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copper reds and red hots

updated sat 9 aug 08


Wyndham Dennison on fri 8 aug 08

> Date: Thu, 7 Aug 2008 10:24:18 +0200
> From: jean szostek
> Subject: Re: Copper Red, Red Hot
> hi wyndham,
> first about the tin : if you use tin you dont have transparency in de glaze,
> and it becomes more dark red
> it wonders me , that it becomes darker.
> your idea about the calcined kaolin is maybe good, but if you cut the
> fluidity of the glaze, the beautiful colors disapears,
> on this mater im still experimenting - im only six years potter- so ill
> still have to learn mutch
> my next kiln i tough will try the calcined kaolin, maybe with different
> amounts
> i let you now, how it turns out
> thank you for the advise jean
Jean, calcining the kaolin will not or I should say should not change
the glaze except that when dipping it will not cake and crack on drying
before firing. Just from my experience, I have had glazes to peel off or
pop of from the pot on over hanging lips with a large % of raw
clay(above 10%) in the recipe during firing. Since the clay will shrink
from raw glaze to the bisque stage of the glaze firing and I use a
rather heavy application, it has served me well to use the same amt of
clay in the glaze except that half has been calcined and the other half
raw from the bag. There is a slight difference in amt of clay in the
glaze because the weight of raw clay includes some moisture and the
calcined clay does not. If it becomes less fluid just back off a % or
two to rebalance for the look you want.
On a side note I have a shino recipe that if I double the ball
clay(35+%) in the recipe I get a nice crawl to little balls on the pot
I think you are very perceptive on the transparency issue on the copper
reds and the use of tin may well be something that allows the reds in a
wider glaze palette at the cost of transparency and color fidelity. I
will test and let you know how my kiln reacts to the glaze , all the
best Wyndham