Sandy Henderson on wed 6 feb 02
I just joined this list and have already learned a tremendous
amount. I am hoping someone out there can help me with this: I
recently "inherited" a small amount of some very nice terra cotta
type clay (it came from one of the Cole potteries in Seabrook, NC,
about 25 years ago). It matures about cone 1-2. I need a few good
glaze recipes, or at least one for a clear shiny glaze. I've checked
various sources, including the Clayart archives, and I can't find
any! This will be for oxidation firing, in an electric kiln. Does anyone
fire at cone 1?? If not, is it a matter of fashion, or is there some
other reason? Thank you for any help you can give. I am also
interested in other clays that mature at cone 1-2.
Thanks again,
Sandy
Sandy Henderson
hs@niia.net
1355 W. Springville Rd.
La Porte, IN 46350
219-324-2620
Fredrick Paget on thu 7 feb 02
Generally lowfire terracotta is bisqued to cone 04 and then glaze fired at
cone 06. I never realized what was the reason for this until today when our
ceramics professor addressed the topic. By bisquing higher and using a
lowfire glaze at lower temperature you have far less outgassing from the
body under the glaze and results are generally better. Probably you can get
a good result from this clay at those temperatures.
Terracotta clay is seldom fired into vitrification anyway, It starts to do
a bunch of unlovely things like bloating, warping and melting down if you
take it up too high.
We have a terracotta clay here in Marin that was used to make millions of
bricks a hundred years ago. Half of SanFrancisco is made out of these
bricks. I have this same clay under my land and have experimented with it,
It fires a nice red-orange at cone 04 and vitrifies at about cone 3 as a
dark chocolate color. Bloats frequently at that temperature. I have used it
to make orchid pots - fired at cone 04.
Compounding lead free clear glazes for low fire is difficult and most of
the recipes are propritary, such as Duncan.
Fred
> I recently "inherited" a small amount of some very nice terra cotta
>type clay (it came from one of the Cole potteries in Seabrook, NC,
>about 25 years ago). It matures about cone 1-2. I need a few good
>glaze recipes, or at least one for a clear shiny glaze. I've checked
>various sources, including the Clayart archives, and I can't find
>any! This will be for oxidation firing, in an electric kiln. Does anyone
>fire at cone 1?? If not, is it a matter of fashion, or is there some
>other reason? Thank you for any help you can give. ,,,
>Sandy
From Fred Paget, Marin County, California, USA
Working Potter on thu 7 feb 02
In a message dated 2/7/2002 1:07:01 AM Eastern Standard Time, hs@NIIA.NET
writes:
> I need a few good
> glaze recipes, or at least one for a clear shiny glaze. I've checked
> various sources, including the Clayart archives, and I can't find
> any! This will be for oxidation firing, in an electric kiln. Does anyone
> fire at cone 1?? If not, is it a matter of fashion, or is there some
> other reason? Thank you for any help you can give. I am also
> interested in other clays that mature at cone 1-2.
>
> Thanks again,
> Sandy
>
>
> Dear Sandy,
> If memory serves me ,you might check in archives for Linda Arbuckle's
> majolica glaze for a cone 2.She had her receipe published in several
> publications as well.It is opaque, of course but try omitting the opacifier
> but with a terra cotta it would be a good marriage.Also read on pinholing
> on the archives as well as some of experienced some of that be forewarned.
>
Cindy Strnad on thu 7 feb 02
Dear Sandy,
I believe you can find some glazes that will suit
in Zakin's book on electric kiln firing. Can't
remember the name at the moment, but your library
probably has one, and if not, this is enough info
for them to get it for you. Most of these clays
that mature at ^1-2 end up being fired to ^04-06
with regular low-fire glazes. They do make nice
clays to use in pit firing, so you might consider
that.
Cindy Strnad
Earthen Vessels Pottery
RR 1, Box 51
Custer, SD 57730
USA
cindy@earthen-vessels-pottery.com
http://www.earthen-vessels-pottery.com
John Post on thu 7 feb 02
Hi Sandy,
Here is a cone 1 white glaze that I use over terra cotta clay with my
elementary school students.
It is very glossy and reliable. Underglazes and low fire glazes can be
painted over the top to get bright colors...but then it will probably not be
food safe. IF you omit the superpax, it may be the clear you are looking
for. We use it on sculptures of insects, people etc.
Many commercial terra cotta clays mature in the cone 1-2 range but you will
probably have to test them yourself to make sure. The same goes for
painting glazes over the top of this base. Some underglazes and glazes work
well, while others are too refractory and dry or bubble up...once again you
have to test them first.
