Tom Anderson's Blog (7)

Clay Body Shopping

For those trying to decipher what all those clay specs are actually relating:

Originally published in February 2019 issue of Ceramics Monthly, pages 66,67, & 68. . Copyright, The American Ceramic Society. Reprinted with permission."

techno file: Clay Body Shopping

Added by Tom Anderson on January 20, 2019 at 5:58pm — No Comments

Critical Firing Temperatures

Critical temperatures.

Here is a list of critical temperatures to consider when selecting a firing schedule. The same can be used to trouble shoot potential glaze and clay defects. They are given in C and F temperatures.

130-140F (55C) (Candling) used to rapid dry green ware to bone dry pieces. Most often used by production potters to meet deadlines. Can cause stress fissures on larger pieces or with certain types of clay.

200-392F (100-200C) atmospheric moisture is…


Added by Tom Anderson on July 31, 2018 at 11:20pm — No Comments

Pin Holes and Bubbling

Several recent posts inquired about pin holing in glazes: and asking if clay was involved. With that, I thought I would share some USB pics from a study I did a couple of years back.

Nep Sy is the flux of choice in most commercial bodies because of the price point; nearly a third less than the cost of potassium spars. However, Nep Sy.contains 14-20% soluble salts that migrate as the clay is drying to a bone dry state.…


Added by Tom Anderson on July 19, 2018 at 6:49pm — No Comments

Clay Tips for Studio Potters

Why aged clay is smoother?


Stoneware in particular changes characteristics over time, but all clays do to some degree. The common thought is because of bacterial growth (fungus/mold, etc. Bacterial growth is a reflection of how much organics is in the clay itself (ball clay primarily). If you are getting a lot of bacterial growth on your clay: it indicates high levels of organics: which means you need to bisq slightly higher, or with a hold to burn them off…


Added by Tom Anderson on December 18, 2016 at 5:12pm — 17 Comments

Stoneware Clay Study

After finishing my porcelain clay study, I have moved on to stoneware bodies. At this point, all I am doing is studying PSD (particle size distribution). Typically commercial stoneware bodies run between 10-20% large particle size ( mesh 30-70). I will not bore you with a photo gallery, but just the difference between 20% hawthorne 35m and 50% hawthorne bond 35m is very revealing. I have seen numerous clay recipes with 40-50% large clay particles in their recipe.…


Added by Tom Anderson on October 22, 2016 at 11:16am — 6 Comments

Porcelain Clay/COE Issues

I have been testing porcelain bodies for nearly two years. Recently I purchased a 1600X lab scope to help me see what I had long suspected.

This first image was taken of the clay/glaze interface: the dark area is glaze (cobalt.) The body has a strong glassy matrix and is fully vitrified: so I had to look further.

In going back over my flux tests in clay…


Added by Tom Anderson on September 20, 2016 at 10:26pm — 17 Comments


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Members have had great things to say about John Britt's new book, Mid-Range Glazes. Click the image to buy from

Purchase Glazes Cone 6 by Michael Bailey, The Potters Book of Glaze Recipes by Emmanuel Cooper, or Making Marks by Robin Hopper, all available at amazon.comMastering Cone 6 Glazes by John Hesselberth & Ron Roy is now out of print.

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American Weigh Black Blade Digital Scale, 1000g X 0.1g $11.08 

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If you just want to spout off, it is best accomplished as a blog posting. If you want to get more guidance and ideas from other members, ask a question as a new discussion topic. In the upper right corner of the lists for both types of posting, you will find an "+Add " button. Clicking it will open an editor where you create your posting. 4/16/2014

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