A Low Cost Tester of Glaze Melt Fluidity
A One-speed Lab or Studio Slurry Mixer
A Textbook Cone 6 Matte Glaze With Problems
Adjusting Glaze Expansion by Calculation to Solve Shivering
Alberta Slip, 20 Years of Substitution for Albany Slip
An Overview of Ceramic Stains
Are You in Control of Your Production Process?
Are Your Glazes Food Safe or are They Leachable?
Attack on Glass: Corrosion Attack Mechanisms
Ball Milling Glazes, Bodies, Engobes
Binders for Ceramic Bodies
Bringing Out the Big Guns in Craze Control: MgO (G1215U)
Ceramic Glazes Today
Ceramic Material Nomenclature
Ceramic Tile Clay Body Formulation
Changing Our View of Glazes
Chemistry vs. Matrix Blending to Create Glazes from Native Materials
Concentrate on One Good Glaze
Cone 6 Floating Blue Glaze Recipe
Copper Red Glazes
Crazing and Bacteria: Is There a Hazard?
Crazing in Stoneware Glazes: Treating the Causes, Not the Symptoms
Creating a Non-Glaze Ceramic Slip or Engobe
Creating Your Own Budget Glaze
Crystal Glazes: Understanding the Process and Materials
Deflocculants: A Detailed Overview
Demonstrating Glaze Fit Issues to Students
Diagnosing a Casting Problem at a Sanitaryware Plant
Drying Ceramics Without Cracks
Duplicating Albany Slip
Duplicating AP Green Fireclay
Electric Hobby Kilns: What You Need to Know
Fighting the Glaze Dragon
Firing Clay Test Bars
Firing: What Happens to Ceramic Ware in a Firing Kiln
First You See It Then You Don't: Raku Glaze Stability
Fixing a glaze that does not stay in suspension
Formulating a Clear Glaze Compatible with Chrome-Tin Stains
Formulating a Porcelain
Formulating Ash and Native-Material Glazes
Formulating Your Own Clay Body
G1214M Cone 5-7 20x5 Glossy Base Glaze
G1214W Cone 6 Transparent Base Glaze
G1214Z Cone 6 Matte Base Glaze
G1916M Cone 06-04 Base Glaze
G1947U/G2571A Cone 10/10R Base Matte/Glossy Glazes
Getting the Glaze Color You Want: Working With Stains
Glaze and Body Pigments and Stains in the Ceramic Tile Industry
Glaze Chemistry Basics - Formula, Analysis, Mole%, Unity, LOI
Glaze chemistry using a frit of approximate analysis
Glaze Recipes: Formulate Your Own Instead
Glaze Types, Formulation and Application in the Tile Industry
Having Your Glaze Tested for Toxic Metal Release
High Gloss Glazes
How a Material Chemical Analysis is Done
How desktop INSIGHT Deals With Unity, LOI and Formula Weight
How to Find and Test Your Own Native Clays
How to Liner-Glaze a Mug
I've Always Done It This Way!
Inkjet Decoration of Ceramic Tiles
Interpreting Orton Cones
Is Your Fired Ware Safe?
Leaching Cone 6 Glaze Case Study
Limit Formulas and Target Formulas
Low Budget Testing of the Raw and Fired Properties of a Glaze
Low Fire White Talc Casting Body Recipe
Make Your Own Ball Mill Stand
Making Glaze Testing Cones
Monoporosa or Single Fired Wall Tiles
Organic Matter in Clays: Detailed Overview
Outdoor Weather Resistant Ceramics
Overview of Paper Clay
Painting Glazes Rather Than Dipping or Spraying
Particle Size Distribution of Ceramic Powders
Porcelain Tile, Vitrified or Granito Tile
Rationalizing Conflicting Opinions About Plasticity
Ravenscrag Slip is Born
Recylcing Scrap Clay
Reducing the Firing Temperature of a Glaze From Cone 10 to 6
Single Fire Glazing
Soluble Salts in Minerals: Detailed Overview
Some Keys to Dealing With Firing Cracks
Stoneware Casting Body Recipes
Substituting Cornwall Stone
Super-Refined Terra Sigillata
The Chemistry, Physics and Manufacturing of Glaze Frits
The Effect of Glaze Fit on Fired Ware Strength
The Four Levels on Which to View Ceramic Glazes
The Majolica Earthenware Process
The Physics of Clay Bodies
The Potter's Prayer
The Right Chemistry for a Cone 6 MgO Matte
The Trials of Being the Only Technical Person in the Club
The Whining Stops Here: A Realistic Look at Clay Bodies
Those Unlabelled Bags and Buckets
Tiles and Mosaics for Potters
Toxicity of Firebricks Used in Ovens

