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Tony Hansen's Thousand-Post TimeLine

I am the creator of Digitalfire Insight, the Digitalfire Reference Database and ... more


Cone 6 rutile floating blue effect lost. Then regained.

Left: What GA6-C Alberta Slip rutile blue used to look like. Middle: When it started firing wrong, the color was almost completely lost. Right: The rutile effect is back with a vengeance! What was the problem? We were adjusting firing schedules over time to find ways to reduce pinholing in other ... more

Thursday 20th October 2016

Rutile blue glaze effect completely lost! A temporary solution.

Left: 4% rutile in the Alberta Slip:frit 80:20 base. This glaze has been reliable for years. But suddenly it began firing like the center mug! Three 5 gallon buckets of glaze (of differing ages) all changed at once. We tried every combination of thickness, firing schedule, clay body, ventilation, ... more

Thursday 20th October 2016

Underglazes, engobe, a good transparent glaze and cone 03. Life is good!

The white engobe was applied by pouring at leather hard stage. The underglazes were also painted on at leather hard. The mugs were then dried, cleaned, bisque fired, dipping in clear glaze and final fired to cone 03. The clay and engobe have frit additions to make them vitrify at low temperatures.

Thursday 20th October 2016

Blistering in a cone 6 white variegated glaze. Why?

This glaze creates the opaque-with-clear effect shown (at cone 7R) because it has a highly fluid melt that thins it on contours. It is over fired. On purpose. That comes with consequences. Look at the recipe, it has no clay at all! Clay supplies Al2O3 to glaze melts, it stabilizes it against running ... more

Thursday 20th October 2016

Does it matter which transparent glaze you use over underglazes? Yes.

These porcelain mugs were decorated with the same underglazes (applied at leather hard), then bisque fired, dipped in clear glaze and fired to cone 6. While the G2926B clear glaze (left) is a durable and a great super glossy transparent for general use, its melt fluidity is not enough to clear the ... more

Thursday 20th October 2016

Laguna B-Mix on Steroids! I have wedged in 10% and 20% Plainsman P.E.S.

Both pieces have a transparent glaze, G1947U. The bar in the front is PES (Performance Enhancing Substance)! PES is made from 50:50 Plainsman A1 and St. Rose Red, it behaves like a red fireclay. BMix has some specks anyway, so why not concentrate them into some awesome aesthetics? The addition does ... more

Wednesday 19th October 2016

The silica pants of this cone 10R mug have fallen down!

This stoneware mug was glazed inside and halfway down the outside with pure silica. At some point during heatup the outside layer, not shrinking like the piece, simply fell down. And was sintered enough to hang together and remain intact through the rest of the firing (on the inside, the shrinking ... more

Wednesday 19th October 2016

Custer feldspar and nepheline syenite applied pure as a glazes. How?

The coverage is perfectly even on both. The Custer is thicker. How did I do this? Epsom salts. I slurried the two powders in water until the flow was like heavy cream. Then I added a little water to thin and started adding the epsom salts. After only a pinch or two they both gelled. Then I added ... more

Monday 17th October 2016

Pure Custer Feldspar and Nepheline Syenite on cone 10R porcelain bodies

These were applied to the bisque as a slurry (suspended by gelling with epsom salts). The nepheline is thicker. Notice the crazing. This is what feldspars do. Why? Because they are high in K2O and Na2O, these oxides have by far the highest thermal expansions. So if a glaze is high in feldspar it should be no surprise that it is going to craze also.

Monday 17th October 2016

Bamboo glaze that is actually functional

The stunning cone 10R Ravenscrag bamboo glaze (GR10-J plus 0.5% iron oxide) on a Grolleg porcelain. Up close it can feel and look like a fine wood surface (when used on a porcelain). The cone 10 recipes page at has more info.

Monday 17th October 2016

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What people have said about digitalfire

• I am very much appreciative of the work you are doing.

• I want to also thank you for all you have done for the ceramic and pottery industry.

• Thanks a lot for this sea of knowledge.

• I have visited your website for many years to get ceramic information - your website is excellent ... Thanks again for all the great info on your website - hopefully one day I can repay you for your outstanding resourse.

• I have read just about all your articles on Digitalfire and use your software, really appreciate the wealth of knowledge and testing you bring to ceramics.

• Again, thanks for building a website that has been very influential in how I look at ceramics in general, and that has been such a valuable resource to my work as a student, production potter, and chemist.

• I have been studying your web site and which I have found extremely helpful for someone like me who is not a chemist!

• I used Boraq 3 as I wanted the layered action and for the first time, I GOT IT. Thrilled is an understatement. I used the boraq 3 formula in the floating blue receipe and it's wonderful!!!!! My 2000 gram test was encouraging and the 4500 gram test looks great. I've glazed only a few test pieces with larger ones going in later this week. Right now I am one happy campette.

• I have been working as research assistant for the design of continous type microwave dryer for ceramics. Thank you for the infomation provided.

• Hi Tony, First, your website is the most knowledgeable and accurate information available on the internet today. THANK-YOU!

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