Greg Lamont on fri 18 sep 98
Here's one for the "glaze gurus" out there. I have been experimenting with
a glaze for cone 6 oxidation called Persimmon and have two questions about
it. This is one of those glazes that looks pretty horrible after firing to
cone 6 in oxidation, but looks terrific after re-firing it to cone
06--colorwise, anyway.
Question 1: what--chemically or physically--accounts for this change of
color?
Question 2: Some of the pieces--but not all--seem to have very small
blisters on the glaze surface. What might have caused these and would
re-firing to a slightly hotter temp and/or soaking the kiln for a time heal
these over without losing the fabulous color? The recipe is as follows:
Persimmon
---------
6 Ox. or Red.
Gerstley borate 47
EPK 23
Flint 30
--------
100
Red iron oxide 10
Soda ash 0.2
Thanks for any insight you can provide.
Greg
Ron Roy on sun 20 sep 98
Hi Greg,
When you refire to 06 you are giving the iron crystals on the surface of
the glaze more time to grow. This is called striking I think - sometimes
used to get more red in copper red glazes and to grow larger crystals in
crystalline glazes. If you have a controller you could cool to 1000C and
hold for a couple of hours and you would get a similar result.
Blisters - this may be a bisque firing problem. If soaking or refiring does
not solve the problem then we need to look at your bisque schedule.
Especially if you are using a body with any fireclay and/or red clay in it.
This glaze is not durable - oversupplied with Boron and undersupplied with
alumina and silica at cone 6. The expansion looks like it could be on the
low side so I would recommend some serious fit testing on any clays you are
using
>----------------------------Original message----------------------------
>Here's one for the "glaze gurus" out there. I have been experimenting with
>a glaze for cone 6 oxidation called Persimmon and have two questions about
>it. This is one of those glazes that looks pretty horrible after firing to
>cone 6 in oxidation, but looks terrific after re-firing it to cone
>06--colorwise, anyway.
>
>Question 1: what--chemically or physically--accounts for this change of
>color?
>Question 2: Some of the pieces--but not all--seem to have very small
>blisters on the glaze surface. What might have caused these and would
>re-firing to a slightly hotter temp and/or soaking the kiln for a time heal
>these over without losing the fabulous color? The recipe is as follows:
>Persimmon
>---------
>6 Ox. or Red.
>
>Gerstley borate 47
>EPK 23
>Flint 30
> --------
> 100
>
>Red iron oxide 10
>Soda ash 0.2
>
>Thanks for any insight you can provide.
>Greg
Ron Roy
93 Pegasus Trail
Scarborough, Ontario
Canada M1G 3N8
Tel: 416-439-2621
Fax: 416-438-7849
Web page: http://digitalfire.com/education/people/ronroy.htm
Ron Roy on tue 22 sep 98
Hi Greg,
When you refire to 06 you are giving the iron crystals on the surface of
the glaze more time to grow. This is called striking I think - sometimes
used to get more red in copper red glazes and to grow larger crystals in
crystalline glazes. If you have a controller you could cool to 1000C and
hold for a couple of hours and you would get a similar result.
Blisters - this may be a bisque firing problem. If soaking or refiring does
not solve the problem then we need to look at your bisque schedule.
Especially if you are using a body with any fireclay and/or red clay in it.
This glaze is not durable - oversupplied with Boron and undersupplied with
alumina and silica at cone 6. The expansion looks like it could be on the
low side so I would recommend some serious fit testing on any clays you are
using
>----------------------------Original message----------------------------
>Here's one for the "glaze gurus" out there. I have been experimenting with
>a glaze for cone 6 oxidation called Persimmon and have two questions about
>it. This is one of those glazes that looks pretty horrible after firing to
>cone 6 in oxidation, but looks terrific after re-firing it to cone
>06--colorwise, anyway.
>
>Question 1: what--chemically or physically--accounts for this change of
>color?
>Question 2: Some of the pieces--but not all--seem to have very small
>blisters on the glaze surface. What might have caused these and would
>re-firing to a slightly hotter temp and/or soaking the kiln for a time heal
>these over without losing the fabulous color? The recipe is as follows:
>Persimmon
>---------
>6 Ox. or Red.
>
>Gerstley borate 47
>EPK 23
>Flint 30
> --------
> 100
>
>Red iron oxide 10
>Soda ash 0.2
>
>Thanks for any insight you can provide.
>Greg
Ron Roy
93 Pegasus Trail
Scarborough, Ontario
Canada M1G 3N8
Tel: 416-439-2621
Fax: 416-438-7849
Web page: http://digitalfire.com/education/people/ronroy.htm
Gregory D Lamont on mon 20 dec 99
Dear Clayarters,
A potter friend of mine has asked me to try to track down any information I
can about the following:
A cone 10 reduction glaze called "Michigan Blue". He's seeking the recipe
for this one.
Any information on "flambe" glazes. These sound to me to be in the copper
red family of glazes, but with some differences. He's looking for a
typical recipe and any firing advice one might be willing to give.
TIA
Greg
gdlamont@iastate.edu
http://www.ourwebpage.net/greglamont/
Mailing address:
Greg Lamont
3011 Northwood Drive
Ames, IA 50010-4750
(515) 233-3442
| |
|