Understanding Ceramic Materials
Understanding Ceramic Oxides
Understanding Glaze Slurry Properties
Understanding the Deflocculation Process in Slip Casting
Understanding the Terra Cotta Slip Casting Recipes In North America
Understanding Thermal Expansion in Ceramic Glazes
Unwanted Crystallization in a Cone 6 Glaze
Variegating Glazes
Volcanic Ash
What Determines a Glaze's Firing Temperature?
What is a Mole, Checking Out the Mole
What is the Glaze Dragon?
Where Do I Start?
Why Textbook Glazes Are So Difficult

Trafficking in Glaze Recipes


The trade is glaze recipes has spawned generations of potters going up blind alleys trying recipes that don't work and living with ones that are much more trouble than they are worth. It is time to leave this behind and take control.


Ceramic suppliers can’t sell their stocks of books anymore. We supposedly don’t need them because we are all binging on Google, YouTube, Facebook and Instagram ceramics. And recipes on Glazy. It’s exploding. A lot is good, but one issue that can waste so much time is the “trafficking of glaze recipes” that don’t work. Many studios are "bucket morgues" of failed tests (and the powdered materials bought to try them). People spend money to mix ridiculous, expensive recipes, ones that end up in the garbage. Are you still addicted, going again and again for more punishment? Or did you find one that works — sometimes? But punishes you all the others? Are you really learning anything?

More than ever, as a person that wants to understand glazes, how to formulate, adjust and fix them myself; I am marginalized. Lonely. As a ceramic culture we are getting more and more mentally lazy and wasting more and more money to make less and less technically acceptable ware. This article is a little disjointed and wandering, that reflects my lack of ability to step back far enough to understand fully what is happening to our craft and science.

Notwithstanding, there are gems out there to be found and adapted. But how can you find them while recognizing the time wasters? Ask yourself: 1: What do I need? 2: What do I want?

Let’s answer #1 first. In production or hobby ceramics you need a base transparent that fits your clay body, reliably fires crystal clear without micro-bubbles, does not craze or scratch or mark or leach, has good application properties, whitens with zircon and colors with stains. Likewise for a matte base. These base recipes, along with knowledge how to mix (control SG and thixotropy) and fire them are worth any effort to get. Not just because they can cover the functional surfaces and are well behaved but, as noted, the excitement of discovery can be satisfied by adding colourants, opacifiers and variegators. Or they can be coloured as a first coat on which to layer all sorts of commercial decorating products. Technically this may be all you need so you can stop reading here.

Admittedly you might have more specialized desires (e.g. a fluid melter, a low Al2O3 base for growing crystals). Or the color you want might require special chemistry in the base (e.g. significant BaO, presence or absence of ZnO or MgO, high levels of CaO). These are standalone recipes, exceptions to the base-with-additions approach. Are you really sure this is what you need? That the approach I described in the previous paragraph is not what you need? Could a simple stain addition to a base be all you need? Could you transplant the “mechanism” in the recipe that has caught your attention into your own clear glaze?

Ok, I get it. You really do need something special. First, don’t be naive, such recipes often come with baggage (like issues with crazing, leaching, hardness, running, consistency, application) so go in with both eyes open. So what is the best way to find one? Many people want a shortcut: throw the “google dice” and land directly on a reactive glaze that crystallizes, variegates, swirls and runs in rivulets, dances with wild colors or subtle effects that highlight every contour. Having no side effects! They want the buzz that kiln openings of such “street recipes” give. Unfortunately the real world is just not like this. The people who share them fail to describe all the details to follow to make them look like the picture. Or they do not understand what they are sharing. It’s those pictures that get us addicted and coming back for more punishment!

Consider some of the reasons why a glaze recipe might not "travel" very well.

Misguided Trust

If you are a beginner in ceramics you might reason: "Why would anyone post a recipe online if they know it does not work?". However (noting the above-mentioned) they likely do not know it does not work. Or they are unaware that their narrow circumstances are, by coincidence, an enabler for a small window in which it does do something they like. Or they have a different idea of what "working" really means, maybe emphasizing aesthetics, possibly to the extent of totally ignoring functionality and practicality. Misguided trust in online recipes can discourage newbies who cannot find success with them, blaming themselves. It can even go further: Some people, who confront failure in trying a recipe for the first time, actually blame specific materials in the recipe, flaming manufacturers online "who cannot keep their products consistent". This kind of thinking is misguided, even if it were true that a recipe depends on a material being absolutely consistent, that kind of fragile recipe would not be worth using.

