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Conquer the Glaze Dragon With Digitalfire INSIGHT Glaze Chemistry Software

Install it on your PC

This software is focused on ceramic glaze chemistry calculations. Desktop Insight is an application that you download and install on Windows, Linux and Macintosh computers. It is powered by SQLite, the best cross platform database. An Insight-Live account is included free when you purchase Level 2.

Download: Windows (2014-8c), OSX (2014-8c), Linux (2014-8c)

Test, Document, Learn, Repeat in your account at

Use it online

Nothing to download or install. Document recipes, materials, testing, firing schedules, and more in your on-line account! Revolutionary! The future! This does the chemistry and the physics. It works on any browser-equipped tablet or smart-phone. And it is available for a low monthly rate (only 3-8 cents a day).

Tony Hansen's Thousand-Post TimeLine

I am the creator of Digitalfire Insight, and I have made hundreds of posts like these on my Facebook page and personal timeline. My posts are like no others, they help you understand your glazes and clay bodies, take control. They are also part of the Digitalfire Reference Database (referenced from one or more articles, glossary entries, materials, oxides, test procedures, etc). Visit and Like my page to get a notification each time I post. Search is coming soon.

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

I poured 4 teaspoons of two glazes onto a board and let them sit for a minute, then inclined the board. The one with Gleason Ball clay (right, much higher in coal and finer particle size) has settled and the water on the top of running off. The one with Old Hickory #5 ball clay has not settled at all and the whole thing is running downward. Below I have begun to sponge them off. Old Hickory No. 1 Glaze Clay is even better than #5 for suspension. The most amazing thing about this: There is only 7% ball clay in the recipe.

See it in context: No. 5 Ball Clay, No. 1 Glaze Ball Clay, Ball Clay, Suspension, Glaze Slurry is Difficult to Use

Friday 27th December 2013

Can you actually throw a Gerstley Borate glaze? Yes!

Worthington Clear is a popular low fire transparent glaze recipe. It has 55% Gerstley Borate (which is quite plastic) plus 30% kaolin. That means you can actually throw it as if it were a clay, in fact it has excellent plasticity! This explains why it gels almost immediately on slurry mixing, dewaters extremely slowly and shrinks and cracks during drying on the ware. Yet countless potters struggle with this recipe. Frits frits are a better source of the B2O3. It is common to see both clay and Gerstley Borate in recipes, often they impart way too much shrinkage and dry very slowly. A quick fix is to substitute all or part of the raw kaolin for calcined kaolin.

See it in context: Gerstley Borate, Glaze Gelling, Frit

Tuesday 18th March 2014

Yikes, the glaze on the right is going on way too thick and drying too fast

Sometimes EP Kaolin is the best suspender in a glaze, sometimes it isn't. These are the same 85% fritted glaze. A (left) employs 15% Old Hickory #5 ball clay to suspend it, B (right) has 15% EPK. B settles quickly, demands low water content or it runs like water, it goes on very thick even if dipped quickly, it dries instantly and creates uneven thicknesses. By contrast, A goes on like silk, doesn't settle, dries evenly in about 10 seconds. What a difference! All simply because of using a different clay to suspend it.

See it in context: Suspension

Tuesday 25th March 2014

What is the problem here? How can you fix it?

An example of how a glaze that contains too much plastic clay can go on too thick, shrink and crack during drying. This is raw Alberta Slip. To solve this problem you need to tune a mix of raw and calcine material. Enough raw is needed to suspend the slurry and dry it to a hard surface, but enough calcine is needed to keep the shrinkage low enough that this cracking does not happen. If this were fired the glaze would likely crawl.

See it in context: Alberta Slip, Alberta Slip Calcined, Crawling, Glaze Shrinkage, Subsituting Gerstley Borate in Floating Blue, Powdering, Cracking and Settling Glazes

Wednesday 25th July 2012

Are we collectively losing the simple ability to weight out a glaze

Prepared glazes are really starting to hurt our control, independence and sense of responsibility regarding the glazes we put on our ware. We are even losing simple abilities, concepts. Many potters are unaware of even what weighing out a glaze is. Or how to recalculate the total. What the materials are for. Is this a trend we want?

See it in context: What is the Glaze Dragon?

Wednesday 1st October 2014

Double-slip layer incised decoration

An example of a white engobe (L3685T) applied over a red clay body (L3724F), then a red engobe (also L3724F) applied over the white. The incised design reveals the white inter-layer. This is a tricky procedure, you have to make sure the two slips are well fitted to the body, have a compatible drying shrinkage, firing shrinkage, thermal expansion and quartz inversion behavior.

