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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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High LOI materials can turn your glaze into Aero chocolate!

The smooth surface of this blistering glaze has been ground off to reveal how serious the bubble problem really is. If the body or glaze itself is generating gases of decomposition at the wrong time, and the glaze has too little melt fluidity to pass the bubbles, this can happen. Opacifiers ... more

Thursday 8th August 2019

A runny glaze is blistering on the inside of a large bowl

The glaze is running down on the inside, so it has a high melt fluidity. "High melt fluidity" is another way of saying that it is being over fired to get the visual effect. It is percolating at top temperature (during the temperature-hold period), forming bubbles. There is enough surface tension to ... more

Thursday 8th August 2019

Two batches of EPK tested quite differently in 2018

The kaolin has been mixed 70:30 with nepheline syenite to create a body that matures below cone 6. This enables comparing the degree to which the two kaolins influence vitrification. The darker one is more plastic, has higher drying shrinkage more soluble salts. These dry test bars were fired at ... more

Sunday 4th August 2019

White majolica bases have very, very low melt fluidity

This is Linda Arbuckle's base recipe (66% frit 3124, 23% feldspar, 13 kaolin/bentonite, 9 zircon, 4 tin oxide mixed to 1.62 specific gravity). It is fired at cone 05 creating a super gloss. This is applied very, very thickly (double the thickness of what a stoneware glaze would be). Yet notice how ... more

Wednesday 31st July 2019

For even coverage white majolica glazes must be applied by dipping

The mug on the left has three coats of Spectrum majolica base, painted on by brush from a pint jar. Drying was required after doing the inside coats, so the total glazing time was several hours. The glaze layer is way too thin and it is not even at all! The one on the right was dipped in a 5 gallon ... more

Wednesday 31st July 2019

BEWARE of leaving outsides of functional ware unglazed

This mug is made from the strongest porcelain I have, it is so vitreous that the bare fired surface does not even coffee-stain. So I glazed it only on the inside. That created a time-bomb waiting for hot coffee! Three others did exactly the same. Four other mugs glazed on the outside were fine. Why? ... more

Wednesday 24th July 2019

What is the temperature difference between these two cones?

Four degrees F. I was consistently getting the cone on the left using a custom programmed firing schedule to 2204F. However Orton recommends that the tip of the self supporting cone should be even with the top of the base, not the bottom. So I changed the temperature to 2200F and got the cone on the right.

Wednesday 24th July 2019

Cone 6 Fluid-Melt Transparent Glaze - Jackpot!

In 2015 we did a project comparing common cone 6 fluid-melt base glazes, picked a favourite (Panama Blue) and fixed it's slurry issues and crazing. Fluid-melts almost run off ware when applied thick, but they host stains & opacifiers to produce super-gloss, super-brights. That recipe, G3806C, has ... more

Monday 22nd July 2019

Sourcing Li2O from spodumene instead of lithium carbonate

Lithium carbonate is now incredibly expensive. The glaze on the left employs it. But I was able to source the Li2O from spodumene instead. Spodumene has a complex chemistry, but the oxides that it contains (other than Li2O) are those common to glazes anyway. Using my account at insight-live.com, I ... more

Monday 22nd July 2019

Tin Oxide is expensive, do not waste it by not mixing well

This is a cone 04 glaze on a terra cotta body. Two 300-gram test batches were made. Both have 5% tin oxide added. The one on the left was high-speed propeller-mixed for 10 seconds on a closed container. That was not enough, small agglomerates appear as white specks floating in the glass. The one on ... more

Saturday 20th July 2019

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