What is Much Better Than Recipes

Yes, there is something that travels even better than oxide formulas. It is the knowledge of what each oxide type contributes to a glaze, what each mineral type does to give it fired personality, and how they affect physical working properties. Each new recipe either confirms or fine tunes your existing oxide-effect knowledge, or educates you in the effects of its special purpose source materials (i.e. colorants, opacifiers, crystal forming agents) or unique formula (i.e. crystals from high CaO and low Al2O3 ). Each can be adapted to your own proven base recipes.

Add a smattering of line blending and trial and error adjustment, and you can make anything you want; adjust it any way you want. You can tell the glaze what to do. So why jump through hoops trying to pacify temperamental recipes that are always throwing tantrums in your kiln? You don't have to put up with that any more.

Related Information

Tried and True recipes. Really?

The cover of a book: 15 Tried and True Cone 6 Glaze Recipes

Books and web pages with flashy pictures are the centrepiece of an addiction-ecosystem to recipes that often just don't work. Maybe these are "tried" by a lot of people. But are they "true"? Most are so-called "reactive glazes", outside normal practice - to produce visual interest they run, variegate, crystallize, pool, break, tint, go metallic, etc. But this happens at a cost. And inside special procedures and firing schedules that need explaining. It is not obvious these are understood by the recipe authors or sharers. And these recipes are dated and contain troublesome and unavailable materials. We use frits now to source boron. Stains are superior to raw colorants, even in glazes like this. Many of these will craze badly. And many will not suspend in the bucket. And will run during firing. Reactive glazes have other common issues: Blistering, leaching, cutlery marking, fuming. Trying colors in differing amounts in different base recipes is a good idea. But the project is most beneficial when it shows color response in terms of quality recipes of contrasting chemistries. The point of all of this: Understand a few glazes and develop them, rather than throwing spaghetti against the wall hoping something sticks. Commercial reactive glazes are an alternative also.

Want bright orange? Use a stain in your own base transparent recipe.

Fired glaze tiles showing an orange promise, what actually came out and a better way

Orange is a very difficult color in ceramics. Inclusion stains are the only reliable method, they universally used in industry. But you could ignore that and try a bunch of recipes online. When they are presented on flashy web pages they can look tantalizing. But beware! Are the exotic materials you need to buy worth it. Will it actually fire orange? Will it craze or run or blister or leach or cutlery mark or crawl or settle like a rock in the bucket? It is much better to put an orange encapsulated stain into a transparent glaze you already know works on your clay. Then just experiment with percentage to get the color you want. Or, how about trying a premixed orange at low fire? Ware can be amazingly functional at low temperatures (e.g. cone 03-02) and bright colours labelled for cone 06 mostly work fine in that range.

Is that recipe you found online really what you think it is?

It contains significant Frit P-25, I googled that to Digitalfire, it contains 1.8% fluorine! When that gases off during firing are you really equipped to deal with fluorine gas in your studio? One answer is to substitute my own frits (which of course do not contain fluorine). I did the calculations in my account at insight-live.com (see the recipes side-by-side). In the formula, I substituted the F (fluorine) for a mix of CaO/MgO. In the recipe, I substituted Ferro Frit 3110 (it is also a high-sodium frit) for the P-25, then I juggled the rest of the recipe to match up the oxides. More Gerstley Borate supplies the lost B2O3, more ball clay supplies the lost Al2O3 and less silica is needed (because the ball clay brought along more). I ended up with a recipe that is going to suspend much better (more clay) and was able to eliminate the whiting (because the rest of the new recipe is supplying more CaO). This recipe has a high thermal expansion, that means crazing. Would it not be easier to simply add a red stain to a clear glaze you already have that is working well on your clay bodies?

What has the trust in online recipes come to?

These tests of a recipe called "Strontium Crystal Magic". The potter tried it on different bodies and firings. But instead of producing the magic crystals like the pictures, the surfaces fired totally matte. Reasoning "why would anyone put a recipe on line that does not work", she blamed one of the materials. Others fed that with rumours of claimed issues in its consistency. This is misguided trust in trafficked recipes (ones with insufficient documentation). Crystal glazes, by necessity, need to have a high melt fluidity. The crystals develop best with a specific cooling curve having a controlled fall at a narrow temperature range. Cool faster, they don't grow, slower and they matte the entire surface. Other factors, like clay body, glaze thickness are also involved. People who post glaze recipes like this often do not fully understand their mechanisms.

