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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 difference propeller-mixing a glaze can make

The glaze has 5% added titanium dioxide. These were fired at cone 6. The titanium in the one on the left remained agglomerated, it did not disperse in the slurry during hand mixing (the agglomerates can be seen as white particles floating in the glass). On high-speed propller-mixing the effect on ... more

Saturday 20th July 2019

CMC gum solutions can go bad

That is why glazes containing CMC often need a biocide if they are going to be stored for extended periods. We made this one. The gallon jar of Laguna gum solution sitting next to this did not go bad, that means they have added some sort of anti-microbial agent.

Saturday 20th July 2019

This flow tester proves the colorant is not fluxing or bubbling the glaze

These glazes are the same (G3806G), except the one on the right has 3.5% copper carbonate added. Copper is commonly thought to flux glazes, making them melt more. But in this case, the clear base is running just as much as the stained one. And I was suspicious that the micro-bubbles in the glass ... more

Saturday 20th July 2019

This cone 6 black glaze looks glossy until placed beside the cone 04 one

The cone 6 one is on the left, it contains about 25% frit. Both are colored using a black stain. That low fire glaze on the right has a high percentage of frit, likely more than 80%, that is the main reason for the beautiful surface. Frits are really fantastic, and standard practice in industry. ... more

Saturday 20th July 2019

Lemon Leaching Test on a Copper-containing Glaze

This was left for 24 hours. Wrapped in stretch wrap. Then the surface of the glaze was inspected under a lamp to detect any differences between the lemoned and non-lemoned surfaces. Lemons are highly acidic. This glaze passed because the base recipe, G3806N, was methodically developed so that it has plenty of Al2O3 and SiO2 (in the fired chemistry) to build a stable glass.

Saturday 20th July 2019

A glaze and underglaze are flaking off. Why?

At low temperatures glazes are not stuck on nearly as well as for stoneware and porcelain. One of the ways to compromise the bond is to put a layer of refractory material, for example certain underglazes, between the body and glaze. It is kind of like painting something that is dirty, the paint ... more

Monday 8th July 2019

Flow tester tells me if I have overfluxed the glaze

This is important because I am searching for a balance between the degree of melt fluidity of my original crazing glaze but having a thermal expansion to fit my porcelain (this is G3806E and F). With each adjustment to the chemistry to drop the thermal expansion I do a firing to compare the melt ... more

Tuesday 2nd July 2019

An alumina kiln shelf that has cracked during firing

This is due to its inability to withstand thermal gradients across its width. Typical sintered alumina is refractory, but it is not thermal shock resistant like tabular alumina. The inner part of the shelf was being protected from the rising heat because of this heavy, slow-to-rise calcimine vessel ... more

Tuesday 2nd July 2019

Dependable blood red at cone 10R without copper

This is G1947U clear glaze with 8% Mason 6021 red stain added. The one on the right has an additional 2% Zircopax added. The glaze is P700, a Grolleg kaolin porcelain.

Friday 28th June 2019

Our base glazes plus opacifiers on a dark burning body at cone 6

The body is Plainsman M390. These are commonly used base glazes. The top one is an MgO matte, next down is a calcium matte. They behave very differently to these additions. Notice also the difference when titanium dioxide is applied thickly. Tin oxide fires whiter than zircon (e.g. Zircopax). Each ... more

Tuesday 25th June 2019

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What people have said about digitalfire

• This is a excellent site for Ceramic colors and containing very good knowledge for Ceramic coloring agents. Thank to Digitalfire Ceramic Oxides Directory.

• I really enjoy the information you have on your website ... it is the best I have seen on the internet ... I appreciated your help on using and creating slips and adjusting base glazes.

• Thank you for Digital Fire!!! Your site and your program are wonderful, thank you for the resource!!

• First of all, I want you to know what an incredible resource your work has been for me the past several years.

• 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.

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• Thank you for the work you do to improve the work of potters trying to do new things.


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What people have said about Insight-Live

• Hey Tony, thanks so much for developing such a useful software. I have come to digital fire for countless questions I have had with clay and glazes.

• Thanks so much this info is so great!!

• Digitalfire is just jaw-droppingly awesome. Thanks for all your hard work.

• As many other users on the web, I want to congratulate you for your amazing digital fire website.

• Yet again, you provide a quick answer not easily found elsewhere (a bowl was befuddling me with wall cracks that never made it to any edges.)

• I am a long time fan. I bought your downloadable book long ago and still refer to it frequently. Has bunches of my notes in it too. It expanded my college training with glaze chem. Appreciate you.

• Thank you so much for this wonderful resource you have created! I have found all of the information in the Digital Fire database as well as Insight to be incredibly helpful tools in the ceramic world.


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