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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 matteness this glaze develops is dependant on the cooling rate

The matteness this glaze develops is dependant on the cooling rate

This is the G2934Y matte cone 6 recipe with a red stain (Mason 6021). The one on the left was fired using the C6DHSC slow-cool schedule. The one on the right was fired using the drop-and-soak PLC6DS schedule. The only difference in the two schedules is what happens after 2100F on the way down (the ... more

Wednesday 20th March 2019

Transparent and RavenTalc silky matte glazes on black engobe at cone 10R

Transparent and RavenTalc silky matte glazes on black engobe at cone 10R

Clay is Plainsman H450. The L3954N black engobe was applied at leather hard stage (on the insides and partway down the outside). The G1947U clear glossy glaze over it on the inside produces a deep and vibrant hue (left). The inside glaze on the right is GR10-C Ravenscrag silky matte. The outsides are GR10-J Ravenscrag Dolomite matte with a little added cobalt and iron (for blue and brown).

Wednesday 20th March 2019

Difference between oxidation and reduction! GR10-C matte on Plainsman H443

Difference between oxidation and reduction! GR10-C matte on Plainsman H443

Same body, same glaze. Left is cone 10 oxidation, right is cone 10 reduction. What a difference! This is a Ravenscrag-Slip-based recipe on a high-fire iron stoneware. In reduction, the iron oxide in the body and glaze darkens (especially the body) and melts much more. The behavior of the tin oxide opacifier is also much different (having very little opacifying effect in reduction).

Wednesday 20th March 2019

Plainsman iron red clays with rutile blue Alberta Slip glaze

Plainsman iron red clays with rutile blue Alberta Slip glaze

Cone 6 mugs made from Plainsman M350 (left) and M390 dark burning cone 6 bodies. The outside glaze is Alberta-Slip-based GA6-C rutile blue and the inside is GA6-A base (20% frit 3134 and 80% Alberta Slip). That inside glaze is normally glossy transparent amber, but crystallizes to a stunning silky matte when fired using the C6DHSC schedule (cool 100F and soak, slow cool to 1400F).

Wednesday 20th March 2019

Sourcing Li2O from spodumene instead of lithium carbonate

Sourcing Li2O from spodumene instead of lithium carbonate

Lithium carbonate is now incredibly expensive. But I was able to source the Li2O from spodumene instead. Spodumene has a complex chemistry, but the oxides that it contains (other than Li2O) are those common to glazes anyway. Using my account at insight-live.com, I did the calculations and got a ... more

Tuesday 19th March 2019

Here is why quartz is good in clay bodies

Here is why quartz is good in clay bodies

The piece on the left is 65% ball clay and 35% nepheline syenite. The one on the right is 65% kaolin and 35% nepheline syenite. Both fire vitreous at cone 6. But the glaze is crazing on the kaolin and not on the ball clay. This is because the ball clay contains significant quartz, that raises the thermal expansion and that puts the squeeze on the glaze and prevent the crazing.

Tuesday 19th March 2019

Functional ware at low fire! Don't dismiss it just yet.

Functional ware at low fire! Don't dismiss it just yet.

These were only fired at cone 04, but they are durable enough to last some time with normal use. The insides have a transparent glaze (Spectrum 700), it is leadless and completely safe. These are great insulators, they keep coffee warm longer than porcelain or stoneware. The feet are glazed so they ... more

Monday 18th March 2019

Which is better for functional ware? Cone 04? Cone 10 reduction?

Which is better for functional ware? Cone 04? Cone 10 reduction?

Not so fast! Cone 10R ware is only strong if the glaze fits. Fortunately this does. But either one will break if dropped on the floor. The stoneware clay has a porosity of 2.5-3%, the earthenware 12%. But the entire base of the orange one is glazed (it was fired on a three-pointed stilt), and the ... more

Monday 18th March 2019

Cheap Amazon glaze mixer, how does it stack up?

Cheap Amazon glaze mixer, how does it stack up?

Make some adjustments and it is usable. First, it is very quiet and has lots of power. The plastic sliders ride smoothly and provide precise adjustability (but the plastic threads might not last). The vertical shaft is stainless steel and the cast iron base is heavy, sturdy, practical. The ... more

Tuesday 12th March 2019

It's possible to formulate a porcelaineous stoneware with just two materials

It's possible to formulate a porcelaineous stoneware with just two materials

Left: 65% #6Tile kaolin and 35% Nepheline Syenite. It's white but crazes the glaze and has 1% fired porosity (measured in the SHAB test) so it does not have porcelain density. Plasticity is very good. Right: 65% M23 Old Hickory ball clay and 35% Nepheline Syenite. The glaze fits, it has zero ... more

Monday 11th March 2019

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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 (legacy, no longer supported)


What people have said about digitalfire

• Abundant thanks on you how much the huge information and useful for me and for domain of pottery and the academic arts and the students.

• Thank u for your helping researchers .. Thank u for your efforts.

• Tony Hanson is like the person that is always waiting to answer my questions. He is very thoughtful and quick with response. I wish he was my neighbor.

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

• 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.

• So far your site has been a blessing in that I don't feel I have to go anywhere else to get my information, you have it all (at least as far as I can see now) right here in one place. I am new to glaze formulation but not to ceramics. Recently I have had a crazing problem with a certain clay body I am using and as of today I feel confident I can solve it using information on your website. It is I who want to thank you for making such a clear and concise information depository that can be used by all, especially those new to glaze chemistry.

• Your website is phenomenal, I love it to get insight on different oxides. I helps me alot, even though we are pretty specialized.


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What people have said about Insight-Live

• I just wanted to express my appreciation for digital fire. It's an invaluable resource that I've been using since I was 18 years old (more than a decade). Keep up the amazing work.

• My glazes activities are seasonal anyway. In the summer i make pots in winter I think about chemistry and sit at a PC. I looked at your pricing again and it is indeed reasonable.

• It's very impressive work you do. Thanks you for providing it.

• And I want to add - you are doing a magnificent job with your webpage. Just unbelievable amount of work and information you put there. I have learned a lot from your webpage. Thank you.

• Thank you very much for your website, as a amateur Potter I find it an incredibly useful source of information about all kinds of things pottery related and when I'm trying to make glazes for example I will often refer to your website for guidance.

• I discovered your website after trial and failure for 35 years. WOW ! The questions you have answered for me and the knowledge are immeasurable To think I am going to get past the Science and onto the Art makes me near giddy. Your site is amazing. My college age kids are going to be dazzled I did this. Every single college ceramic studio should know about your site. I want to tell them!

• Awesome program you have!


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