The fact that it applied like this was not worth mentioning?

Recipes trafficked online seldom include important information. How could the author of this one not mention this problem? The slurry turns to a gel and fills with bubbles. And then you have to add water again. The extra water makes it shrink more, compromising the bond with the bisque so it peels away when overgrazed. Later more water is needed because it gels again. After that it cracks on drying and the glaze crawls on firing. Is this really worth it? Actually, this recipe is fixable, the material at fault can be substituted (using a little glaze chemistry) to produce a much easier-to-use slurry.

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).

My head was in the clouds and I appreciate the grounding!

She was searching for a a mat mottled white, rustic. For functional surfaces. And it contained this frit. This is what she said after we talked about whether she should really make that recipe, or search for a matte matte that is more balanced. The source from which she got it did not mention the barium content.

You have to know about chemistry to progress in ceramics! Maybe quilting would be better!

A periodic table of oxide with elements important to ceramics highlighted

Maybe you don't think it is necessary to know anything about glaze chemistry to be a potter. Or a technician at a production facility. This thinking depends on how much mystery you mind tolerating. Because the reason for many of the problems you will encounter with glazes relates fundamentally to their chemistry. Perhaps you have other "social" actors in your sphere who also specialize in the "know as little technical stuff as possible" mindset. Who treat glazes like acrylic paint that comes in tubes - it is just color! From these people you will get buying advice on expensive jars of tacky-looking "goop" that you have to laboriously paint on in layers. Or it will mean you'll be more likely to get trapped on the recipe treadmill (addiction to the traffic of recipes that never seem to work). Maybe it is for the best, if ceramics is that hard then maybe you could take up quilting instead! They don't need to worry about chemistry!

Better to mix your own cover glazes for production?

Yes. In this case the entire outside and inside of the mug need an evenly applied coat of glaze. In production, it would not make sense to attempt this by painting. For these reasons: Cost, quality, convenience. The right pail has 2 gallons of G2934Y base with 10% Cerdec yellow stain: $135. Cost of jars with the same amount: Almost $300! And you have to paint them on in three coats with drying in between. The one in the pail is a true dipping glaze (unlike dipping glazes sold by glaze manufacturers that dry slowly and drip-drip-drip just like brushing ones). This one dries immediately after dipping in a perfectly even layer (if mixed according to our instructions). And a bonus: This pail can be converted to brushing or base-layering versions using CMC gum.

This cone 6 transparent looked good, but I still improved it alot

The green boxes show cone 6 Perkins Studio Clear (left) beside an adjustment to it that I am working on (right). I am logged in to my account at insight-live.com. In the recipe on the right, code-numbered G2926A, I am using the calculation tools it provides to substitute Frit 3134 for Gerstley Borate (while maintaining the oxide chemistry). A melt-flow GLFL test comparison of the two (bottom left) shows that the GB version has an amber coloration (from its iron) and that it flows a little more (it has already dripped off). The flow test on the upper left shows G2926A flowing beside PGF1 transparent (a tableware glaze used in industry). Its extra flow indicates that it is too fluid, it can accept some silica. This is very good news because the more silica any glaze can accept the harder, more stable and lower expansion it will be. You might be surprised how much it took, yet still melts to a crystal clear. See the article to find out.

Improving a clear by substituting frit for Gerstley Borate

Melt fluidity test showing Perkins Studio clear recipe original (left) and a reformulated version that sources the boron from Ferro Frit 3134 instead of Gerstley Borate (right). The later is less amber in color (indicating less iron) and it melts to very close to the same degree.

The traffic in glaze recipes will burn your success!

They might look great on a fancy website, but what are the chances they will actually work in your circumstances? Very low. After trying many glazes you may think you have found one that works. But does it really? Or is it erratic and unreliable? Difficult to use. Does it leach or craze or shiver or pinhole or blister? Or give you other problems? Be critical and cautious about recipes you find.

A good matte glaze. A bad matte glaze.

