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Tony Hansen
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Chemistry plus physics. Maintain your recipes, test results, firing schedules, pictures, materials, projects, etc. Access your data from any connected device. Import desktop Insight data (and of other products). Group accounts for industry and education. Private accounts for potters. Get started.

Conquer the Glaze Dragon With Digitalfire Reference info and software

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Interactive glaze chemistry for the desktop. Free (no longer in development but still maintained, M1 Mac version now available). Download here or in the Files panel within your Insight-live.com account.


What people have said about Digitalfire

  • I have thoroughly enjoyed the articles on your web site.
  • Great resource!!!
  • Thank you for all your hard work.
  • I regularly use your website for information on many technical aspects of glaze chemistry. I find it extremely useful and thank you for your service.
  • 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.
  • Thanks for your website! I found it greatly informative and useful in my research work on high temperature ceramic materials.
  • I enjoy and appreciate your work very much.
  • However I do believe you have the most comprehensive information anywhere in the world, and I would not hesitate to contact you for any information I required for Ceramic Glaze. I will also refer my associates to you if ever they require assistance.
  • I've become fascinated with Glaze chemistry in the last year or so, have purchased your book, and refer to your site from time to time as well...What a great resource! I have read your book a couple of times, but have not completely digested all of it. I suspect it takes most folks quite a bit of time!
  • I am very thankful that you are so good at what you do! Thank you for all your hard work!

What people have said about Insight-Live

  • You are due many complements on your site and software. I usually have your A - Z materials dictionary open in my web browser.
  • Your website is such a valuable and dependable wealth of knowledge. I’ve had a break from ceramics for a couple of years and have loved that I’ve been able to return to the Insight Live database for my recipes and have read countless articles of yours on glazes. Thank you!
  • Thank you! Tony for all of the impressive work that you have contributed to our industry over the years. Your glaze work has been super helpful.
  • Looking at your website, I have no doubts that there is no other person that would be so dedicated to the subject as you. It is a fact that you have a truly unique knowledge of how things are done, the materials and chemistry being used in such processes. Frankly, I do not complement people and their work easily but you are one of a kind person with some divine dedication to the technology. There are very few people like you and that is a fact. I just spoke with several so-called ceramics, frits and glazes experts and I have to say that they had somewhat limited knowledge while you cover incredibly wide spectrum of all affairs involved in to working with all those great materials.
  • Thanks! I look forward to seeing your posts. I have read and printed many things you have posted over many years. Have learned a lot from you.
  • I have really been enjoying using insight.
  • The knowledge and information you share on digital fire is a rare gem on the internet. I greatly appreciate your writing style. To the point and full of facts. I am wanting to be more active in my glaze creation and begin to make my own glazes. This, to me seems like a huge step away from the safe and what I know of the glazes I have been working with.
  • Thanks for your amazing resources at digital fire. They have been invaluable in understanding clay, as I’m getting started with ceramics. Your emphasis to focus on the chemistry has made the art of ceramic very accessible indeed.
  • It’s been now a couple of weeks that I learn everyday with you and your amazing project. I find your way of tackling experiments clear, practical and smart. I wish more quality content like yours was available on all of my interest topics!
  • Thanks, Your enthusiastic new subscriber.

Monthly Tech-Tip from Tony Hansen

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Blog

Resolution Achieved!

To make this happen, I need goodwill with Plainsman. I know you are passionate about this whole affair in the past few days. I underestimated how much. Some were so passionate they have caused trauma with Plainsman staff, we must undo that. I suggest flowers (only if you can). Having goodwill with the company I partnered with to make Digitalfire is so important and will make me so happy. There were misunderstandings, but these can be forgotten. Here is the biggest one: Digital Fire is not at risk and never was from Plainsman. I need goodwill, especially if you put staff under stress, and you can help me get it. Let's fill their office with hundreds of bouquets of flowers.

Recipient: Plainsman Clays, 671 Industrial Ave SE, Medicine Hat, AB T1A 3L5, 403-527-8535. This is a small town so delivery is easy.

