I have used =
these same glazes before, but have never had the glaze react the way =
this one did. Here is the recipe:
Del Favero Luster
GB 80
Cornwall Stone 20
Copper carb 2
This recipe SHOULD be a glossy metallic if it gets good redux.
What happened with this particular load happened to every piece in the =
load. She's making pendants and jewelry pieces, so they're all small, =
flat shapes with stamped texture. The top of each piece was coated in =
glaze with a paintbrush, and they were glazed yesterday afternoon. When =
they were fired this morning, the base of the glaze stayed put, and each =
piece is glossy. HOWEVER - it appears that the COLORANT (copper) =
migrated. So each piece has a clear coat of gloss glaze with these =
islands (freckles and spots) of copper. I have never seen ANY glaze do =
this. It is NOT crawling - if it were, the glaze base would have popped =
up as well, and it did not. The weird thing is that in the very next =
firing, the glaze behaved perfectly and we got lots of copper-penny and =
rainbowy effects on a solid gloss glaze.
I am attempting to get a scan of one of these pieces in case anybody is =
interested in seeing this fiasco. What I want to know is what happened =
exactly, and why. Clues please?
Thanks!
L
Gene Arnold on sun 27 feb 05
Lisa
I have gotten this sometimes when the glaze has been mixed for a while. I
just sieve all my raku glazes now just before using them and it seems to
make all the difference. The GB has a tendency to clump up after it has been
mixed and sits for awhile. Just stirring doesn't seem to do the trick. Try
sieving and see if that helps.
Gene & Latonna
mudduck@mudduckpottery.com
www.mudduckpottery.com
----- Original Message -----
From: "L. P. Skeen"
To:
Sent: Saturday, February 26, 2005 8:15 PM
Subject: Raku glaze weirdness
I
william schran on sun 27 feb 05
LP wrote:> When they were fired this morning, the base of the glaze
stayed put, and each piece is glossy. HOWEVER - it appears that the
COLORANT (copper) migrated. So each piece has a clear coat of gloss
glaze with these islands (freckles and spots) of copper. <
Could be the glaze was over fired, small work would heat up much faster.
Bill
L. P. Skeen on tue 1 mar 05
Thanks y'all for all the responses. I am passing them on to the other
person as well. :)
L
----- Original Message -----
From: "Gene Arnold"
> Lisa
>
> I have gotten this sometimes when the glaze has been mixed for a while. I
> just sieve all my raku glazes now just before using them
Wally on wed 2 mar 05
Copper in low-temp firings often cause unpredictable and
unrepeatable results.
My guess is that volatalised copper fumes kind of crystallized on
the surface of the molten glaze, concentrating in the spots you
mentionned.
Could be.
Wally.
--- In clayart@yahoogroups.com, william schran wrote:
> LP wrote:> When they were fired this morning, the base of the glaze
> stayed put, and each piece is glossy. HOWEVER - it appears that
the
> COLORANT (copper) migrated. So each piece has a clear coat of
gloss
> glaze with these islands (freckles and spots) of copper. <
>
> Could be the glaze was over fired, small work would heat up much
faster.
> Bill
>
>
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