A melt fluidity comparison between two cone 6 matte glazes. G2934 is an MgO saturated boron fluxed glaze that melts to the right degree, forms a good glass, has a low thermal expansion, resists leaching and does not cutlery mark. G2000 is a much-trafficked cone 6 recipe, it is fluxed by zinc to produce a surface mesh of micro-crystals that not only mattes but also opacifies the glaze. But it forms a poor glass, runs too much, cutlery marks badly, stains easily, crazes and is likely not food safe! The G2934 recipe is google-searchable and a good demonstration of how the high-MgO matte mechanism (from talc) creates a silky surface at cone 6 oxidation the same as it does at cone 10 reduction (from dolomite). However it does need a tin or zircon addition to be white.

Popular white engobe recipe that does not work at cone 6

This is Odyssey slip, a engobe recipe that is trafficked on the web. It is recommended for low, medium and high fire ware. It is 30% Ferro Frit 3110 and 70% ball clay. This is a bi-clay strip, a sandwich of two plastic clays rolled into a thin slab and cut into a bar (to make the bar the Odyssey slip was dewatered to typical pottery clay stiffness). We are looking at the engobe side of an EBCT test (the other side is Plainsman M390). During the latter stages of the firing the engobe has begun to melt and blister and darken in color (which it should not be doing). During earlier stages of firing this engobe would certainly have had a higher shrinkage and would have bent the bar its way. But it is now bent the other way. That means the engobe could well be under compression (having a lower thermal expansion than the body). Or the body could simply have pulled it the other way when the engobe lost its rigidity. Either way, the engobe does not fit this body at this temperature.

Trafficked online recipes waiting for a victim to try them!

A pile of printed recipes to try, but few are likely to work

You found some recipes. Their photos looked great, you bought $500 of materials to try them, but none worked! Why? Consider these recipes. Many have 50+% feldspar/Cornwall/nepheline (with little dolomite or talc to counteract their high thermal expansion, they will craze). Many are high in Gerstley Borate (it will turn the slurry into a bucket of jelly, cause crawling). Others waste high percentages of expensive tin, lithium and cobalt in crappy base recipes. Metal carbonates in some encourage blistering. Some melt too much and run onto the kiln shelf. Some contain almost no clay (they will settle like a rock in the bucket). A better way? Find, or develop, fritted, stable base transparent glossy and matte base recipes that fit your body, have good slurry properties, resist leaching and cutlery marking. Identify the mechanisms (colorants, opacifiers and variegators) in a recipe you want to try and transplant these into your own base (or mix of bases). And use stains for color (instead of metal oxides).

The first of 15 "Fool-Proof Recipes" wrecked my kiln shelf!

A melt flow tester showing how a normal glazes runs when melting compared to this one

This is recommended in the booklet "15 Tried and True Cone 6 Glaze Recipes". This melt flow tester compares it with a typical cone 6 glossy, G2926B. This recipe is 90% Frit 3110 and 10% kaolin and their booklet recommends adding stains to it. But anyone knowing a little about this frit knows it would run off this flow tester even before bisque temperatures. It is crazy to recommend this. Even as a crackle. For cone 6 it needs to be diluted much more, not just with kaolin but also silica. I knew this would run but I underestimated its melt fluidity. I put a large tile below the tester to catch overrun, yet the melt ran off that and a big three-cm-wide blob melted through the kiln wash and so far into my zircon shelf I cannot chip it off! I cannot imagine how many people have tried this on vertical surfaces and had the same thing happen. The lesson: Use common sense when looking at recipes. Even if their authors did not!


Glossary Base Glaze
Understanding your transparent glaze and learning how to adjust its melt fluidity, thermal expansion, color response, etc is a base on which to build all your other glazes.
Glossary Limit Recipe
This term refers to critical thinking ability that potters and technicians can develop to recognize recipes having obvious issues and merit, simply by seeing the materials and percentages.
Glossary Glaze Recipes
Stop! Think! Do not get addicted to the trafficking in online glaze recipes. Learn how they work. Understand them. Then make your own or adjust/adapt what you find online.
Projects Recipes
Media Analysing a Crazing, Cutlery-marking Glaze Using Insight-Live
Media Insight-live, a Cure For Long-time Gerstley Borate Sufferers!
Articles What is the Glaze Dragon?
At Digitalfire we use a Dragon to personify the kinds of thinking that prevent potters, educators and technicians from understanding and therefore controlling their glazes.
Articles A Textbook Cone 6 Matte Glaze With Problems
Glazes must be completely melted to be functional, hard and strong. Many are not. This compares two glazes to make the difference clear.

By Tony Hansen

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