See it in context: L3724F - Cone 03 Terra Cotta Stoneware, L3685T - Cone 03 Opaque White Engobe, Engobe

Wednesday 1st October 2014

Shivering on a transparent over an engobe

Example of a glaze shivering on the rim of a mug. But the situation is not as it might appear. This is a low quartz cone 03 vitreous red body having a lower-than-typical thermal expansion. The white slip (or engobe) has a moderate amount of quartz and is thus put under some compression by the body.But the compression is not enough to shiver off (e.g. at the rim) when by itself. However the covering glaze has an even lower expansion exerts added compression on the slip and therefore causes a failure at the slip-body interface.

See it in context: Quartz Inversion, Engobe, Glaze Shivering

Tuesday 29th July 2014

Cutlery marking is directly related to the chemistry of the glaze

This is an example of cutlery marking in a cone 10 silky matte glaze lacking Al2O3, SiO2 and having too much MgO. This is an excellent demonstration of how imbalance in chemistry has real consequences. It is certainly possible to make a dolomite matte high temperature glaze that will not do this (G2571A is an example).

See it in context: G2571A - Cone 10 Silky Magnesia Dolomite Matte, Cutlery Marking, Ceramic Chemistry, Glaze Chemistry, Predicting Ceramic Glaze Durability by Chemistry

Monday 3rd March 2014

How can you test if a different brand of tin oxide will work?

This is a melt fluidity test comparing two different tin oxides in a cone 6 transparent glaze (Perkins Clear 2). The length, character and color of the flow provide an excellent indication of how similar they are.

See it in context: G2926B - Plainsman Cone 6 M370 Glossy Transparent Liner, A Low Cost Tester of Glaze Melt Fluidity, Improving Cone 6 Perkins Studio Clear

Thursday 13th February 2014

A flow tester has revealed the problem with this glaze

The glaze is cutlery marking (therefore lacking hardness). Why? Notice how severely it runs on a flow tester (even melting out holes in a firebrick). Yet it does not run on the cups when fired at the same temperature (cone 10)! Glazes run like this when they lack SiO2 and Al2O3. The SiO2 is the glass builder and the Al2O3 gives the melt body and stability. Al2O3 also imparts hardness to the fired glass. No wonder it is cutlery marking. Will it also leach? Very likely.

See it in context: A Low Cost Tester of Glaze Melt Fluidity, Cutlery Marking, Fluidity, Melt Fluidity

Friday 22nd July 2011

The difference between dolomite and calcium carbonate in a glaze

These glaze cones are fired at cone 6 and have the same recipe: 20 Frit 3134, 21 EP Kaolin, 27 calcium carbonate, 32 silica. The difference: The one on the left uses dolomite instead of calcium carbonate. Notice how the MgO from the dolomite completely mattes the surface whereas the CaO from the calcium carbonate produces a brilliant gloss.

See it in context: Gerstley Borate, Calcium Carbonate, Dolomite, MgO, CaO, Dolomite Matte

Wednesday 5th March 2014

Exporting insight-live recipes to a CSV file

An Insight-live page displaying four cone 6 matte recipes. It has been exported to a CSV file which I have opened in my spreadsheet software. I then reorganized it to compare these 4 glazes and relate the chemistry to the melt flow tests.

See it in context: The Right Chemistry for a Cone 6 MgO Matte, Ceramic Chemistry, Glaze Chemistry

Tuesday 25th March 2014

A matte and a glossy liner glaze

Left: Ravenscrag G2928C matte on inside of mug. Right: A clear glossy. The matte needs to be soaked in the kiln long enough to make sure it develops a functional surface, especially on the bottom. Mattes are not always the best choice for food surfaces, but you can do it if you blend in enough glossy glaze to make it smooth enough not to cutlery mark.

See it in context: G2928C - Ravenscrag Silky Matte for Cone 6

Tuesday 30th September 2014

The firing volatility of terra cotta clays

These are made from L3724F, an attempt to create a low fire stoneware. The center one is fired at cone 03, the white slip and covering glaze look good. The outer two are fired at cone 02. Suddenly the glaze is blistering inside and out! This demonstrates the volatility of terra cotta bodies. That center piece still has a porosity of 3%, it needs to be a little lower to be stoneware. But to lower it requires a higher firing or more frit in the body, both cause this blistering. Thus, it is better to flux a white body to create a stoneware at low fire. While more frit is needed, it does not have to volatility of a terra cotta.

