Monthly Tech-Tip from Tony Hansen SignUp	No tracking! No ads! That's why this page loads quickly!

All Articles

Glaze Recipes: Formulate and Make Your Own Instead

Description

The only way you will ever get the glaze you really need is to formulate your own. The longer you stay on the glaze recipe treadmill the more time you waste.

Article

The traffic in glaze recipes has had a net negative effect on functional ceramics in education, hobby, and industry. Books and the internet are filled with recipes that are illogical and emphasize appearance at the expense of safety, practicality, or cost. 'Affairs' with these 'naked' (undocumented) recipes have left many numbed regarding their accountability and even ill-equipped to recognize true quality. This trade in recipes fosters a culture that runs counter to the idea of 'understanding' and controlling our materials and recipes, it breeds ignorance of oxide and material sciences and the true nature of the ceramic process. It deludes many into an 'easy-fix' mentality that seeks 'foolproof' solutions that end up being blind allies that waste years and teach nothing. Implied 'ethics' suggest that the traffic in recipes be accompanied by documentation to prove givers conscientious and by critical analysis and testing on the part of recipients willing to 'understand' and adjust. Weak, leachable, difficult-to-clean, crazed, shivered, leaching glazes hurt the reputation of the pottery and ceramic industry. It is time that a 'want-to-know-why' mindset toward formulating and adjusting glazes on the oxide and material level is fostered in students. It is time that a stigma is attached to joining the 'illicit trade' in recipes and using trial-and-error bull-in-a-china-shop approaches to glaze formulation.

We recommend a 'base glaze with variations' starting model. As your understanding of a base glaze improves over a period of years you can develop the ability to identify its mechanism and learn to transplant them into different bases. In this way, you can minimize the number of base recipes you use. In addition, as you improve each base (e.g. its application properties, fired harness, fit adjustability, etc.) all the variations based on it will inherit the improvements.

In education and pottery circles the trade in recipes has encouraged a 'roulette wheel' approach to choosing glazes and in big industry there is a brain-drain toward suppliers and consultants while many manufacturers are becoming more and more helpless. At Digitalfire we personify these dangerous trends and attitudes as 'The Dragon'. The dragon wants you to believe that casual potters are exempt from technical concerns. He fosters blissful attitudes that keep us on an endless treadmill of glaze recipe experimentation and disappointment or on suppliers that lack a connection to unique circumstances and customer-specific problems. The dragon wants us to think that glaze chemistry is too complicated and too much trouble.

The Formula Viewpoint, Key to Taking Control

Chemistry, that is, viewing your glazes as formulas of oxides rather than recipes of materials, is an invaluable tool to deal with things like hardness, strength, porosity, leaching, thermal shock resistance, chip resistance, glaze fit, color compatibility, of your functional ware. A typical formula contains eight or so oxides and it takes a lot less study to figure out what these contribute than it does to figure out what 100 different materials do. Glaze software, like Insight-live, provides the simplest way to work with glaze formulas.

Related Information

We fight the dragon that others do not even see

Tap picture for full size

There are thousands of ceramic glaze recipes floating around the internet. People dream of finding that perfect one, but they often only think about the visual appearance, not of the usability, function, safety, cost or materials. That resistance to understanding your materials and glazes and learning to take control is what we personify as the dragon. Using the resources on this site you could be fixing, adjusting, testing, formulating your own glaze recipes. Start with your own account at insight-live.com.

Glaze recipes trafficked online waiting for a victim to try them!

Tap picture for full size

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).

What has the trust in online recipes come to?

Tap picture for full size

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. Admittedly, this glaze is meant for layering over others - but the source did not say that. This underscores misguided trust in trafficked recipes that most often lack sufficient 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 and glaze thickness are involved. People who post glaze recipes like this often do not document them well because they do not fully understand their mechanisms.

Trying to avoid knowing anyting about glaze chemistry? Be ready for drama!