Local shops (all seem to have online ordering and delivery):
https://www.berylsbloomers.ca, https://fresh-flowers.ca, https://www.flowersinmedicinehat.com/

Chain: https://bloomex.ca/florist/medicine-hat
I used this one before I found the local shops. Rats.

Friday 19th June 2026

Please Stop!

Please, everyone, stop bashing Plainsman. It's time for reconciliation.

I should have stated more strongly that this is about helping Digitalfire, not attacking Plainsman. I am very sorry for that. Plainsman Clays is better positioned than any other company in North America because they have their own clay deposits. While this advantage has not been exploited in the past, I sincerely hope the time has come. I want to work with them, not against them.

Friday 19th June 2026

1988 Insight logo reimagined by Gemini

The old logo is from the late 1980s and was used to promote Desktop Insight at trade shows and to advertise it in magazines and later on the early internet. It was done in Aldus Freehand, an early competitor to Adobe Illustrator. Vector graphic illustration was revolutionary at the time. Amazingly, many artists even today do not know what vector graphics is, they are still working with "pixel pusher" apps like Photoshop.

I asked Gemini how it made this, and it said: "I started with a blank canvas of random digital noise (a chaotic grid of pixels) and gradually refined that noise over multiple steps based on your prompt and the layout of your original image. There was not need for a vector stage; the smooth transitions, glowing embers, and soft gradients are baked right into the generation process from the very beginning."

Context: Here is what digitalfire.., Digitalfire Insight

Saturday 13th June 2026

Same body, same outside glaze.

But the inside transparent glaze is different

Glazing black clay bodies stained with manganese is just about impossible with typical transparent glazes. The glaze over-fluxes the clay surface and ruins the color. Worse, if it accelerates surface maturity, the body can blister or generate LOI gases that blister the glaze. How about transparent glazes over a black engobe instead? At least the body color is not lost. But the wrong transparent glaze can do what you see here (inside left).

These mugs are a buff stoneware, Plainsman M340. A black engobe was applied by pouring the inside and dipping the outside two-thirds of the way down.

Left: A L3954F black engobe was applied inside and upper exterior at leather hard. After firing to cone 6 using the PLC6DS schedule, G2926B—which is crystal clear on M340 itself—became completely clouded over the engobe because bubbles generated during firing remained trapped in the melt.

Right: The entire mug was dipped in GA6-B. The Alberta Slip particles and the melt characteristics of GA6-B promote bubble coalescence and escape, producing an exceptionally glossy jet-black surface over the same engobe.

Monday 8th June 2026

Here is what dipping engobes can do:

Go on even. In one coat. Stay put.

When you learn to make and use engobes correctly, they make magic possible. Here I am turning a dark rustic body into a smooth white one (rear mugs) and a white body into a dark one (front). The engobes have been applied at the leather-hard stage. That is the perfect time, the engobe and body are clay bodies, designed to fit each other; they dry together and fire together creating an inseparable bond.

Handles have been applied, and they have dried to stiff leather hard. Engobe was poured in, poured out, then the mugs were pressed, lip down, into it and extracted. No dwell time was needed. This dipping engobe is DIY thixotropic (not available commercially anywhere). That means I tuned it just before use, to just the right degree of gel (enough for it to drain to the right thickness, then gel just as the last few drops fall from the rim). Honestly, these are a beauty to behold at this stage, the silky, drip-free surface is just so perfect.

Context: L3954B, How stop dripping and.., Here s how I.., Why your supplier does.., Why your supplier does..

Monday 8th June 2026

No glaze chemistry needed

At least not right away

You have 147 glaze recipes. How can you get your head around all of them? Is glaze chemistry needed? No, that's a "maybe" way in the future. Right now, you need to start organized documentation. The recipe for each. A few pictures of each fired on different clay bodies, different thicknesses. Perhaps slow and fast-cooled firing. This is what an account at Insight-live does well. What it does even better is tracking your testing. The first step is to assign each recipe a proper code number (replacing these) and write that on all test specimens and buckets. From this point on, learn. Record every observation you make about each in its notes.

