asim mahmood on mon 22 mar 10
I have been using clear glaze as a liner glaz=
=3D
e for my medium size bowels for the past few years and there have never bee=
=3D
n any problem with the glaze appearance what so ever. For the last two firi=
=3D
ng the liner glaze on walls and at the base of bowels and pitcher have been=
=3D
turning cloudy ( the effect is more pronounced once you travel towards the=
=3D
base )=3D2C it has happened only to few of the pots on each shelf and rem=
ai=3D
ning pots turned out to be perfect. There was no change in glaze or clay re=
=3D
cipe except this time I resorted to 15 minutes soaking at cone 6 and slow c=
=3D
ooling.
I then mixed a fresh batch for the liner glaz=
=3D
e and fired over this weekend but result was not much different than before=
=3D
=3D2C glaze on some of the pots turned cloudy and with a bit movement insid=
e.=3D
With this backdrop could any one pin point me as to what causes this cloud=
=3D
iness in general ? Thanks in advance.
=3D20
Asim Mahmood. =3D20
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John Hesselberth on mon 22 mar 10
On Mar 22, 2010, at 9:57 AM, asim mahmood wrote:
> I have been using clear glaze as a liner =3D
glaze for my medium size bowels for the past few years and there have =3D
never been any problem with the glaze appearance what so ever. For the =3D
last two firing the liner glaze on walls and at the base of bowels and =3D
pitcher have been turning cloudy ( the effect is more pronounced once =3D
you travel towards the base ), it has happened only to few of the pots =3D
on each shelf and remaining pots turned out to be perfect. There was no =3D
change in glaze or clay recipe except this time I resorted to 15 minutes =
=3D
soaking at cone 6 and slow cooling.
> I then mixed a fresh batch for the liner =3D
glaze and fired over this weekend but result was not much different than =
=3D
before, glaze on some of the pots turned cloudy and with a bit movement =3D
inside. With this backdrop could any one pin point me as to what causes =3D
this cloudiness in general ? Thanks in advance.
>=3D20
Hi Asim,
Certainly slow cooling could cause this. Potters often do this on =3D
purpose to increase the mattness of a glaze. When you want a clear glaze =
=3D
you either need to cool more rapidly or reformulate your glaze to =3D
minimize crystallization (devitrification) during cooling. Control of =3D
the cooling to give the results you want is, in my opinion, the most =3D
important part of the firing cycle in electric kilns.
Regards,
John
John Hesselberth
john@frogpondpottery.com
=3D93The art of taxation consists in so plucking the goose as to obtain =3D
the largest possible amount of feathers with the smallest possible =3D
amount of hissing=3D94
Jean Baptiste Colbert
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