Tap picture for full size

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, addicted to the traffic of recipes that never seem to work.

Knowing about recipe limits could save you the work of testing this glaze

Tap picture for full size

This is an example of a recipe being trafficked online that raises red flags just looking at it. The first red flag: There is no silica! That means this is a low fire glaze masquerading as middle temperature, so it is going to run during firing (run a lot). It will also mean poor durability. There is a ton of feldspar, that means a high level of sodium. Without low-expansion MgO to counterbalance it's high thermal expansion the glaze is likely going to craze badly. The mechanism of the crystallization is titanium over-supply, this has triple the maximum I would ever put in a glaze. The crystallization happens during cooling in the kiln (producing the visual effect being sought). But the the surface produced will cutlery mark and stain, probably very badly. Given the unbalanced chemistry this has, any colorant added will likely be leachable! I tested it and all my fears were realized. My slow-cool firing made the surface so dry it was very unpleasant to touch. Maybe this needs fast cooling. But who knows, there are no notes. This does not appear to belong on any functional ware, inside or outside. Someone noted that people use this to produce layering effects (see links). That begs documentation on how that wold work. Without gum would it lift and crawl as layers are added over it. Would you have to overlay every square inch? Would it still craze? All the how-to information needed to make it work are more important that the recipe itself.

Better to mix your own cover glazes for production?

Tap picture for full size

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.

Low fire heaven: Use commercial underglazes but make your own clear over glaze

Tap picture for full size

Decorate ware with the underglazes at the leather hard stage, dry and bisque fire it and then dip-glaze in a transparent that you make yourself (and thus control). These mugs are fired at cone 03. All have the same transparent glaze (G2931K), all were decorated with the same underglazes. Notice how bright the colors are compared to middle or high temperature. On the left is a porous talc/stoneware blend (Plainsman L212), rear is a fritted Zero3 stoneware and right is Zero3 fritted porcelain. When mixed properly you can dip ware in this glaze and it covers evenly, does not drip and dries enough to handle in seconds! Follow the Zero3 firing schedule and you will have ware of amazing quality.

Commercial glazes on decorative surfaces, your own on food surfaces

Tap picture for full size

These cone 6 porcelain mugs are hybrid. Three coats of a commercial glaze painted on outside (Amaco PC-30) and my own liner glaze, G2926B, poured in and out on the inside. When commercial glazes (made by one company) fit a stoneware or porcelain (made by another company), it is often purely an accident! So test thoroughly or just use them on the outsides. For inside food surfaces make or mix a liner glaze already proven to fit your clay body, you have to option to make it as a dipping glaze or brushing glaze. One that is sensible enough to fit common sense recipe limits and not have an unbalanced chemistry. And you can use quality materials that you know deliver no toxic compounds to the glass and that are proptioned to deliver a balanced chemistry.

Think the idea of mixing your own glazes is dead? Nope!

Tap picture for full size

These are two pallets (of three) that went on a semi-trailer load to a Plainsman Clays store in Edmonton this week. They are packed with hundreds of bags of powders used to mix glazes. More and more orders for raw ceramic materials are coming in all the time. Maybe you are using lots of bottled glazes but for a cover or a liner glaze it is better to mix your own. And cheaper! And there are lots of recipes and premixed powders here to do it. One of the big advantages is that when you dip ware into a properly mixed slurry it goes on perfectly even, does not run and dries on the bisque in seconds. No bottled glaze can do that.

Another good reason to mix your own glazes (or casting bodies)

Tap picture for full size

These are cone 6 commercial glazes made by a popular US manufacturer. The body is a cone 6 casting porcelain made by another popular manufacturer. Zoom the photo, they are all crazing! Which company is at fault? Neither has the responsibility (or is able, especially with stonewares and porcelains) to match their product to that of every other company. The pattern we see here points-the-finger at the body. Mid-fire porcelains craze glazes much more if they lack sufficient silica (20% is minimum). It is difficult for manufacturers to achieve this since much more feldspar is needed to vitrify the body. And the potter does not know the recipe of the porcelain. What to do then? One option is to get a porcelain from another supplier, with assurances from them about glaze fit. Better yet, mix your own. Casters need a mixer anyway, so why not? We can help you with a recipe if you need it. Actually, mixing your own glaze also would get rid of those micro-bubbles and give a glassier surface.

