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Recognize these universal oxidation glazes?

Almost every potter needs a Albany brown and rutile blue.

Rutile blue and Albany brown glazes

These are made by Barbara Childs Pottery. To keep costs down, they are undoubtedly using dipping glazes that they mix themselves. Although these look like two Potter's Choice glazes, PC-32 Albany Slip Brown and PC-20 Rutile Blue, Amaco did not invent them. Like the others in their product line, they simply drew on readily available pottery glaze recipes. But they didn't just use the recipes; they adapted and improved them. Consider the rutile blue. They are not using the traditional G2826R floating blue recipe, there are new and better ways using recipes like GA6-C and GR6-M. Likewise, with the other, they are not using the traditional G2415E Albany Brown recipe. Rather, they will have improved it (e.g. like I did with G3933G1). They also likely found a way to reduce or remove the lithium to cut costs. Maybe you are a hobbyist and don’t feel you need to DIY your costs down. But do your customers feel the same way? Not buying just ten small jars of brushing glaze will pay for a mixer and much of the ingredients to make gallons of each of these as dipping glazes. It will also set you on the road to gradually improving the glazes you use. And even reducing your prices.

Context: Adding 6 lithium carbonate.., PC-2 floating blue with..

Tuesday 9th September 2025

A draining issue with a slip cast bottle

It is turning inside out!

Slip casting bottle turning inside out

Why did this happen? There is a perfect storm of factors. Draining, during slip casting, creates suction and slip is heavy (1.8 times heavier than water). And this mold is tall with a narrow neck. So that creates a lot of suction. A slip having inadequate fluidity complicates draining. This round shape, even with printing artifacts, also releases well. How can this issue be avoided?

-Draining the mold carefully, holding it near horizontal for much of the drain.
-Use a well-deflocculated slip.
-Add bentonite to the slip, perhaps 0.5%, to make it stickier and slow down release time (which also slows down the casting time).
-At times, this will happen despite all efforts. In that case, if might be necessary to use a tube (e.g. 1/2 or 5/16”) to pump most of the liquid slip out of the bottle before inverting it. Adapt a 3D printed pour spout to keep the tube centered, at least near the mouth of the bottle.

Context: Slip Casting, Beer Bottle Master Mold.., Casting Slip Problems

Saturday 6th September 2025

OnShape CAD is Free for Hobby Makers:

Is it as good as Fusion 360?

It is very hard to let Fusion 360 CAD go. But the approaching $750 renewal is powerful motivation! OnShape is amazing. There is nothing to install, it runs in a browser tab like Google docs (see picture below). Sure, it won’t run offline, but I am almost never offline. It functions very similar to Fusion 360 for my basic requirements of making molds for slip casting. Recent experience with the complexity and slowness of Solidworks for Makers, which is total overkill for what I need, really makes OnShape look good.

My OnShape drawings are stored in my cloud account and are public. That sounded bad at first, but it also means that they are shareable with others (another person, whom I choose, can actually work on a drawing at the same time as me). The full OnShape is working in Firefox on my 2014 Mac Mini Ubuntu Linux machine. This is beyond exciting to me, traditional CAD has always required expensive hardware that is far beyond a hobbyist (of course, OnShape will also work in Safari on Mac and Chrome on Windows). A real bonus: I can edit drawings on iPad in what appears to be full power mode (although a mouse and keyboard are needed for serious work).

Besides the above, here are some of the features and advantages I am seeing:
-It opens and saves many professional CAD file types (a major drawback in SolidWorks for Makers).
-It is really fast, login is quick and a drawing can be open in seconds, this is way better than xDesign for Makers (from Solidworks).
-Documents are always saved, close one by simply clicking the home icon on the upper left.
-The timeline (called the "Feature Tree") can be reordered, turned back and has folders like Fusion 360.
-To 3D print just select part of your drawing, right-click and choose to export it in 3MF or STL format (it goes into the downloads folder).
-All tools are in one long, monochrome ribbon of tiny icons at the top but there is a tool searcher.
-Like Fusion 360, sketching constraints are inferred as sketches are created and applying them works in a similar fashion. Their tiny symbols display in groups and associate to the point or line by a light grey line. Automatically applied constraints can make sketches behave in strange ways until you learn to find and remove the offending ones.
-Constraints and dimensions are movable so drawings can be uncluttered for printing.
-Section analysis is in the "Camera and Render Options" pop-up under the view cube.
-The spline and bezier sketching tools are not as interactive (a downside of running in a browser).
-Parameters, called variables, are more in your face; they are even shown in the timeline.
-Panning, rotating and the viewcube work a little differently. The iPad version of OnShape beats Fusion easily in this respect.
-OnShape does appear to support text along a path like Fusion.

