Click here for information about DIGITALFIRE Corporation

Imagine if you had everything for production at home during Covid-19

All the things a potter needs: materials, equipment, supplies, tools

This is what you need to be independent, to create your own manufacturing company in your garage. Some of the prices are "instead of" rather than additive. There are many approaches to glazes, the more you are willing to learn the better you will be able to make your own (and save a lot). We recommend the cone 6 range using a small test kiln (like this 220v ConeArt GX119, don't scrimp on this, go for quality and the practicality of a Genesis controller). A kiln you can fire often and inexpensively is a key enabler to learning, developing techniques, products, designs, durable and decorative surfaces, solving problems. It can be fired multiple times a day. And it is big enough for mugs and similar sizes. It will get you into the habit of using some of your creativity for experimenting. It will give you the successes early on that will inspire you to press on learning. When you are ready, then get a big kiln and hit-the-ground-running. This potter's wheel is the best available and will last a lifetime, these often appreciate in value over time. And, build yourself a good plaster table. You will use it constantly. Not shown here is a propeller mixer, also an important tool. And you will need a sink equipped with a sink trap (Gleco Trap).

Context: Where Do I Start?, Trafficking in Glaze Recipes, Propeller Mixer, Test Kiln

Monday 6th July 2020

Ferro lead alumina bisilicate Frit 3602 melt flow over many temperatures

This demonstrates the amazing melt behaviour of lead-as-a-flux for ceramic glazes. Not only does it melt early, but it softens slowly over a 300F range of temperatures before it goes off the end of the runway on this GLFL test. Then, when fired 200F hotter than that, it remains a stable, clear and uncrazed glass. Beginning around 1750F, this becomes a transparent glaze, by itself.

Context: Ferro Frit 3602, Lead Bisilicate Frit, 1700F Frit Melt-Off: Who is the winner?, Is Mexican Terra-cotta pottery lead-glazed? Yes., Lead in Ceramic Glazes

Saturday 4th July 2020

Is Mexican Terra-cotta pottery lead-glazed? Yes.

A lead-glazed handled cup still common sold in markets in Mexico

This piece was bought in Sinaloa in 2020. The merchant said it was made in Puebla. The lead test procedure involves leaving white vinegar in the piece overnight, pouring some of that into a test tube, dipping a cotton swab into a reagent solution and then stirring the vinegar. The color indicates lead content. As you can see, it has turned black, indicating heavy concentration of lead. This pottery is a tradition in Mexican culture and is used for food and liquid surfaces everywhere. There are manufacturers trying to make stoneware that retains the traditional appearance, but few people use it. Further refiring tests demonstrated that these are fired around 1700-1750F, a temperature sufficient to melt pure lead bisilicate into a glossy transparent but the body is still very soft and porous.

Context: Ferro lead alumina bisilicate Frit 3602 melt flow over many temperatures, Lead Toxicology

Saturday 4th July 2020

1700F Frit Melt-Off: Who is the winner?

Melted balls of 15 frits on a ceramic tile

These were 10g balls melted using our GBMF test. Frit 3602 is lead bisilicate. But it got "smoked" by the Fusion FZ-16 high-zinc, high-boron zero-alumina! Maybe you always thought lead was the best melter. That it produced the most transparent, crystal clear glass. But that is not what we see here.

Context: Fusion Frit FZ-16, Ferro Frit 3602, Glaze Melt Fluidity - Ball Test, Fusion Frit FZ-16-2 melt flow over many temperatures, Ferro lead alumina bisilicate Frit 3602 melt flow over many temperatures

Friday 3rd July 2020

The ball clay you use to suspend your glaze is important!

I poured 4 teaspoons of two glazes onto a non-absorbent butcher’s board and let them sit for a minute, then inclined the board. The one on the right employs Gleason Ball clay, the left one has Old Hickory #5 ball clay. Neither has any slurry property modifier addition. The one on the right has settled and on incline the watery upper is running off. The other has gelled and the whole thing is running downward slowly. Below I have begun to sponge them off, the one on the right is sticky. The most amazing thing about this: This difference appears despite that there is only 7% ball clay in the recipe.

Context: No. 5 Ball Clay, No. 1 Glaze Ball Clay, Ball Clay, Suspension, Glaze Slurry is Difficult to Use or Settling

Friday 3rd July 2020

Fusion Frit FZ-16-2 melt flow over many temperatures

This melt flow tester demonstrates the beautiful crystal-clear glass this zinc frit creates by 1700F. It fits this porcelain without crazing, even though very thick and high in sodium (the high zinc and boron are countering it to keep the thermal expansion down). It runs off the end of the runway around 1600F on this GLFL test, rivaling lead bisilicate. This is a more concentrated boron source than even Gerstley Borate. Everything about this material screams “ultra gloss”, what a material to build a fluid-melt reactive super-glaze on!

Context: Fusion Frit FZ-16, 1700F Frit Melt-Off: Who is the winner?

Friday 3rd July 2020

Form a ceramic glaze into balls? Why would you want to do that?

