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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 and clear and uncrazed glass.

Context: Ferro Frit 3602, Lead Bisilicate Frit, Lead in Ceramic Glazes

Thursday 25th June 2020

Guess how many ceramic supply companies there are in Canada and the US

Examples of home pages of various ceramic supplier companies

Eighty. And all of them have websites. Most of them have online stores. Or at least an online catalog. Companies now realize that customers expect, even demand, online buying. If products are not available online locally, many are buying at other stores (especially on Amazon). But there are big differences in the quality of the sites, and in the buying experience. Some of the smaller companies have the best sites! Many of these stores use similar e-commerce technologies. The most common are WordPress, Shopify, Magento and PHP. Shopify and Magento are full-service e-commerce companies, where all product data must be entered into their systems (that means duplication and issues in inventory and accounting effort). Their systems automatically imply pleasing design. And they cost a lot more. Companies using WordPress install it on their own cloud servers and use a plugin named WooCommerce. They have a greater degree of control and integration (but more technical responsibility and effort, maintenance and learning are also implied). PHP is a programming language, companies using it have complete control over the growth of their sites, but this also requires by far the most technical expertise. Perhaps the biggest challenge these companies face is creating a shopping cart that knows the weight of an order of clay or materials and is able to predict the cost of handling and shipping via common carrier. And offer the buyer a shipment tracking service.

Context: Survey of the 80 ceramic suppliers in North America

Thursday 25th June 2020

Is this your record keeping system?

A messy binder that someone uses to store their glaze recipes

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 organize in a way that 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. Book and binder records do not do this. Your account at does!

Context: How many simultaneous testing projects can you manage at once?, Never do body or glaze testing without code numbers, Overview Video, Digitalfire Insight-Live, Insight-Live, Glaze Recipes

Thursday 25th June 2020

Cone 1 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. The glaze is G3806N (v1) with various stains (at 10% concentrations). That glaze is a fluid-melt for cone 6, but it performs nicely at cone 1. There is no visible crazing and the iron body is stoneware-strength. The firing was only held for 10 minutes at cone 1 (no slow cool), yet the glaze looks very good. These coloured glazes are also much 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). We will know more about this body (its degree of maturity and color across a range of temperatures) soon.

Monday 22nd June 2020

Resurface your plaster bat and make it like new!

A plaster table and a capenter's plane

This plaster slab is about 5 years old. I have used it to dewater many raw clays that contain significant soluble salts. Over time they sealed the surface with a hard scum. That not only made the table slower to dewater slurries but it also significantly slowed down the time it took for water to evaporate out of it. Using this carpenter's plane I removed about half a millimetre. The blade self-sharpened. It took some experimentation to set it at a depth that would effectively remove the hard layer. I thought it would produce grooves and unevenness in the surface, but it did not. Sanding was not necessary. And the first slurry stiffened quickly, like a freshly-poured slab, and there were no bits of plaster in it.

Context: Plaster table

Monday 22nd June 2020

Tune your matte glaze to the degree of matteness you want

G2934 is a popular matte for cone 6 (far left). The mechanism of the matteness is high MgO content (it produces a more pleasant surface that cutlery marks and stains less than other mechanisms such as crystallization or insufficient melting). But what if it is too matte for you? This recipe requires accurate firings, did your kiln really go to cone 6? Proven by a firing cone? If it did, then we need plan B: Add some glossy to shine it up a bit. I fired these ten-gram GBMF test balls of glaze to cone 6 on porcelain tiles, they melted down into nice buttons that display the surface well. Top row proceeding right: 10%, 20%, 30%, 40% G2926B added (100% far right). Bottom: G2916F in the same proportions. The effects are similar but the top one produces a more pebbly surface.

Context: G2934, G2916F, A good matte glaze. A bad matte glaze., A functional matte cone 6 glaze should melt as well as a glossy, Cutlery Marking, Glaze Recipes

Thursday 18th June 2020

Stuck at home with no ceramic supplies? Time to organize!

The binder you used to keep records in. The computer and phone we should use now.

Are your records in a messy binder? You could be using an account at! Move your recipes first, assigning each a code number. Then, in your studio/lab, label every fired sample, bucket, jar, glaze test, bag with the corresponding code number. Put in pictures for each recipe. Enter your firing schedules. Research the solutions to issues you are facing with glazes at the Digitalfire Reference Library (ask us questions using the contact form on each of the thousands of pages there). Then start planning improvements and tests. Choose a recipe you need to improve/evolve, duplicate it, increment the code number, make changes, enter explanatory notes. With this preparation you will hit the ground running back at work.

Context: The New 2020 Digitalfire Reference Library is Here, Insight-Live

Wednesday 17th June 2020

The New 2020 Digitalfire Reference Library is Here

The Digitalfire Reference Library on desktop and smartphone

It has morphed into a webapp, reflexive and menu-driven (based on Twitter Bootstrap). It now employs permanent URLs. And pages have logical, and hierarchical URLs (e.g., It correctly forwards 5000+ old URLs. Terms from the glossary automatically hotlink throughout (as do code-numbers for recipes, tests and firing schedules). The search field in the menu bar is area-specific (or all-area at Still no ads and no tracking. The UI displays from server #1, it calls the database API on #2, the email system on #3, media from #4 and from server #5! So it is super fast, flexible and expandable. There are new areas (e.g. projects, pictures, typecodes). Media displays better. Every page still has a contact form, so you can ask any question anywhere. What till you see what's coming!

Context: Stuck at home with no ceramic supplies? Time to organize!, Digitalfire Insight-Live, INSIGHT Glaze Chemstry Software, Digitalfire Insight, Tony Hansen, Digitalfire Reference Library, Insight-Live

Wednesday 17th June 2020

Bisque temperature can make a big difference with fitting glaze at low fire

Two clear-glazed tiles, one crazed, the other not

This is Plainsman Buffstone with G2931L glaze fired at cone 06. A hotter bisque not only produces a stronger body but also eliminates crazing (these specimens where glaze-fired one month ago). Firing the bisque just one cone hotter has transformed the ceramic into a denser matrix having a higher thermal expansion. That has the power to put the squeeze on the glaze, preventing it from crazing. Hotter bisque temperatures can be problematic as they reduce bisque absorbency (thus lengthening dip and drying time for the glaze slurry). But for low temperature hobby ware this is not as much of a problem since glazes are gummed and dry slowly anyway. They are multi-coated for this reason (these were applied in two coats).

Context: Earthenware

Wednesday 17th June 2020

A frit softens over a wide temperature range

Melt flow tests showing the a frit melting from 1550-1750F, Gerstley Borate from 1600-1625F.

This is unlike some raw materials which often melt suddenly. These melt fluidity tests compare the flow of a boron frit across 200 degrees F. It first starts flowing at 1550F (although it began to turn to a glass at 1500F) and is running off the bottom of the runway by 1750F. The Gerstley Borate, on the other hand, goes from no melting at 1600F to flooding off the bottom by 1650F!

Context: B2O3, Frit Fusibility Test, The Chemistry, Physics and Manufacturing of Glaze Frits, Melting Temperature, Frit, Common frits begin melting

Wednesday 17th June 2020

Contact Us:

Use the contact pages within or outside your account at

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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.

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.

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

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