[Clayart] Wide range clay

David Woof woofpots at hotmail.com
Mon Jan 24 02:58:55 UTC 2022

Hi Gayle, Everyone.......

As raw materials change or become unavailable, so must the formulations of the clay bodies. It is the natural order of things, and the providers do their best to please and provide.
But as we have been discussing, a change in materials can change absorption % and so cause a potential for "Wet foot" leakage.

It is good to throw a few 4" test cup forms from the new batch of clay before a production run, place them in different locations in the kiln and fire them along with pottery from the previous clay batch.
After high firing, fill these test cups with water and let them sit at least 24 hours on a sheet of white paper.   If they are "wet or damp foot" the paper will be wrinkled where they were placed.

Note; fill cups with tepid water to avoid exterior condensation of atmospheric moisture which can run down and  skew the leakage test.

Your Ceramic materials provider could provide you with some info re change, but the actual formula is not open source.

I haven't used commercial B-Mix since before 2012 and as I recall Laguna produced a cone 5 B-mix that would fire to ^6,

And I'm not remembering if the B-Mix ^10 was touted as ^6 -10.    Your materials catalog, someone on this list, or supplier could speak to that.

I only used the Cone 10 B-Mix to add 25% of a coarse red cone 10 native clay that I was digging up in the mountains above the Rio Verde, in Arizona.  Great in the wood fire I was doing at the time.

Short Rant:........Being interested in the intrinsic physical qualities and character of raw materials, as well as the Chemical formulas assigned to them, I always give a second and third look at the substitution recommendations a calculation program provides.

I do my substitution calculations the old "do the Math" way.

What does one learn of decision-making value by hitting a few keys and ordering whatever comes up on the screen.
Later...... while scratching one's head and asking why did this great Clay Body or Glaze that worked so well suddenly change?

From: Clayart <clayart-bounces at lists.clayartworld.com> on behalf of Gayle Bair <gayle.claybair at gmail.com>
Sent: Friday, January 21, 2022 1:31 PM
To: Clayart international pottery discussion forum <clayart at lists.clayartworld.com>
Subject: Re: [Clayart] Wide range clay

I’ve not had any problem with cone 6 B-mix.  I’ve been using it for years. Have they changed the formula?

Sent from my iPhone

> On Jan 21, 2022, at 10:57 AM, dannon at ccrtc.com wrote:
> I have found that clay advertised at 6- 10 is not satisfactory at cone
> 6.  They seem at bit "soft" at 6, plus many glazes do not do well on
> them at cone 6.  A lot of crackling.  Looks good sometimes, but, ummmm -
> for food containers, not so great.  My experience/opinion.
> Dannon Rhudy
>> On 2022-01-21 10:39 am, Vanessa Greene wrote:
>> Any thoughts from all you experienced potters about those clays that
>> are marketed as a wide ranging temp clay, cone 6-10…..are they really
>> fully vitrified at cone 6? I hear very different opinions about
>> this…..what absorption rate is necessary for functionally food safe
>> pots?  ( continental clays B clay, Buff etc…. )
>> I have always fired these clays to cone 10 but some people suggest
>> that these clays are suitable for both cone 6 and 10 firings.
>> Thoughts?
>> Vanessa Greene
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