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Tony Hansen's Thousand-Post TimeLine

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

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Tin oxide can stop the rutile variegation effect dead in its tracks!

This is Alberta Slip (GA6C) on the left. Added frit is melting the Alberta Slip clay to it flows well at cone 6 and added rutile is creating the blue variegated effect (in the absence of expensive cobalt). However GA6D (right) is the same glaze with added Tin Oxide. The tin completely immobilizes the rutile blue effect, it brings out the color of the iron (from the rutile and the body).

Friday 19th August 2016

The classic cone 6 floating blue? No, it is Alberta Slip blue.

And it contains no cobalt! Fairly close in appearance to the classic cone 6 floating blue recipe used across North America, this is a variation of the Alberta Slip Rutile Blue glaze (except this adds 1% tin oxide, 1% black copper oxide and 2% ceramic rutile, it is GA6-C1). Because of the melt ... more

Friday 19th August 2016

How can you make Ravenscrag Floating Blue dance more?

Here it is fired to cone 8 where the melt obviously has much more fluidity! The photo does not do justice to the variegation and crystallization happening on this surface. Of course it is running alot more, so caution will be needed.

Friday 19th August 2016

Want to make a cone 10R super translucent porcelain? Think again.

On the right is a porcelain used in China, renowned for its whiteness and translucency. On the left is a body made from Grolleg kaolin, this is commonly used by potters. They were fired in reduction. The tiny iron specks that potters do not even notice are enemy number for the blue-white porcelain ... more

Friday 19th August 2016

Slow cooling vs. fast cooling on a cone 6 transparent glaze

These are the inside uppers on two mugs made from the same clay with the same clear glaze. The one on the left was fired in a large electric kiln full of ware (thus it cooled relatively slowly). The one on the right was in a test kiln and was cooled rapidly. This glaze contains 40% Ferro Frit 3134 ... more

Friday 19th August 2016

EPK fired bar (top) vs Grolleg at cone 10R. Why shrinking more?

EPK has a much higher fired shrinkage. This is counter intuitive because Grolleg is known to produce more vitrified porcelains. It also appears whiter yet in a porcelain body the Grolleg will produce a much whiter fired product. This means that to compare porcelains we need to see them "playing on ... more

Saturday 13th August 2016

Thermal shock failure in raw ball clay much worse than the 100 mesh material

The cup on the left is raw, unground, ball clay (Plainsman A2 fired to cone 10 reduction). It cracked under a flame in only 4 seconds. The 200 mesh version on the right lasted 14 seconds (it is broken because I dropped it). It would appear that the larger quartz particles in the material on the left are imparting much less resistance to thermal shock failure.

Saturday 13th August 2016

The difference in fired character between kaolin and ball clay is not what you might expect

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

Saturday 13th August 2016

Two transparent glazes on the same dark burning clay. Why different?

These two glazes are both brilliant glass-like super-transparents. But on this high-iron stoneware only one is working. Why? G3806C (on the outside of the piece on the left) melts more, it is fluid and much more runny. This melt fluidity gives it the capacity to pass the micro-bubbles generated by ... more

Friday 12th August 2016

Tune your matte glaze to the degree of matteness you want

G2934 is a popular matte for cone 6 (far left). It is not matte because it is not melting enough or is covered with micro-crystals, it is an MgO matte (a mechanism produces a more pleasant surface that cutlery marks and stains less). But what if it is too matte for you? This recipe requires accurate ... more

Thursday 11th August 2016

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