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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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Low fire nirvana: Use commercial underglazes but make your own clear over glaze

Low fire nirvana: Use commercial underglazes but make your own clear over glaze

Decorate ware with the underglazes at the leather hard stage, dry and bisque fire it and then dip-glaze in a transparent that you make yourself (and thus control). These mugs are fired at cone 03. All have the same transparent glaze (G2931K), all were decorated with the same underglazes. Notice how ... more

Sunday 17th September 2017

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

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.

Sunday 17th September 2017

Glaze melt fluidity comparison between G2931F and fritted G2931K show the effect of LOI

Glaze melt fluidity comparison between G2931F and fritted G2931K show the effect of LOI

These two glazes have the same chemistry but different recipes. The F gets its boron from Ulexite, and Ulexite has a high LOI (it generates gases during firing, notice that these gases have affected the downward flow during melting). The frit-based version on the right flows cleanly and contains ... more

Sunday 17th September 2017

Deep, deep blue without any cobalt. How?

Deep, deep blue without any cobalt. How?

These have to be seen to be believed, it is the deepest, richest blue we have ever produced. This is Plainsman M340 fired to cone 6. Black-firing L3954B engobe (having 10% Burnt Umber instead of the normal 10% Zircopax) was applied inside and partway down the outsides (at the stiff leather hard ... more

Sunday 17th September 2017

Dip-glazing vs. brush-on glazing: Which gives the more even surface?

Dip-glazing vs. brush-on glazing: Which gives the more even surface?

This is a clear glaze (G2931K) with 10% purple stain (Mason 6385). The mugs are cone 03 porcelain (Zero3). The mug on the left was dipped (at the bisque stage) into a slurry of the glaze (having an appropriate specific gravity and thixotropy). The glaze dried in seconds. The one on the right was ... more

Wednesday 13th September 2017

The varying power of different encapsulated stains

The varying power of different encapsulated stains

These mugs are fired at cone 03. The outside glazes are G2931K transparent with added stain plus 3% Zircopax. The left one contains 10% Mason 6021 red. The right one has 15% Cerdec 297497 red stain. The latter is an older product, obviously not as potent. Encapsulated stains are a revolution in ceramics but test the ones available. You could save money and get better color at the same time.

Wednesday 13th September 2017

Making ceramic tile shapes by 3D printing your own cookie cutters

Making ceramic tile shapes by 3D printing your own cookie cutters

This was done on an affordable RepRap printer. The shapes were drawn in Illustrator, extruded in Fusion 360 and sliced and printed using Simplify3D (which took about 30 minutes each). The round wooden block was used to press them into the clay. The plastic wrap made sticking a non issue (and rounds ... more

Wednesday 13th September 2017

Printing a prototype propeller for my Lightnin lab mixer

Printing a prototype propeller for my Lightnin lab mixer

An example of how handy the ability to print in 3D can be. The worn-out stainless propeller costs $300 to replace. But the size and pitch of the blades is not ideal for the work I do. I can experiment with different configurations and print them in hard plastic, then have a new stainless one printed ... more

Wednesday 13th September 2017

Original glaze with Gerstley Borate vs. fixed version with frit

Original glaze with Gerstley Borate vs. fixed version with frit

These pieces are the same body and fired at the same temperature. The original glaze was found on the internet, and is popular. Materials within it are "farting" as the glaze is melting (they have a high LOI and the calculated LOI of the glaze as a whole is 15%). Unless it is applied very thinly ... more

Wednesday 13th September 2017

Crazing due to moisture expansion in a porous low fire body

Crazing due to moisture expansion in a porous low fire body

The clear glaze on this cone 03 mug survived a 300F-to-ice-water thermal shock test without crazing. However, in the process, water was absorbed by the bare foot ring and dispersed into the porous matrix of the lower part of the mug. Moisture expansion occurred as a result and produced the crazing. ... more

Wednesday 13th September 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

• I must say that your article on geting pink colors from Chrome and Tin had an appealing writing style and was very informative.

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

• I have used this site on numerous occasions for glaze information and always get a personalized answer, quickly, and plenty of help. They go above and beyond the call of duty!! They are a excellent website for potters!!

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

• 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.

• I have found the glaze information on your site really helpful for quite some time now. I like the way that there is an emphasis on problem solving and understanding how things work, rather than just offering recipes that might work.

• Firstly, I want to thank you about this very good site in the net which helps very much in the development of the ceramics industry.

• Your resources are truly amazing and as an ex electronic engineer (now a potter), I really am impressed with your analytical approaches. Your site is almost a complete college level course on pottery (less the throwing & handbuilding). Thank you for your wonderful contributions.

• if I am unable to find an answer, I can most always depend on this site !!!!! I appreciate your efforts greatly.

• I think Glaze chemistry is an extremely under-appreciated and under-estimated field of science.


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