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Tony Hansen's Thousand-Post TimeLine

I am the creator of Digitalfire Insight, the Digitalfire Reference Database and ... more


Why does this glaze look like this? What are its mechanisms?

This is cone 6 an oxidation transparent glaze having enough flux (from a boron frit or Gerstley Borate) to make it melt very well, that is why it is running. Iron oxide has been added (around 5%) producing this transparent amber effect. Darker coloration occurs where the glaze has run thicker. These ... more

Thursday 28th July 2016

How do you turn a transparent glaze into a white?

Right: Ravenscrag GR6-A transparent base glaze. Left: It has been opacified (turned opaque) by adding 10% Zircopax. This opacification mechanism can be transplanted into almost any transparent glaze. It can also be employed in colored transparents, it will convert their coloration to a pastel shade, ... more

Thursday 28th July 2016

Recipes without documentation. What is that about?

We find many body and glaze recipes on the internet. These almost always just sit there, taking screen space, not explaining themselves in any way. This is a flameware, made from a recipe promoted by a popular website. Are they serious? How could you throw this? Maybe it is possible, but we need an ... more

Thursday 28th July 2016

Stoneware mug endures thermal shock better than kaolin or ball clay

These are fired at cone 10R. The kaolin bowl on the left survived 2 seconds! The ball clay next to it: 4 seconds. The Helmer clay (halloysite/kaolin) next to that: 8 seconds. The white stoneware piece: 14 seconds. A commercial stoneware mug could survive for 50 seconds or better. Thermal shock ... more

Thursday 28th July 2016

A flameware body being tested for thermal shock. Is this a joke?

A recommended flameware recipe from a respected website (equal parts of 35 mesh grog, talc and ball clay). Looks good on paper but mix it up for a surprise. The texture is ridiculously coarse. Recipes like this often employ fire clays and ball clays, but these have high quartz contents (in a test ... more

Thursday 28th July 2016

This much grog was with that much clay!

This is a sculpture body named Industrial Crank from Potclays in the UK. I dried some out, slurried and screened the grog out then dewatered the remaining clay to get this. There is almost 50% grog. Yet this body is known for amazing plasticity and toughness. How is that possible with this much ... more

Thursday 28th July 2016

How different a ball clay and kaolin can be

These test bars are fired at cone 10R. The top one is EP Kaolin, the bottom one is Old Hickory M23 Ball Clay (these materials are typical of their respective types). It is interesting that although the kaolin has a much larger ultimate particle size it is shrinking alot more (23% vs. 14%). This is ... more

Wednesday 27th July 2016

A novel way to compare degree of porcelain vitrification

These two unglazed porcelain tiles appear to have a similar degree of vitrification, but do they? I have stained both with a black marker pen and then cleaned it off using acetone. Clearly the one on the right has removed better, that means the surface is more dense, it is more vitreous. In industry ... more

Wednesday 20th July 2016

G3806C Transparent with Copper Oxide at cone 6

This is not just a typical transparent cone 6 glaze with copper added. Knowing what is different about this clear base, its trade-offs and how it was developed are important. The porcelains are Plainsman P300 and M370. The liner glossy glaze is G2926B, it has a much lower melt fluidity than the ... more

Tuesday 19th July 2016

A sculpture bodies gets a lot more interesting surface

This is an example of how soluble salts can enhance the appearance of the fired surface of a cone 10R clay. This sculpture body is a vitreous dark brown burning base having lighter colored 20 mesh grog particles. The one on the left uses native stoneware clays that contain natural flux-containing ... more

Tuesday 19th July 2016

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