Clay on mon 28 may 12
Hello one and all,
I'm once firing a standard terracotta body to cone 03.
All the glaze tests are done in an electric kiln, the finals will be LPG
fired.
So .. I've been playing with crawl glazes.
My first little number works well on bare body.
Beads up into nice little white balls that even cling to throwing rings
to make pretty pretty patterns :)
Lead Bisilicate 80%
Hyplas 20%
Tin Oxide 5%
Magnesium Carbonate 11.2%
Next step ... throw my lovely new white crawl glaze, over the top of my
shiny shiny black glaze.
Worked well on flat tiles: a completely different effect mind, as all
those balls slip back flat and leave a wonderfully broken pretty pattern.
(pretty being my word of the day you notice !)
But now I try in a simple cylindrical test pot .....
waaaah ... all the crawl glaze just curls up and falls off.
Way before it even gets a glimpse of the kiln !
I've had glazes fall of before, but usually because they don't shrink
enough, this one is shrinking waaaaay to much.
Admittedly, I am laying this glaze on thick. Very thick.
Also, I've never worked with Magnesium Carbonate before.
Also aware that the black glaze in between the pot body and the crawl
glaze may present binding issues .
So ... is there an 'anti-bentonite' I can use that would reduce the
shrinkage without affecting chemistry too much ? (I have tried
replacing the hyplas in recipe for kaolin... )
Is there anything I can try to improve binding ?
Full blurb here, for those who cannot sleep :
http://blog.netshed.co.uk/?page_id=3D22
Black gloss recipe for reference :
Potclays 1137 Terracotta 14.5%
Cobalt Carbonate 0.7%
mangenese Dioxide 1.1%
Iron Oxide Red 3.6%
Lead Bisilicate 80%
Many Thanks
Simon
:)
Sumi von Dassow on mon 28 may 12
Clay
CMC?
Sumi
> Hello one and all,
>
> I'm once firing a standard terracotta body to cone 03.
> All the glaze tests are done in an electric kiln, the finals will be LPG
> fired.
>
> So .. I've been playing with crawl glazes.
> My first little number works well on bare body.
> Beads up into nice little white balls that even cling to throwing rings
> to make pretty pretty patterns :)
>
> Lead Bisilicate 80%
> Hyplas 20%
> Tin Oxide 5%
> Magnesium Carbonate 11.2%
>
> Next step ... throw my lovely new white crawl glaze, over the top of my
> shiny shiny black glaze.
> Worked well on flat tiles: a completely different effect mind, as all
> those balls slip back flat and leave a wonderfully broken pretty pattern.
> (pretty being my word of the day you notice !)
>
> But now I try in a simple cylindrical test pot .....
> waaaah ... all the crawl glaze just curls up and falls off.
> Way before it even gets a glimpse of the kiln !
>
> I've had glazes fall of before, but usually because they don't shrink
> enough, this one is shrinking waaaaay to much.
>
> Admittedly, I am laying this glaze on thick. Very thick.
> Also, I've never worked with Magnesium Carbonate before.
> Also aware that the black glaze in between the pot body and the crawl
> glaze may present binding issues .
>
> So ... is there an 'anti-bentonite' I can use that would reduce the
> shrinkage without affecting chemistry too much ? (I have tried
> replacing the hyplas in recipe for kaolin... )
>
> Is there anything I can try to improve binding ?
>
> Full blurb here, for those who cannot sleep :
> http://blog.netshed.co.uk/?page_id=3D22
>
>
> Black gloss recipe for reference :
>
> Potclays 1137 Terracotta 14.5%
> Cobalt Carbonate 0.7%
> mangenese Dioxide 1.1%
> Iron Oxide Red 3.6%
> Lead Bisilicate 80%
>
> Many Thanks
> Simon
> :)
>
>
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