+++++++++++++++++++++++++++++++++
+++ * Post's Cone 1 White +++
+++++++++++++++++++++++++++++++++
Date: 12/01/99
Frit 3195 220 20 %
EPK 165 15 %
Flint 55 5 %
Frit 3124 660 60 %
-------- ------
1100 100 %
Superpax 165 15 %
===========================
Chemical Analysis
===========================
Na2O 0.30 Al2O3 0.51 SiO2 3.63
K2O 0.02 B2O3 0.67 ZrO2 0.30
CaO 0.68
Alumina:Silica ratio is 1.00 : 7.11
Neutral:Acid ratio is 1.00 : 3.33
Alkali:Neutral:Acid ratio is 1.00 : 1.18 : 3.93
Expansion coefficient: 71.4 x 10e-7 per degree C
Oxides causing abnormal expansion effects: B2O3
Good luck with it,
John Post
Sterling Heights, Michigan
Sandy said:
I need a few good
glaze recipes, or at least one for a clear shiny glaze. I've checked
various sources, including the Clayart archives, and I can't find
any! This will be for oxidation firing, in an electric kiln. Does anyone
fire at cone 1?? If not, is it a matter of fashion, or is there some
other reason? Thank you for any help you can give. I am also
interested in other clays that mature at cone 1-2.
scott lykens on thu 7 feb 02
I hear the acers library or the old alfred archives have this stuff, like
feet of it. But perhaps research is not your idea of a fun week of hunting.
you could try this out on your body,
80 ff 3124
10 epk
10 flint
its a ron meyers clear, which looks like and should be a cone 04, however,
he told me some students accidentally fired pots to cone 9 and it looked
unscathed. cone 1 being much closer to 04, it should do ok.
if your still uneasy by the 3124 then change it to 3195.
these fritty glazes enjoy a thin application, if your usually into
stonewhere this may seem really odd, you can always add a little gum, or
whatever your favorite suspension agent is.
if you use grog, you may have issues. soem folks seem to find the high boron
frit doing weird stuff to semi vitreous high calcium grog. ie bubble bubble
toil type trouble. >
>
>I just joined this list and have already learned a tremendous
>amount. I am hoping someone out there can help me with this: I
>recently "inherited" a small amount of some very nice terra cotta
>type clay (it came from one of the Cole potteries in Seabrook, NC,
>about 25 years ago). It matures about cone 1-2. I need a few good
>glaze recipes, or at least one for a clear shiny glaze. I've checked
>various sources, including the Clayart archives, and I can't find
>any! This will be for oxidation firing, in an electric kiln. Does anyone
>fire at cone 1?? If not, is it a matter of fashion, or is there some
>other reason? Thank you for any help you can give. I am also
>interested in other clays that mature at cone 1-2.
>
>Thanks again,
>Sandy
>
>
>
>Sandy Henderson
>hs@niia.net
>1355 W. Springville Rd.
>La Porte, IN 46350
>219-324-2620
>
>______________________________________________________________________________
>Send postings to clayart@lsv.ceramics.org
>
>You may look at the archives for the list or change your subscription
>settings from http://www.ceramics.org/clayart/
>
>Moderator of the list is Mel Jacobson who may be reached at
>melpots@pclink.com.
_________________________________________________________________
Join the world’s largest e-mail service with MSN Hotmail.
http://www.hotmail.com
Paul Lewing on thu 7 feb 02
Sandy, check out some of Richard Zakin's books. He fires to cone 3 a lot,
and gives a lot of recipes for that range. Any of the really glossy glazes
at cone 3 should be OK at cone 2.
Paul Lewing, Seattle
Ron Roy on sun 10 feb 02
This looks like it might be a stable glaze.
When calculating to see if there is enough silica for stability the pax
should be left out as the silica in the zirconium silicate does not become
part of the glaze - well most of it anyway.
By the way - Johns limited experiments tended to show zirconium silicate
has an adverse effect on durability.
If anyone is going to load this glaze up with colouring oxides it should be
tested for release - unless of course it is not where food can come in
contact.
RR
>+++++++++++++++++++++++++++++++++
>+++ * Post's Cone 1 White +++
>+++++++++++++++++++++++++++++++++
>
>Date: 12/01/99
>
> Frit 3195 220 20 %
> EPK 165 15 %
> Flint 55 5 %
> Frit 3124 660 60 %
> -------- ------
> 1100 100 %
>
> Superpax 165 15 %
>
>===========================
> Chemical Analysis
>===========================
>
> Na2O 0.30 Al2O3 0.51 SiO2 3.63
> K2O 0.02 B2O3 0.67 ZrO2 0.30
> CaO 0.68
>
> Alumina:Silica ratio is 1.00 : 7.11
> Neutral:Acid ratio is 1.00 : 3.33
> Alkali:Neutral:Acid ratio is 1.00 : 1.18 : 3.93
>
>Expansion coefficient: 71.4 x 10e-7 per degree C
>Oxides causing abnormal expansion effects: B2O3
Ron Roy
RR# 4
15084 Little Lake Rd..
Brighton,
Ontario, Canada
KOK 1H0
Residence 613-475-9544
Studio 613-475-3715
Fax 613-475-3513
| |
|