See it in context: L3724F - Cone 03 Terra Cotta Stoneware

Tuesday 30th September 2014

A vitreous terra cotta slip over a white low fire stoneware

L3724F fluxed terra cotta slip applied over a white burning stoneware (L3685R) fired at cone 03. Most slips in use are not adequately fluxed and do not adhere well to the body below. The frit in this one attaches much better and even enables it to develop a sheen. Also, because of its volatility of color in the cone 03 range, variations in the shade and degree of sheen will impart an appearance like flashing.

See it in context: L3724F - Cone 03 Terra Cotta Stoneware, L3685T - Cone 03 Opaque White Engobe

Tuesday 30th September 2014

One small pinhole in a terra cotta mug and we have a problem

This is L3724E terra cotta stoneware. The inside slip is L3685S, a frit fluxed engobe designed to be much harder and attach better to the body below. The glaze (G1916Q) is Frit 3195, Frit 3110 and 15% ball clay. The body has about 3% porosity, enough to make very strong pots. However that porosity also absorbs water (and coffee). Although not too visible here, the pinhole in the inner surface has enabled absorption and there is a quarter-sized area of discoloration below the glaze. If this piece were fired one cone higher it would be sufficiently vitreous to prevent this, but the glaze would be full of blisters because the body suddenly overfires, starting decomposition within that generates alot of gases.

See it in context: L3724F - Cone 03 Terra Cotta Stoneware, L3685T - Cone 03 Opaque White Engobe, G1916Q - Low Fire Expansion-Adjustable Transparent, Engobe

Tuesday 30th September 2014

Adding an opacifier can produce cutlery marking!

G2934 cone 6 matte (left) with 10% zircopax (center), 4% tin oxide (right). Although the cutlery marks clean off all of them, clearly the zircopax version has the worst problem and is the most difficult to clean. To make the best possible quality white it is wise to line blend in a glossy glaze to create a compromise between the most matteness possible yet a surface that does not mark or stain.

See it in context: G2934 - Plainsman Cone 6 Dolomite Matte Base, Opacifier, Opacification, Cutlery Marking

Wednesday 2nd April 2014

Now that is a translucent porcelain!

These are two cone 6 transparent glazed porcelain mugs with a light bulb inside. On the left is the porcelainous Plainsman M370 (Laguna BMix 6 would have similar opacity). Right is a zero-porosity New Zealand kaolin based porcelain called Polar Ice (from also)! The secret to making a plastic porcelain this white and translucent is not just the NZ kaolin, but the use of a very expensive plasticizer, VeeGum T, to enable maximizing the feldspar to get the fired maturity.

See it in context: Bone Ash, Formulating a Porcelain, New Zealand Halloysite, Bone China, Translucency

Friday 4th April 2014

Is this your record keeping system?

Keeping your valuable notes like this? Recipes? Test results? Are your pictures lost in a cellphone with no keywords or connections to anything? If you test and develop you need to do things a book cannot do. Like link recipes to each other and other things like pictures and firing schedules. You need to group test recipes in projects, classify them. Calculate chemistry and mix tickets. Research materials. Do keyword searches. Books and binders do not do this. Your account at does!

See it in context: Overview Video

Saturday 20th September 2014

Grog before it is ground. Yes, it is bricks.

Pure grog (brick aggregate) is made by crushing bricks to produce a particulate material that is added to sculpture clay bodies to reduce their drying shrinkage (to reduce drying cracks) and impart texture. Brick manufacturers always have a certain percentage of reject and actually grind the reject bricks and clay together. These are structural high temperature stoneware bricks in a stockpile at Plainsman Clays.

See it in context: Grog

Monday 21st April 2014

These posts are actually pictures referenced on pages in The Digitalfire Reference Database, thousands of pages of explaining things you need to know to formulate, adjust and troubleshoot traditional ceramic bodies and glazes. It is organized as: Oxides, minerals, materials, recipes, articles, glossary, hazards, library, MDTs for INSIGHT, pictures, properties, firing schedules, significant temperatures, tests and troubleshooting. Level 2 desktop INSIGHT and Insight-Live both interact with it.

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Are people thinking about glaze toxicity?

  • I have been doing a LOT of reading and learned of your software through the book Mastering Cone 6 Glazes by John Hesselberth and Ron Roy. It became obvious in my reading about glazes that to glaze a piece and know that it was safe for others use and handling was paramount to me, ... people will always use an object in ways you never imagine:) I also want to know why for everything.
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