The secret weapon of learning OnShape: An AI chatbot. Just ask any question about how to do something. One helpful migration from Fusion 360 is to print the sketch(es) (with constraints and dimensions) and work from that to create the equivalent in OnShape. An advantage of OnShape is that if you get stuck (e.g. drawing goes red), you can share a link with a more knowledgeable friend to tell you what is wrong. Most often the issue is conflicting constrains.

Context: 3D mechanical design software.., 3D Printed Pour-spout Forms.., My Breakup with Fusion.., OnShape parametric cloud-native CAD..

Saturday 6th September 2025

Classic Medalta Potteries Beer Bottle

Make this mold using OnShape and Fusion 360

Medalta classic beer bottle mold for slip casting

The original bottles were hand-thrown and very thick and heavy. These are perfect candidates for slip casting.

Drawing and 3D printing a case mold became my first success using OnShape. CAD is difficult, I really needed a tutorial that explained OnShape in terms of Fusion 360 I already knew. There wasn’t one! Now there is. This new procedure I have developed supersedes all of what I have done so far with beer bottle molds.

This is a test mold. This mold weighs 87g and the walls are printed to only 0.8mm thickness. We just pour in the plaster and remove this PLA print using a heat gun. Two natches are sufficient to keep the halves aligned perfectly. Pieces will shrink about 12%, thus this larger size. We will use a cone 6 casting body, tissue transfers for the decorations, the GA6-B glaze for the inside and shoulder and G2926B transparent for the body.

Context: Drawing the Same Mold.., Slip cast a stoneware.., Beer Bottle Master Mold..

Saturday 6th September 2025

Danny Downsized: He's Being Outsourced.

He should have seen this coming!

Danny downsized getting laid off

Management now thinks they can outsource his technical work. Danny was good, but he didn’t build a centralized, searchable record of material testing, shipment histories, specs, production problems, and solutions. Instead, his knowledge is buried in thousands of Excel and Word docs and PDFs. He should have used Insight-Live.com to organize, interlink, and preserve this critical data. Sadly, the company does not even realize what they face without Danny:

  • Slower problem-solving and loss of institutional memory.
  • Greater dependency on outsiders who lack long-term investment.
  • Inability to verify product claims.
  • Quality drift leading to recalls, rework, and higher warranty costs.
  • Innovation slowdown.
  • Eroding customer trust and ballooning consultant costs.

Had Danny been not just a watchdog but a technical innovator, suppliers and consultants would have been secured to support—not replace—his in-house expertise.

Context: Protect your reputation as.., 2 Skids of Material.., Tommy Turnback Ignored AI..

Sunday 31st August 2025

Tommy Turnback Ignored AI

By not adapting he wrote his own layoff notice

Tommy Turnback Is being laid off

Management says AI can do most of the technical work now. Tommy had no automation, no models, no data pipelines. Just “the way we’ve always done it,” trapped in spreadsheets and sticky notes. When the new AI system went live, his expertise didn’t plug in. It got left behind!

  • The AI could really have used his seasoned human oversight.
  • Years of hard-won knowledge lost in a digital junk drawer.
  • Outside consultants are charging a premium to relearn what he already knew.
  • Errors slip through because no one taught the machines better.
  • Innovation stalls while the company rebuilds what he could have bridged.

Technicians aren’t just there to keep things running—they should teach the future how to work. Refusing to adapt doesn’t protect your job. It writes your own pink slip.

Context: Danny Downsized He's Being..

