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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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The covering power of an engobe is amazing. If they are not over-fluxed.

The covering power of an engobe is amazing. If they are not over-fluxed.

This cone 6 mug is made from a black clay (containing 10% burnt umber). The engobe on the inside is covered by a clear glaze. The color is the same as if the engobe were on a white or buff firing stoneware. Engobes get their covering power from the fact that they do not melt. If you see an engobe with lots of frit it will likely melt too much, be suspicious.

Thursday 20th July 2017

Encapsulated stains are firing with a mass of bubbles and pinholes

Encapsulated stains are firing with a mass of bubbles and pinholes

This is happening on five different stains at 8% concentrations. The body: A fritted porcelain. Temperature: Cone 03. The glaze: 85% frit. The solution? Documentation for inclusion frits notes that adding 2-3% zircon can brighten the color. Although this does not seem intuitive, we added 2% anyway ... more

Wednesday 19th July 2017

A terra cotta body fired from cone 06 (bottom) to 4

A terra cotta body fired from cone 06 (bottom) to 4

Terra cotta bodies are more volatile, maturing more rapidly over a narrower range than others. These bars are fired (bottom to top) at cone 06, 04, 03, 02, 2 and 4. This is Plainsman BGP.

Wednesday 19th July 2017

Digitalfire Insight in 1983. On a Macintosh 128K and original IBM PC.

Digitalfire Insight in 1983. On a Macintosh 128K and original IBM PC.

These were the machines that began the computer revolution. Insight was there! It was 12 years before the internet.

Tuesday 18th July 2017

Same glaze, same kiln, same clay: The right one crystallized. Why?

Same glaze, same kiln, same clay: The right one crystallized. Why?

Well, actually they are not exactly the same. This is 80% Alberta Slip and 20% frit. But the frit on the left is Ferro 3195 and on the right is 3134. By comparing the calculated chemistry for these two we can say that the likely reason for the difference is the Al2O3 content. Frit 3134 has almost ... more

Tuesday 18th July 2017

How many porcelain mugs from one box of clay?

How many porcelain mugs from one box of clay?

This is from half a box! 21 mugs from 10 kg ( (all scrap was reclaimed). Polar Ice porcelain double the price of others. Why use it? Because it is so plastic that you can make more pieces, many more, enough to more than pay the extra clay cost. And you can charge more for each piece. These have a ... more

Monday 17th July 2017

Cone 6 copper glazes like this require a special high-melt-fluid base

Cone 6 copper glazes like this require a special high-melt-fluid base

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

Sunday 16th July 2017

Stains added to a glaze can change its melt fluidity

Stains added to a glaze can change its melt fluidity

At the top is a melt-flow ball of a cone 6 satin matte glaze, G2934. Left bottom: 8% 6213 Mason Hemlock Green stain has been added. The percentge appears to be sufficient, but it is not melting as much and the surface is more matte. A solution is too employ a 90:10 or 80:20 matte:glossy glaze blend ... more

Sunday 9th July 2017

If you think one slip fits any body, think again

If you think one slip fits any body, think again

This flake shivered off the rim of a low fire terra cotta mug. It is Fishsauce slip. It is about 2 inches long and has razor sharp edges. This is not the sort of thing you would want to be falling into your coffee or food and then eating! This flake did give evidence that it was loosening so there ... more

Sunday 9th July 2017

Underglazes at low fire are brighter than at medium temperature

Underglazes at low fire are brighter than at medium temperature

Medium temperature transparents do not shed micro bubbles as well, clouds of these can dull the underlying colors. Cone 6 transparents must be applied thicker. The stains used to make the underglazes may be incompatible with the chemistry of the clear glaze (less likely at low fire, reactions are ... more

Sunday 9th July 2017

Test, Document, Learn, Repeat in your account at insight-live.com

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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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What people have said about digitalfire

• We have been aware of your company and website for many years and see it as a model in its approach to educating makers about the processes involved in making/drying/firing. You teach them to take responsibility for their work process rather than blaming the product.

• Your website has been very helpful to me over the past several years. I refer fellow potters to it constantly. Your G1214Z matte glaze formed the basis for the glaze used on my tea bowls.

• Your attention to the people has been allways great, as its your software, thanks for the support.

• I think that I have read almost every article I found on digitalfire.com ... I admire your knowledge about glaze mess, it is very very complicated to me.

• Thanks for the wonderful service.

• Very useful articles on practical solutions to the every day problems Ceramic Technicians face in their organizations.

• Go look at Tony Hansens page and look at Insite. Incredible amounts of information. He has a great explanation of .. Shivering ---and the opposite----- Crazing. Cause and solution.

• Great site you have here, I am the ceramics tech at the University of .. the info. on your site is a great help to my students.

• Thanks a lot for this sea of knowledge.

• I enjoy and appreciate your work very much.


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