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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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An example of how much Gerstley Borate LOI can affect a glaze

An example of how much Gerstley Borate LOI can affect a glaze

Fired at cone 6. The samples on the bottom tiles are from ten-gram balls that have melted down. These glazes have the same chemistry, but the one of the left sources its B2O3 from Gerstley Borate (which has a high LOI). The one on the right gets it from a frit. Because the fritted version has less ... more

Wednesday 21st February 2018

Should you throw out the brown water on top of settled glazes?

Should you throw out the brown water on top of settled glazes?

This is water from the top of a glaze that had been sitting for more than a year. Clearly, the solute contains iron. It is being dissolved out of one or more of the white powders in the glaze recipe (often frits). The iron, at least, is a contaminant. This should be thrown out and replaced with ... more

Thursday 8th February 2018

Here is what digitalfire.com looked like in 1997!

Here is what digitalfire.com looked like in 1997!

We already had a large library of educational material (the predecessor of the Digitalfire Reference Library). The Foresight product was the fore-runner to insight-live.com today. And it was free like today. And we were warning people about the importance of safe glazes and understanding the "why" questions about the ceramic process.

Thursday 18th January 2018

Matte cone 6 glazes have identical chemistry but one melts more. Why?

Matte cone 6 glazes have identical chemistry but one melts more. Why?

These are 10 gram balls that we melted on porcelain tiles at cone 4 (top two) and cone 6 (bottom two). They compare the melt fluidity of G2934 (left) and G2934Y (right). The Y version sources its MgO from frit and talc (rather than dolomite). It is a much more fluid melt because the frit is yielding ... more

Thursday 11th January 2018

Cobalt and iron overglazes bleeding into the matte glaze

Cobalt and iron overglazes bleeding into the matte glaze

This is the G2934Y matte base with overglaze decoration fired at cone 6. Although this matte has a high melt fluidity, overglaze decoration can be successful as long as it is not applied too thick and not overfired. But in this case the glaze is thickly applied. Once the critical thickness boundary ... more

Thursday 11th January 2018

The value of a white vitreous engobe over terra cotta at cone 03

The value of a white vitreous engobe over terra cotta at cone 03

At cone 03 many terra cottas will fire quite dense and stoneware-like. The lip of the mug on the left is covered with a vitreous white engobe (L3685U) under the glaze (G1916Q). Red bodies are much stronger at low temperatures, but do not lend themselves well to the bright glaze colors that work so ... more

Thursday 11th January 2018

Why you should not paint pure stain powders over glaze

Why you should not paint pure stain powders over glaze

On the left is a pure blue stain, on the right a green one. Obviously, the green is much more refractory. On the other hand, the green just sits on the surface as a dry, unmelted layer. For this type of work, stains need to be mixed into a glaze-like recipe of compatible chemistry (a medium) to ... more

Thursday 11th January 2018

How to convert a dipping glaze to a brushing glaze

How to convert a dipping glaze to a brushing glaze

I have a jar of testing clear glaze that I mixed myself (10% yellow stain and 2% zircopax added to cone 03 G2931K clear). Commercial glaze producers make their lines of glazes like this. The cost of the dry materials: About $6. How can I convert it to a paintable glaze like the commercial ones? I ... more

Saturday 6th January 2018

I have 161 grams of stain. I need to mix it into how much clear glaze slurry?

I have 161 grams of stain. I need to mix it into how much clear glaze slurry?

Stain powders are expensive. I want to make as much glaze as I can from every gram of this red stain I have at hand. I have weighed a teaspoon of my clear glaze liquid slurry (recipe G2926B). I dried it out under a heat lamp and weighed it again (top left). I have filled those two weights, 8.9 and ... more

Friday 5th January 2018

The language of art will never adequately describe this issue or its solution

The language of art will never adequately describe this issue or its solution

This is crazing. It is bad on functional ware. Shivering and leaching are also bad. And blistering. And other problems like devitrification and clouding compromise the visual appearance of ware. Science is needed to understand what these are, how serious they are and determine the cause and ... more

Monday 1st January 2018

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Chemistry plus physics. The on-line successor to desktop Insight. Get an account for as little as $15. It does so much more.

Conquer the Glaze Dragon With Digitalfire Reference info and software

Still available for Mac, PC, Linux

Interactive glaze chemistry calculations.


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