Sunday 31st August 2025

Glazes Are Crazing on This Casting Porcelain

The casting process enables a unique and effective fix

Crazing clear glaze on a slip cast mug

This potter almost has the casting process working, making these beautiful porcelain mugs. They are fired at cone 6 using a transparent glaze over underglaze decoration. But the devil is in the details. Look closer to see it: Crazing. Why? The reason is evident on the SDS for the body. Notice it has 10.5-15.8% crystalline quartz (or silica). This is not enough to prevent crazing in typical glazes.

Almost always, the solution is to find or formulate a clear glaze having a lower thermal expansion (in this case, a lot lower). But with casting bodies, we have another option: Mix our own. Unlike glazes, porcelain recipes are typically just three materials: kaolin, feldspar and silica. The starting percentages are simple for cone 6: 30% feldspar to vitrify. And 25% silica to fit the glaze. That leaves 45% kaolin. It is that easy! Start with the L3778G recipe. Its information page is also a launching pad for dozens of links, enabling you to dig as deep as desired into understanding casting slips (the materials are cheap, so losing a few batches while you learn deflocculation is not a problem). Still think it is too difficult to mix our own? Consider that you need a propeller mixer anyway to prepare and adjust the slip and reprocess scrap. By mixing your own you'll be a more effective, and flexible slip caster.

Context: v3 Shelled AI Mug.., Another compelling reason for..

Friday 29th August 2025

Picasso’s Transparent Glaze

Micro-bubble free and crystal clear

Picasso low fire plate clear glaze

This plate, by Pablo Picasso, is on display in the art gallery on our Princess cruise ship. While others notice the underglaze designs, and the $40,000 price, I notice the absolutely crystal clear and bubble free transparent over glaze. How did he do that? At the Madoura studio they used leaded glaze, so Picasso himself doesn’t get the full credit. By his time, European low-fire traditions already had a well-matched clay/glaze system based. Glazes were made from mostly lead bisilicate frit with enough kaolin or ball clay to suspend the slurry. The lead melted so well that significant silica could be tolerated (20–30%) to reduce the COE. They didn’t use talc in the body, rather it would have contained 50-70% ball clay/kaolin, some feldspar as a filler (since it does not flux at low fire) and enough quartz to raise the thermal expansion within the range of the glaze.

Most potters struggling with borosilicate glazes would envy what leaded transparents can do. Any hope of even approaching them using boron glazes lies in keeping temperatures at or below cone 06, a thin glaze application, a low carbon body and ceramic stains rather than metal oxide colors.

Context: Lead bisilicate with his.., UK Slipware A Tradition.., Transparent Glazes

Thursday 21st August 2025

Glazing For the Photo Instead of the Pot.

Is it a “science project” or a functional glaze?

A runny reactive pottery glaze

This is a reactive pottery glaze, Jen’s Juicy Fruit. It runs. And crystallizes. That can look great on a test tile but for food surfaces there are strings attached. Behind the magic a tangle of headaches can be lurking: Leaching, crazing, poor durability. And even expense (this kind of melt fluidity usually requires wallet-busting lithium). But hey, why not go for it! Stuff it with metal oxides and get some real sparkle brewing. Then push it even harder, with slow cooling, for those big crystals. Congrats, now you’re brewing a science project. And flirting with leaching and toxicity. And there is more. These effects most often depend on high sodium or potassium (aka high feldspar), that’s a recipe for off-the-charts thermal expansion - and thus crazing. Is this glaze something you would want on a food surface? Suddenly that “wow” glaze starts to look… not so wow.

Hey, why not just fix it? Reduce that high KNaO, increase the SiO2 and Al2O3. Congrats. Now it looks totally different. And boring! With these types of glazes it is common that no matter what you do, you cannot maintain the character while fixing the problem. Why? The visual character depends on the problems! So use this. But not on functional ware.