Brush-on commercial pottery glazes are perfect? Not quite!

Tap picture for full size

Paint-on glazes are great sometimes. But they are even greater if you know the recipe, then you can make more and make a dipping version for all the times when that is the better way to apply. Why is that better? Because you have a huge advantage over a glaze manufacturer: You already have clear glossy and matte base recipes that fit and work on your clay body. You can add the stains and opacifiers to these (with gums to make them paintable) and make your own jars. Don't have base recipes??? Let's get started developing them with an account at insight-live.com (and the know-how you will find there)!

These pieces reveal four benefits of making your own low fire glazes

Tap picture for full size

These were fired at cone 04. All three transparent glazes are on the same body (made from talc and ball clay). And fired at the same temperature - cone 04. Left to right: Amaco LG10, G3879C and Crysanthos SG213. We mix the middle one ourselves, from a recipe that employs a high percentage of Fusion Frit F-524. The first of four obvious benefits is evident: While frit F-524 is expensive, the glass it produces is more transparent and less iron-contaminated - so it transmits the whiter body color better. Second, the two commercial glazes are crazing. We fixed that using another expensive material, the super low expansion Ferro Frit 3249 (or its equivalent Fusion Frit F-69). Although containing significant MgO, that frit is an amazing melter even at this low temperature. Third, notice that the outer two mugs have micro-pinholes and surface defects that the middle one does not have. The reason for that is not obvious but it could be they have lower melt fluidity. The fourth benefit - the recipe can be adjusted to improve it. Yes, mixing your own glazes can really pay off in ware quality. At stoneware temperatures the opposite can also be achieved by mixing your own - creating glazes that use less expensive and more readily available materials.

Global supply chain issues? Learn to mix and adjust your own bodies, glazes

Tap picture for full size

Material prices are sky rocketing. And, the more complex your supplier's supply chain the more likely they won't be able to deliver. How can you adapt to coming disruption, even turn it into a benefit? Learn to create base recipes for your glazes and even clay bodies. Learn now how to substitute frits and other materials in glazes (get the chemistry of frits you use now so you are ready). Even better: Learn to see your glaze as an oxide formula. Then calculate formula-to-batch to use whatever materials you can get. Learn how to adjust glazes for thermal expansion, temperature, surface, color, etc. And your clay bodies? Develop an organized physical testing regimen now to accumulate data on their properties, learn to understand how each material in the recipe contributes to those properties. Armed with that data you will be able to adjust recipes to adapt to changing supplies.

Links

Articles	G1214Z Cone 6 matte glaze This glaze was developed using the 1214W glossy as a starting point. This article overviews the types of matte glazes and rationalizes the method used to make this one.
Articles	Ball Milling Glazes, Bodies, Engobes Industries ball mill their glazes, engobes and even bodies as standard practice. Yet few potters even have a ball mill or know what one is.
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 ceramic glazes.
Recipes	G2926B - Cone 6 Whiteware/Porcelain transparent glaze A base transparent glaze recipe created by Tony Hansen for Plainsman Clays, it fires high gloss and ultra clear with low melt mobility.
Glossary	Cone 6 Also called "middle temperature" by potters, cone 6 (~2200F/1200C) refers to the temperature at which most hobby and pottery stonewares and porcelains are fired.
Projects	Recipes

By Tony Hansen Follow me on

Got a Question?

Buy me a coffee and we can talk

---

https://digitalfire.com, All Rights Reserved
Privacy Policy