Through all of this, constant use in the studio (or factory) will never stop surfacing problems (e.g. settling in the bucket, crazing, running, blistering, material issues, etc.). The seriousness of each will determine the level of attack. First, identify the mechanism of the desired fired result. If it is a base recipe plus additions of colorants, opacifiers or variegators, then check if the base of one of the other glazes has a similar surface texture and character. If so, then could the additives in the troublesome one be used with the better base? If not, then it's time to sanity check the recipe and bring out the heavy guns of at least looking at the chemistry. But in Insight-live, you only need to turn on the display of the unity formula (there is nothing else to do). Next, make sure each material in the recipe links to one in the material database (so the calculated formula is accurate). Then compare the calculated unity formula with a limit formula (often a simple sanity check, like with the recipe, quickly spots oxides that are in excess or are short.

Thursday 4th June 2026

A transparent glaze is going satin:

Is it the feldspar and kaolin substitutions?

A potter reports that a switch from G-200 feldspar to Mahavir, and EPK to Imerys kaolin, has resulted in this transparent glaze becoming more satin. Is that possible? Yes. Because this glaze is on a unity formula tipping point.

To see it, you do not need to know how to do glaze chemistry, just how to display the calculated unity formulas side-by-side. My Insight-live shows them here. The material change has little effect. But there is an anomaly: 0.29 MgO. That is magnesia matte territory. The MgO is very likely there to help bring the thermal expansion as low as possible (to avoid crazing). For people who cool their kilns relatively quickly, this fires glossy. But a material change could well affect the cooling rate needed to maintain the gloss. That being said, the potter may also be firing slower, yet attributing the mattness to the materials. Or it could be a combination of both.

This is a popular glaze, among others in the book "Mastering Glazes". In Ron Roy's circumstances, and for many others, it is glossy. But for this potter, a small change (in the recipe materials and also likely in firing) has produced this issue.

Context: MGBase3, Tipping point

Thursday 4th June 2026

Alberta Slip as a functional honey-transparent base:

The glaze I reach for again and again

The functional surfaces on these pieces all employ the GA6-B base honey glaze recipe. On Plainsman native stoneware clays, especially darker burning ones, typical transparents are very prone to micro-bubble and clouding issues. But not this glaze. The likely reason is that Alberta Slip contains coarser particles (it is only processed to 42 mesh), these act as a fining agent.

This glaze brings multiple other benefits:
-It fits Plainsman bodies, all of them.
-It is made from materials mined in Canada.
-The Alberta Slip base produces a thixotropic slurry.
-It acts as a very good base for dark colors and black.

The top mugs are GA6-B inside and out (MNS clay body). The top right has a black engobe under it.
Bottom left: GA6-B inside, GA6-C outside (MNS and Coffee Clay)
Bottom right: L4768E Coffee casting and M340 casting.

Context: This GA6-B glaze is..

Thursday 4th June 2026

Are glazes food safe just because they carry a label?

This Gemini-generated mug could conceivably exist yet carry these labels. Yet experienced ceramic technicians would immediately be suspicious. The glaze is highly fluid and heavily crystallized; both suggest low or very low Al2O3 levels (it is the key oxide that makes glazes durable). If the interior color were produced using a cadmium-containing encapsulated stain, cadmium-release testing would be essential before claiming the ware is food safe. This is clearly engineered for visual effects rather than durability. None of those characteristics prove it is unsafe, but they do mean that labels like "nontoxic" are not substitutes for actual leach testing. A glaze can be made entirely from materials classified as nontoxic and still fail to meet the durability standards expected of functional foodware.

Context: Commercial glazes on decorative.., ASTM D-4236 - Standard..

Thursday 4th June 2026

Should I glaze the outside of this mug now? No!

This bisque mug has been glazed on the inside. But the bisque has absorbed water from that glaze, and this thin-walled mug is now waterlogged as a result (except at the thicker base). It does not have the absorbency needed to build up a thick enough layer of glaze on the outside. Even if it did, the water from the two glazes would wet the bisque so much that its drying time would be greatly extended. This is a problem because the mechanism of attachment of glaze to the body is fragile and works best when the glaze dries quickly. When drying is too very slow, bubbling and cracking often occur (leading to crawling in the firing).

Context: Does bisque ware need.., Glaze thickness

Monday 1st June 2026



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