Context: Reactive Glazes

Wednesday 20th August 2025

“Retail Rick” Has it Figured Out

He’s got a much better way to glaze

You may think this post is extreme or AI Slop. But I promote DIY, I do my best, this post took months to make. This is a response to the trends I have noted towards learned helplessness, skyrocketing costs and the dying breed of professional pottery. Even staff at stores, 75% of whose shelf space is taken by these expensive jars of "paint", express sadness at what they see happening. The remaining potters that I frequently visit express these same sentiments, feeling their hard-earned knowledge is considered useless by the new generation.

Rick doesn’t dig clay, crush rocks, or make glazes. Ew, messy. He buys commercial glazes in cute little jars, each the price of a steak dinner. Sure, back in the dark ages, potters used actual dirt and rocks. And, around here you can even get a ton of gravel or clay, for $20. But today, potters shell out twice that for one box and say, “Totally worth it!” OK, fine. But glaze is where it gets magical. A ton of local gravel is packed with feldspar, silica, calcium carbonate, dolomite — a whole cone-10 party (that can be moved to a cone 6 neighborhood with a little frit). Grind it, add clay, dip, done. How is it possible that an overloaded pickup truck full costs half the price of a single 500ml jar Rick uses? Something’s upside down here! Rick says: “Why mess with base recipes or spend all that effort learning and testing DIY dipping glazes when I can spend minutes multi-layering these commercial paints”! Of course, he has to brush up the price to pay for them! And sure, some customers might question how glazes that have such intense metallic colors and run like mascara in the rain are not silica-starved metal-oxide sludge. Rick answers: “They have safety labels, with fancy symbols, so I don’t have to think about that”. The icing on the cake it how well they photograph and how good they look on Rick’s social. He really has this thing figured out. Tradition is overrated anyway, right?

Context: Are drippy glazes what.., Commercial hobby brushing glazes..

Sunday 17th August 2025

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  • I have been in the pottery business for 52 years, Pemco use to be 10 miles from us. Your advise on solving our glaze problem worked perfectly and you explained it so well. I have had this problem for 7 years, re-firing lots of ware. Pemco guys and Pfaltzgraff Pottery glaze dept. told me different recipes but it never solved the problem. None of them talked about firing cycles. Tony, how did you get so smart? God has Blessed you.
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  • I just wanted to say, thank you! I’m relatively new to pottery, taking a mostly self-taught approach and I’m at the stage where glazing is in my mind. I don’t want to be (and can’t see myself ever) buying glazes from commercial suppliers. I want to learn my craft with glaze as much as I do with my clay preparation and pottery making. I’ve seen “the dragon” and been uninspired by so much of what I find online and to be honest, in many glaze books. It seems more popular to try and present a mass of glaze possibilities than to offer a learning experience beyond being told a glaze needs a melter, a refractory and a glass-maker. Enough to offer a very basic understanding, but nothing upon which to build the understanding that will allow some degree of mastery (or at least influence) of your glaze making. I am so pleased to have found digitalfire.com. You’ve shown me exactly how to approach and understand glazing, giving me the foundation for approach I sought. I was thinking of base glazes and what you’ve shown me about working on from those is fantastic and exactly what I was looking for. To have a reliable base glaze to modify and develop to meet different needs; to understand how to shift a melting point or adjust the surface gloss; to come to know how the mechanisms in a glaze and understanding them gives me the route to creating glazes that realize my intentions - wow! I can’t thank you enough. Rather than having to form a dumb reliance on a book of recipe cards and a bunch of website bookmarks (which I wasn’t wanting to go for) you’ve given me the foundation for a lifelong development and understanding of the glazes I will make, that will become “my” glazes. You have really opened my mind to the whole subject and it doesn’t seem to be a problem that I’m no scientist or chemist. You’ve shared your knowledge in a way that is completely approachable and remarkably easy to understand for someone without any kind of science/chemistry background.
  • In the 4 decades or so of my academic career (I taught ceramics as a major of the Fine Art degree at the University of Kwa-Zulu-Natal, South Africa), glaze chemistry was one of my favourite subjects, though it was too 'scientific' for most students! Your Insight-Live programme is really super! Thanks once again for all you are doing to keep the discipline alive and kicking.
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  • First, I love your site so much! Thank you for the countless hours that have been put into this!
  • Your site is amazing and your videos too. Such an inspiration.



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