Josh Berkus on wed 12 sep 07
John,
> I found that Cone 5 B
> mix was not fully vitrified (leak-proof without glaze) until about
> cone 7.
Oh? That's bad news; I have 2 shelves of pots made with Cone 5 B-mix waiting
to be fired to Cone 6. I'm used to the Cone 10 B-Mix at 2325F, where it's
hard, vitreous and chip-resistant, like porcelain.
Should I be using a different white-body clay for Cone 6? Which? I prefer
using a grog-free white body stoneware or synthetic porcelain.
--
The Fuzzy Chef
San Francisco
Nancy on wed 12 sep 07
I've been using Cone 6 B Mix for about 8 years and this is the first
I've heard of it not being vitrified unless it reaches cone 7. I've
never had a problem using them in the microwave, oven, etc. I know clay
that is not vitrified will generally have problems in the microwave. I
use this clay and the new B Mix with grog for 95% of my pieces and my
students use the same clay. I do, however, fire to a hot cone 6.
Nancy
Josh Berkus wrote:
> John,
>
>
>> I found that Cone 5 B
>> mix was not fully vitrified (leak-proof without glaze) until about
>> cone 7.
>>
>
> Oh? That's bad news; I have 2 shelves of pots made with Cone 5 B-mix waiting
> to be fired to Cone 6. I'm used to the Cone 10 B-Mix at 2325F, where it's
> hard, vitreous and chip-resistant, like porcelain.
>
> Should I be using a different white-body clay for Cone 6? Which? I prefer
> using a grog-free white body stoneware or synthetic porcelain.
>
> --
> The Fuzzy Chef
> San Francisco
>
> ______________________________________________________________________________
> Send postings to clayart@lsv.ceramics.org
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>
John Hesselberth on thu 13 sep 07
On Sep 12, 2007, at 2:05 PM, Josh Berkus wrote:
> Should I be using a different white-body clay for Cone 6? Which?
> I prefer
> using a grog-free white body stoneware or synthetic porcelain.
Hi Josh,
Sorry, I don't know the answer to your question because I don't know
what clays are available to you nor am I very familiar with west
coast clays. I would look for one that says it has 2% or less water
absorption at whatever cone you want to glaze fire to--6 in your
case. Then get a sample and test that yourself as the published
numbers are not always highly accurate. Also make a vase, fill it
with water, and let it set on a piece of newspaper for a few days.
Examine for leakage. Now if you really want an iron clad test, fill
your vase with lamp oil instead of water. Thin oils can work their
way out of most anything unless the body is very tight. People who
make oil lamps from undervitrified clay are playing with fire in more
ways than one.
Regards,
John
John Hesselberth
www.frogpondpottery.com
"Man is a tool-using animal....without tools he is nothing, with
tools he is all" .... Thomas Carlyle
Carole Fox on thu 13 sep 07
On Wed, 12 Sep 2007 11:05:13 -0700, Josh Berkus wrote:
>John,
>
>> I found that Cone 5 B
>> mix was not fully vitrified (leak-proof without glaze) until about
>> cone 7.
>
>Oh? That's bad news; I have 2 shelves of pots made with Cone 5 B-mix
waiting
>to be fired to Cone 6. ...
>The Fuzzy Chef
>San Francisco
Fuzzy - I've been using Laguna's Eastern version of ^5 B-mix for several
years, normally firing to shelf cone 6. While I've never made an item in
this body without glaze, I've made lots of glazed mugs, bowls, and vases
from ^5 B-mix all of which hold liquid without leakage. I use one of the
mugs everyday in the microwave for my tea. I say, go for it.
Carole Fox
Dayton, OH
Dolita Dohrman on thu 13 sep 07
One added piece of advice....DO NOT go by the clay manufacturers'
percentages for absorption. Most of them are way off. I think they
do it to sell range clays to ^6 potters. Just my opinion. I have
done numerous tests on clays and found absorption to be quite a bit
higher than they state. One company...Highwater...is usually pretty
much on though. That being said...I have used B-mix 5 and did not
have any trouble. I think you should keep using it if you like it.
Dolita
On Sep 13, 2007, at 11:10 AM, John Hesselberth wrote:
> On Sep 12, 2007, at 2:05 PM, Josh Berkus wrote:
>
>> Should I be using a different white-body clay for Cone 6? Which?
>> I prefer
>> using a grog-free white body stoneware or synthetic porcelain.
>
>
> Hi Josh,
>
> Sorry, I don't know the answer to your question because I don't know
> what clays are available to you nor am I very familiar with west
> coast clays. I would look for one that says it has 2% or less water
> absorption at whatever cone you want to glaze fire to--6 in your
> case. Then get a sample and test that yourself as the published
> numbers are not always highly accurate. Also make a vase, fill it
> with water, and let it set on a piece of newspaper for a few days.
> Examine for leakage. Now if you really want an iron clad test, fill
> your vase with lamp oil instead of water. Thin oils can work their
> way out of most anything unless the body is very tight. People who
> make oil lamps from undervitrified clay are playing with fire in more
> ways than one.
>
> Regards,
>
> John
>
> John Hesselberth
> www.frogpondpottery.com
>
> "Man is a tool-using animal....without tools he is nothing, with
> tools he is all" .... Thomas Carlyle
>
> ______________________________________________________________________
> ________
> 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
> melpots2@visi.com
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