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Four north American ball clays fired to cone 10R, 11 and 10 oxidation

It is amazing now similar different ball clays are. Clearly, soluble salts are an issue with all of them (the brownish scum). These bars are much cleaner on the backsides (since the solubles were left on the surface on the fronts during drying). The drying shrinkages, plasticities and fired maturities are also all remarkably similar.

Thursday 7th November 2019

G2934Y glaze on Standard #112 body at cone 6

Produces an appearance very similar to dolomite-matte-glazed ware fired in cone 10 reduction. The effect would be similar using speckled bodies made by other manufacturers. Pieces made by Tom Friedman.

Thursday 7th November 2019

What has the trust in online recipes come to?

These tests of a recipe called "Strontium Crystal Magic". The potter tried it on different bodies and firings. But instead of producing the magic crystals like the pictures, the surfaces fired totally matte. Reasoning "why would anyone put a recipe on line that does not work", she blamed one of the ... more

Tuesday 5th November 2019

Is it possible to make a thin flat porcelain tile from a plastic pottery body?

Yes. The body is Plainsman M370 (~ 25 silica, 25 feldspar, 30 kaolin, 20 ball clay + talc to tune maturity). It is 3.8 mm thick fired (vs. commercial tiles at 5-7mm). It was rolled (in the plastic state) and dried completely between sheets of plaster board. Bisque and glaze firing were on an alumina ... more

Sunday 27th October 2019

Same body, same glaze, same firing. Why did one crawl?

The body: M370. Glaze: G2934Y (with added green stain). Firing: Cone 6 drop-and-hold. Glazing method: dipping (using tongs). Thickness: The same. The difference: Wall thickness. The one on the right was cast thinner so the glaze took a lot longer to dry (the bisque lacked sufficient absorbency). ... more

Sunday 27th October 2019

Over deflocculated vs. under deflocculated ceramic slurry

The slip on the right has way too much Darvan deflocculant. Because the new recipe substitutes a large-particle kaolin for the original fine-particled material, it only requires about half the amount of Darvan. Underestimating that fact, I put in three-quarters of the amount. The over-deflocculated ... more

Wednesday 23rd October 2019

Kiln Firing Curve Recorder - In Development

So many glazes appear as they do because of the firing schedule (especially the cooling curve). Imagine getting an awesome result out of a kiln and not knowing (or being able to replicate) the exact firing schedule that produced it. This device reads and records the temperature once per minute. It ... more

Wednesday 23rd October 2019

Low fire glaze with the Al2O3 and SiO2 of a cone 6 glaze

Look at how fluid G3879 is at cone 06 even though it has the Al2O3 and SiO2 of a cone 6 (or even cone 10 glaze)! It have found that glazes with lots of boron can tolerate amazingly high levels of Al2O3 and SiO2 and still melt very well. And they create many options to lower thermal expansion that ... more

Wednesday 23rd October 2019

By the magic of delflocculation, this powder will mix into that water and still fit in the container

This is 1100cc of water and 3000 grams of M370-2 casting. Amazingly, it is possible to get all that powder into that little bit of water. And still fit in the container (2250cc) and still produce a very fluid slurry for casting. How is this possible? That water has 11 grams of Darvan 7 deflocculant ... more

Wednesday 23rd October 2019

RedArt Slip vs. Albany Slip vs. Alberta Slip melt flow, coverage comparison

These three melt flows and mugs were fired at cone 6 (using the C6DHSC firing schedule). The recipe is GA6-B (80% slip, 20% Ferro Frit 3195). The center flow and mug (M340) employ original Albany Slip in the recipe. The one on the far left uses an Albany Slip substitute that was developed by ... more

Wednesday 23rd October 2019

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• First of all I'd like to congratulate you for the incredible source of information and Guidelines in your website. We are changing our fast-firing process (cold to cold in 4.5 hours) to a slow-firing process (cold to cold in 24.0 hours) and all our glaze formulas have lost their acid resistant characteristic, after dipping in 24 hrs at Ph1.3.

• Tony, the Boraq II substition for gerstley borate in the formula I sent you a while ago was succesful. Congratulations for figuring out boraq! I've tested Murray's, Gillespie, Laguna, IMCO, and also raw materials such as Cadycal, Ulexite, Colemanite, and the substitutes you recommended in your articles made of several components blended with Cadycal (I referred to these in my previous letter) all with varying degrees of success but only the boraq II produced results that were indistinguishable from GB. This glaze is very sensitive so I consider the test a success. It had to mess with the plasticity with additions of hectorite and ball clay.

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