The process of dewatering a glaze slurry and making balls

The vast majority of glazes are plastic (but less than clay bodies). They can be dewatered on a plaster surface and formed. Why do this? To make 9-10 gram balls and fire them on flat tiles (or inclined flow testers) to see their melting characteristics. It is surprising how much this can tell you about the glaze. To make the ball, mix the slurry well and pour a little on the plaster. It should dewater in less than 30 seconds. As soon as the water sheen is gone, scrape it up with a rubber rib, hand-knead it and flatten it back down to dry a little more if needed (leave it only for five or ten seconds and rework it. Repeat until it is stiff enough to form balls of about 12 grams. Stamp them with ID numbers and dry them.

Context: Glaze Melt Fluidity - Ball Test, A Low Cost Tester of Glaze Melt Fluidity

Thursday 2nd July 2020

Lincoln Fireclay is plastic, it can be thrown on a potters wheel

Two freshly thrown mugs made from pure Lincoln 60 fireclay

The left two were made from a 100% mix of Lincoln 60, the right one adds 2% bentonite (Lincoln 60, by itself, matures into a stoneware at around cone 8). While it was possible to throw the pure material, the plasticity is a little lower than a normal pottery clay. That being said, it is smooth and has a soapy feel that makes it very pleasant to work with. A simple 2% addition of bentonite transformed it into a delight to throw! That only increased the drying shrinkage by about 0.5%.

Context: Lincoln 60 Fireclay

Thursday 2nd July 2020

Cone 1-4 stoneware by mixing a low and medium temperature body

Four tiles of a red-burning clay covered with purple, yellow, orange, black glazes

These tiles are a 50:50 mix of Plainsman L215 and M390. They are fired at cone 1, 2.5 &4 (columns 1,2,3). The glaze is G3806N (v1) with stains at 10% concentrations. That glaze is a fluid-melt for cone 6, but it performs nicely down to cone 1 and even lower. There is no visible crazing and the iron body is stoneware-strength. The firings were only held for 10 minutes at cone (no slow cool). These coloured glazes are also less "muddied" by the iron in the body than would be the case at cone 6. This is a really amazing result. Red-burning bodies can be difficult at cone 6 (if fired too high the red color is lost, if fired too low they are too porous).

Wednesday 1st July 2020

Kiln wash that really works. How?

Two kiln shelves, the wash on one is even and perfect, the other is flaking and falling off

The shelf on the right in the traditional kaolin:silica kiln wash. Flaking constantly. Sticking on the feet of ware. A real aggravation. The one on the left is L4001, it is perfectly even. Yet thin. Much more refractory so it has not hardened or become brittle. Or cracked. And it paints on beautifully. The secret? Zircon. Zircopax, to be precise. Zircopax is among the most refractory materials in ceramics. We mixed it with some calcined, rather than raw kaolin. That greatly reduces drying and firing shrinkage and helps densify and stabilize the coverage (by its flat particle shape). Laguna gum solution was added to harden the dry layer and slow down the drying (their gum solution has a higher percentage of CMC than achievable using common mixing methods). Click the link below to get the recipe.

Context: Plainsman Super Kiln Wash, Kiln Wash

Monday 29th June 2020

Contact Us:

Use the contact pages within or outside your account at

Test, Document, Learn, Repeat in your account at

Login to your online account

Chemistry plus physics. The on-line successor to desktop Insight. Get an account for as little as $15. It does so much more.

Maintain your recipes, test results, firing schedules, pictures, materials, projects, etc. Organizing that data will better empower you to adjust, formulate and fix your recipes and processes. Link, share and publish.

Conquer the Glaze Dragon With Digitalfire Reference info and software

Still available for Mac, PC, Linux

Interactive glaze chemistry calculations. Free and unrestricted (legacy, no longer in development).

What people have said about Digitalfire

  • I would also like to say thank you for providing the information about glaze's that you have on your websight. I have been formulating glaze for 20+ years, read practicaly every book on glaze & glass and your web page's had better information than any book.
  • This article is just what I have been looking for, actually for years. I am going to experiment making my shiny clear glaze matte. I do not have an MFA and have not really ever studied glaze calculation and yet I understand this article and know where to start. Thank you!!!
  • 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.
  • Thanks for sharing so much great information!
  • I'm excited to get started learning how to use the program. I've drawn much from your online glaze chemistry information over the years, and now I hope to apply some of that knowledge effectively.
  • I feel your information about majolica and glaze adaptation is the best I've seen anywhere and I do understand I need to do the testing and find what works for my situation.
  • I would love to take a trip inside of your brain. I am sure that it would be a fantastic light show.

What people have said about Insight-Live

  • Love the post (about leaching in glazes). I am the bad guy on Facebook ceramic because I always bring up this subject. So sad.
  • Extremely useful resource Digital Fire. By the way your writing style is truly unique and is easily understandable even though of technical nature.
  • I want to thank you for creating all that extensive and wonderful material in Digital Fire and Insight Live. I have started with the process of creating my own glazes a little bit more than a year ago, process that I found exciting and challenging and thanks to your websites it has been a lot easier!
  • First, I want to thank you for all the help we got from Digital Fire; thank you very much for this huge work and to share it like that.
  • I have used the digital fire database for years and am beyond grateful for your work.
  • Thanks for sharing your extensive knowlege with the clay community.
  • Your site is amazing and your videos too. Such an inspiration.

DigitalFire Logo

Privacy Policyhi11