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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 incredible plasticity of bentonite. And a lesson it teaches.

The 20cm vase on the left is thrown from what I thought was a very plastic body, I achieved close to the same thickness top-to-bottom (5mm). The one on the right was the same original height, 20cm. But it has dried down to only 18cm high, it shrinks 14% (vs. 6% for the other). The thinnest part of ... more

Monday 17th June 2019

3D Printing the Medalta 66 prototype mug

This took 12 hours! Notice the supports it prints for the handle. These break away after it is done. Of course the surface is not smooth enough to use as a model, but the purpose was to hold it to judge size, wall thickness, handle feel and shape. I will make the molds and jigger templates using the printer also.

Friday 14th June 2019

G3806C with lower thermal expansion

G3806C has been our recommended base recipe for reactive glazes (by the addition of colorants and opacifiers). It excels for copper blues, for example. But its thermal expansion is high enough that it crazes on some bodies (e.g. Plainsman P300). To adjust it (via glaze chemistry) I introduced some ... more

Monday 10th June 2019

Almost final recipe for cone 6 copper blue - G2806B

This is the winner of a five-way cone 6 copper blue glaze comparison that started with my dissatisfaction with Panama blue. When I compared these glazes I did not just eyeball them on a tile. I compared the melt flow, thermal expansion and slurry performance of the bases (without the copper and ... more

Tuesday 4th June 2019

Cone 6 copper glaze works because of the fluid-melting base recipe

This is not just a typical transparent cone 6 glaze with 2% copper carbonate added (and 2.5% tin oxide). 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 ... more

Tuesday 4th June 2019

It is impossible to dry this clay. Yet I did it. How?

These are made from a 50:50 mix of bentonite and ball clay! The drying shrinkage is 14%, more than double that of normal pottery clay. It should be impossible to dry them, the most bentonite bodies can normally tolerate is 5%. Yet notice that the handle joins with the walls are flawless, not even a ... more

Tuesday 28th May 2019

Brushing glazes can go on unevenly for more than one reason

Both of these were glazed by brushing. The inside transparent and white glazes are fairly easy to apply evenly but the bright color on the outside left one certainly is not. The problem is a combination of things. It is difficult to apply it evenly with a brush. It is difficult to get it on thick ... more

Tuesday 28th May 2019

Partially and fully opacified cone 6 G1214Z matte glaze

This is a calcium matte base (as opposed to the magnesia matte G2934). The clay is Plainsman M390. 5% Zircopax was added on the left (normally 10% or more is needed to get full opacity, the partially opaque effect highlight contours well). 5% tin oxide was added to the one on the right (tin is a more effective, albeit expensive opacifier in oxidation). The PLC6DS firing schedule was used.

Tuesday 28th May 2019

4% iron oxide in a clear glaze. Unscreened. The result: Fired specks.

Iron oxide is a very fine powder. Unfortunately it can agglomerate badly and no amount of wet mixing seems to break down the lumps. However putting the glaze through a screen, in this case, 80 mesh, does reduce them in size. Ball milling would remove them completely. Other oxide colorants have this same issue (e.g. cobalt oxide). Stains disperse much better in slurries.

Sunday 26th May 2019

Screened to 80 mesh and feels absolutely smooth, but still speckles in reduction

The reduction was fairly heavy and this piece went to cone 11. The tiny iron stone concretion particles melted vigorously and flowed. This is why clean firing results requires 200 mesh materials!

Wednesday 15th May 2019

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