Butch Welch on thu 29 may 03
I have read posters that take a pot after it has been fired and re-fired it
to a low cone level to bring out additional glaze effects. I am assuming
that it cool down from normal cut off ( no controlled cool down). I have
also read with interest the effects of a slow programmed cool down. My
question is do they both have the same effect on the end result of the
appearance of the glaze.
I can do a control test but it will be some time before I can do it due to
the fact I do not fire that often.
Has anyone else don't this comparison?
Regards, Butch
"Any thing you pay a bad worker is to much, But you can not pay a good
worker enough!"
John Hesselberth on thu 29 may 03
On Thursday, May 29, 2003, at 04:23 PM, Butch Welch wrote:
> My
> question is do they both have the same effect on the end result of the
> appearance of the glaze.
Hi Butch,
I am guessing a bit here, but I think not. The refiring technique
seems to work well on strengthening the color of iron reds. I believe
you could match it will slow cooling, but it might take some
experimenting to get exactly the right cooling profile--it may well be
different than the profile for what works in next paragraph.
The other reason to slow cool is to develop mattes when using a durable
matte glaze recipe. You need time to let tiny crystals form and grow
while the glaze is still molten. I would guess you could NOT get this
effect from refiring. If you cool one of those glazes rapidly it will
be glossy. I am guessing it would still be glossy after refiring--but
maybe not--that would be an interesting experiment.
Regards,
John
http://www.frogpondpottery.com
http://www.masteringglazes.com
Ron Roy on sat 31 may 03
Hi Butch,
A couple of points.
When refiring it is important not to fire to high - otherwise you start
remelting the crystals which may already have started to grow - depends on
the glaze and how easily it melts - lots of boron and/or KNaO means it will
melts sooner than others.
Most notes on refiring to get more and bigger crystals (striking) say a low
bisque - you will find out which temperature works best by trial and error.
When refiring to grow crystals the crystals will form and/or grow on the
way up and on the way down but there will be an optimum temperature at
which the crystals will grow fastest (I have no idea about this but it will
be different for each glaze) - if you can discover this temperature you can
simply go to it and hold there for different lengths of time. Crystals rely
on silica from the surrounding glaze so crystal growth is limited to time
to form and available silica.
Because the crystal robs silica from surrounding glaze that part of the
glaze becomes less durable - if you try the vinegar test you may be able to
see this in some cases.
So yes - the time you take to get to temperature when refiring is important
- fast is not as good as slow - and the time cooling - down to when the
glaze freezes - is better slow if you want bigger crystals - but holding at
the right time would be the best.
RR
>I have read posters that take a pot after it has been fired and re-fired it
>to a low cone level to bring out additional glaze effects. I am assuming
>that it cool down from normal cut off ( no controlled cool down). I have
>also read with interest the effects of a slow programmed cool down. My
>question is do they both have the same effect on the end result of the
>appearance of the glaze.
>
>I can do a control test but it will be some time before I can do it due to
>the fact I do not fire that often.
>
>Has anyone else don't this comparison?
>
>Regards, Butch
>"Any thing you pay a bad worker is to much, But you can not pay a good
>worker enough!"
Ron Roy
RR#4
15084 Little Lake Road
Brighton, Ontario
Canada
K0K 1H0
Phone: 613-475-9544
Fax: 613-475-3513
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