David Hewitt on mon 9 sep 02
We have all, at some time or another, had unexpected glaze results even
when we are using one of our well tried glazes.
This may be because of a mistake in mixing a new batch, a new supply of
some material which happens to have a different analysis, a change in
firing, etc..
These aspects have been the subject of many threads, but one which does
not get mentioned is to ask if the glaze has been standing for some time
and how it was brought back into full suspension before being used
again. Certainly a glaze mix that has not been fully re-constituted can
give odd results.
I would be interested to hear what others do in this respect. Do they
always re-sieve as distinct from just stir up with a stick? Does this
depend on the glaze or when it was last used? What sieve do you use for
glaze mixing? I think a while ago I saw a comment that a course kitchen
sieve is all you need if the glaze is to be fired to cone 8, or
something like that.
For myself, I will re-sieve unless the glaze has been used very recently
and on stirring with a stick, the stick comes out with none of the glaze
sticking to it. The sieve I use is a 100 mesh. Why a 100, I do not know.
This is how I started some 25 years ago and have continued ever since.
--
David Hewitt
David Hewitt Pottery ,
7 Fairfield Road, Caerleon, Newport,
South Wales, NP18 3DQ, UK. Tel:- +44 (0) 1633 420647
FAX:- +44 (0) 870 1617274
Web site http://www.dhpot.demon.co.uk
Barbara Mueller on mon 9 sep 02
I'm glad that you brought this up as I was thinking about this yesterday
and wondering what steps are really necessary. I glaze one to two times
a month. I sieve each of my glazes twice before I use them. I think my
screen is 100 also. If I am using six glazes this ends up taking a lot
of time. I noticed that if I mix my glazes well I get up the bottom
residue. So am I sieving unnecessarily?
And after opening the kiln this morning I saw some minor pitting
happening with a glaze firing to Cone 6 using the same ramp, the same
clay and the same glazes as I have been using previously. The pieces
are not ruined but I notice it.
Any ideas. I washed the pieces before I glazed them and let them dry so
I don't think there was dust. I wish I had more experience, more of a
trained eye. It gets frustrating not to be able to make sense of it.
I did hear some thermal type noise as the kiln was doing its slow
cooling at around 1500 degrees but I am not usually in the room with the
kiln as it is cooling and maybe it always make that noise. Nothing was
broken. Maybe it's a clue to the slight pitting though.
B
-----Original Message-----
From: Ceramic Arts Discussion List [mailto:CLAYART@LSV.CERAMICS.ORG] On
Behalf Of David Hewitt
Sent: Monday, September 09, 2002 1:38 AM
To: CLAYART@LSV.CERAMICS.ORG
Subject: Those unexpected glaze results
We have all, at some time or another, had unexpected glaze results even
when we are using one of our well tried glazes.
This may be because of a mistake in mixing a new batch, a new supply of
some material which happens to have a different analysis, a change in
firing, etc..
These aspects have been the subject of many threads, but one which does
not get mentioned is to ask if the glaze has been standing for some time
and how it was brought back into full suspension before being used
again. Certainly a glaze mix that has not been fully re-constituted can
give odd results.
I would be interested to hear what others do in this respect. Do they
always re-sieve as distinct from just stir up with a stick? Does this
depend on the glaze or when it was last used? What sieve do you use for
glaze mixing? I think a while ago I saw a comment that a course kitchen
sieve is all you need if the glaze is to be fired to cone 8, or
something like that.
For myself, I will re-sieve unless the glaze has been used very recently
and on stirring with a stick, the stick comes out with none of the glaze
sticking to it. The sieve I use is a 100 mesh. Why a 100, I do not know.
This is how I started some 25 years ago and have continued ever since.
--
David Hewitt
David Hewitt Pottery ,
7 Fairfield Road, Caerleon, Newport,
South Wales, NP18 3DQ, UK. Tel:- +44 (0) 1633 420647
FAX:- +44 (0) 870 1617274
Web site http://www.dhpot.demon.co.uk
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John Hesselberth on mon 9 sep 02
Hi David,
I first stir with a stick or a drill mixer and then re-sieve through an
80 mesh screen. I find that with some glazes I can get by with mixing
only and on others I really get burned if I don't re-sieve. Just last
week I only wanted to glaze one pot with a particular glaze. It visually
looked like my stirring did the trick, but it didn't. Another pot meets
the hammer.
So my rule is to re-sieve and I have only myself to blame when I get
lazy and don't do it.
I speculate that those who say glazes sometimes "age" on them may not be
re-sieving.
Regards,
John
On Monday, September 9, 2002, at 05:38 AM, David Hewitt wrote:
> I would be interested to hear what others do in this respect. Do they
> always re-sieve as distinct from just stir up with a stick? Does this
> depend on the glaze or when it was last used? What sieve do you use for
> glaze mixing? I think a while ago I saw a comment that a course kitchen
> sieve is all you need if the glaze is to be fired to cone 8, or
> something like that.
Frog Pond Pottery
PO Box 88
Pocopson, PA 19366
Fax or phone: 610-388-1254
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