For those who reclaim/recycle clay. 

https://ceramicartsnetwork.org/ceramics-monthly/ceramic-supplies/ceramic-raw-materials/techno-file-clay-restoration/

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. http://www.ceramicsmonthly.org . Copyright, The American Ceramic Society. Reprinted with permission."

techno file: Clay Body Shopping

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…

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.…

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…

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.…

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…