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fw: fire clay (is it really so bad)

updated mon 17 jun 02


Ceramic Design Group on sun 16 jun 02

Subject: Re: Fire clay (is it really so bad)

In answer to the question...."Fireclay, is it really so bad?" I would answer
a very positive and loud "YES"!

My history with fireclay bodies dates way back. You can check the Studio
Potter website archives for "Variations in Raw Materials"
( whcih I authored some time ago that chronicled my
purchase of a 40 ton lot of lime contaminated Pine Lake 30 mesh fireclay.

You can also check out in the educational section there is
an article I authored entitled "The Whining Stops Here". This is a piece
detailing how to critically look at your clay bodies and clay materials.

Fireclays are the weak link in potters clay bodies. Given that many of the
fireclays that we use are now no longer on the market, this may be a moot

Seriously, the idea of a fireclay based plastic body or even one that has
any percentage in it will be problematic. If not at the present, at sometime
in the future.

We use a small percentage of Greenstripe fireclay in our stoneware casting
body. The entire wet mix is sieved prior to use. This is the key to
successful use of fireclay bodies. Get rid of the junk. You can't wet sieve
a plastic body unless it is prepared wet, sieved, filter pressed, and then
pugged. Now that Greenstripe is no longer available, I can easily eliminate
this from the mix anyway, its not rocket science. I may have about 1000
pounds of Greenstripe in inventory which should last a while!

I think that using these refractory clays is basing the hard work of your
labor on materials that are at best, risky and have the potential to trash
load after load of your ware. These materials are not made for the ceramic
industry. Why potters use them is beyond me. The idea of tooth, strength,
refractoriness, etc in a body can be achieved using other materials that
are more processed and provide a greater degree of safety. If you want to
make work that has the potential for problems down the line, be my guest,
use as much fireclay as you wish!

We also use some Newman Red clay for color. This is not only screened dry
before it goes into the mix, but we also wet screen it prior. We use a small
amount and there is really no big labor with doing this. And the color is
fine, like the old PBX Valentine Fireclay from New Jersey, years ago!

Our stoneware bodies are resilient, strong, have successful dilitometry, and
work. We have stoneware casting bodies, plastic bodies for pressing,
jiggering, and throwing, all without fireclay. They work for us.



Jonathan Kaplan, president
Ceramic Design Group
PO Box 775112
Steamboat Springs CO 80477
voice and fax 970 879-9139

Plant Location:
1280 13th Street Unit 13
Steamboat Springs CO 80487
(please use this address for all deliveries via UPS, comman carrier, Fed Ex,

"Custom design and manufacturing for the ceramic arts, giftware and pottery
industries. Molds, models, and tooling for slip casting, jiggering and
hydraulic pressing. Consultation on clay and glaze formulation, production
systems,firing, and kilns.