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

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
Trafficking in Glaze Recipes
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

G1916M Cone 06-04 Base Glaze

Description

This is a frit based boron base glaze that is easily adjustable in thermal expansion, a good base for color and a starting point to go on to more specialized glazes.

Article

Jan 2017: We recommend that you also read the documentation for G1916Q (link below). It employs different frits to accomplish the same objective and has a wider range of adjustment while remaining transparent.

The purpose of this page is not just to publish another recipe and throw you to the glaze dragon. For many the 'glaze recipe culture' and addiction to undocumented 'naked formulas' has meant countless 'blind alleys', years of wasted efforts, and gradual abdication of control to recipes that overstay their welcome and teach nothing. It has fostered a generation of ceramists with numbed consciences regarding their accountability for glazed ware they give or sell to others. The purpose here is to give you a 'starting point' so that you can exercise a degree of control over a base glaze to vary its color, surface, expansion, variegation, melting temperature, etc. (this site deals extensively with raising your expectations and understanding with regard to your glazes). The starting glaze recipe about which this page speaks is linked below. But instead of just going straight there, please read this background first.

One of the appeals of low fire and Majolica ware is that there is only one glaze to worry about. Generally artists employ a good transparent that they can add 15-20% zircon opacifier to to make a white. However, more than any other pottery process, technicians must be sure that their clay and glaze are compatible (have similar thermal expansions to minimize crazing and shivering). Even if the glaze does not visibly craze or shiver the already comparatively low strength of ware can be severely compromised.

Crazing and shivering are far more likely at lower temperatures because the less developed interface between clay and glaze is less able to absorb a bad fit. This is actually a blessing in disguise because it forces you to compensate. Crazing is more likely on a body made of clay materials only, shivering is possible on bodies containing talc.

The key to a good-fitting Majolica glaze is one word: Adjustability. Forget about mixing a whole bunch of recipes from others in the hopes that one will accidentally work. A methodical approach is far faster and more likely to produce a good product.

By 'adjustability' we mean you can alter the recipe to increase or decrease thermal expansion while not disturbing the glaze's visual properties or melting behavior. This gives you the ability to respond to any clay body. The best approach is to use a base recipe of 15 parts kaolin (EPK is best), 5 silica, and 80 of two or three balanced low melting borax frits having different expansions and 15% added zircon opacifier to make it white. Two frit examples are Ferro 3124 (expansion 7.7) and Ferro 3195 (expansion 7.1). Moderate shivering can be handled by simply increasing the amount of 3124 at the expense of 3195, crazing by increasing the amount of 3195 (frit 3195 also has a softer gloss). In the case of severe shivering, you can introduce a high expansion frit (such as Ferro 3134) or eliminate the silica, and for severe crazing increase the silica. Another thing worth mentioning is boron blue (see link to item in glossary). If you have this problem, increase the amount Al2O3 and reduce the CaO (frit 3195 is especially good for this).

Choosing a Clay

One of the most difficult aspects of the Majolica process is firing ware to an even defect-free glaze surface. While an extended firing schedule is one aspect of this, it is also important to choose a proper clay body. Classical ware was made from red-burning clay. It might seem odd to struggle to evenly cover a red terra cotta surface with a white glaze rather than just use a white burning clay. However at low temperatures red burning bodies are much stronger simply because they melt at lower temperatures.

Get a terra cotta clay that fires to a nice red at cone 03. Try firing it to cone 02, 1, 3, and 5 to verify that it is a true terra cotta. It should be near melting by cone 5 and transitioning to dark brown around cone 1. Also, make sure the material has a fine particle size at least 100 mesh and finer (if there are larger particles in the body pinholing can occur because the larger particles both produce gases of decomposition and collect them in surrounding voids). If you have an electronic kiln controller you can extend firing time and tolerate coarser clays better if necessary.

'Dependability' is another big factor in majolica glazes. While frits are more expensive they are much more consistent and produce better slurries than Gerstley Borate mixtures. In addition Gerstley Borate recipes usually have no clear adjustment strategy, and even if there is other properties of the glaze are often detrimentally affected. Since the clay-glaze interface in low fire ware is not nearly as good as stoneware, the glaze bond will fail much more readily in functional use. Glazes tending toward shivering can shed sharp-edged glaze flakes, a catastrophic event if ware is being used functionally. Glazes tending toward crazing will severely compromise ware strength. The very best thing you can do is make sure your glaze fits as well as possible. If possible, get the clay/glaze combination strength-tested to make sure the glaze fits, even if there is no visible problem.

Adjusting the Glaze

Make glaze text pieces and apply the glaze quite thick and fire to cone 06 and 04 and note the glaze's gloss and tendency to run. If it is running too much for cone 04, add a little kaolin (5%) to raise the melting temperature (if the glaze is also crazing add silica instead).

Perform a boil-ice test by immersing a fired glazed tile in ice water for five minutes, then boiling water for five minutes. Repeat this three or four times and check for crazing or shivering on each. If the glaze shivers keep increasing the higher expansion frit and redoing the test until it disappears. If you end up with all higher expansion frit, then remove the silica from the recipe and retest. If it still shivers begin introducing the super-high expansion frit (e.g. Ferro 3134). If the glaze crazes move in the opposite direction until all the frit is the lower expansion one. If it still crazes begin adding silica in 5% increments until the glaze does not melt properly. If it still crazes, fire higher and add more silica.

Low fire red clays often contain significant soluble salts that can deposit on the surface during drying, leaving an unsightly whitish scum and affecting the overlying glaze. Make sure your supplier is putting enough barium carbonate in the mix to precipitate these salts. Don't worry about barium leaching, it is under the glaze, it transforms to nontoxic barium sulfate during precipitation, and it participates in glass-building during the firing.

If necessary increase or decrease the amount of zircon opacifier if the glaze is either too white or not white enough.

Applying the Glaze

Glaze must be applied evenly and much thicker than for porcelain or stoneware. Getting a thick even coverage of glaze is critical for the Majolica process. Any variation of glaze thickness or thinning at the edges will expose the underlying red body color or impose a darker glaze color (in stoneware this is not nearly as big of a concern). You must do whatever it takes to achieve an even thickness whether it be mixing 10 gallons so you can dip, spraying it, waxing and glazing in two stages, heating the ware before glazing, gelling the glaze with a few drops of an acid like vinegar, sanding away the drips, etc. If you need to add gum to harden the glaze surface for handling, be sure that the gum is not countering gelling tendencies or slowing drying as this will make it much more difficult to get an even coverage.

To begin production, we recommend you get a 50 lb. bag of frit (about $100) and mix 5-10 gallons of white and transparent glaze. It is always better to dip the ware completely to get an even layer. If you don't have a pair of dipping tongs, be sure to get some.

The character of the glaze slurry is critical to achieving even coverage. Using at least 15% kaolin with good gelling properties is one method. We find that EPK works very well. Make the slurry viscous enough so that you can dip your finger and pull it out slowly without one drip falling off.

Dip ware into the glaze using dipping tongs. Pull it out carefully and the glaze should stay put and dry within seconds for thick ware and in a few minutes for thinner walled items.

If you possibly can get an electronic kiln controller. The success of low fire ware, especially Majolica depends heavily on being able to fire up slowly and hold the temperature. Consistency of ware time after time depends on being able to repeat the same firing curve.

Developing Colors

Obtain a selection of glaze stain powders recommended for cone 04 (in a pinch, you can also use copper carbonate for turquoise, cobalt for blue, and chrome for greens). Get a supply of foam cups, a teaspoon, and bag of the glaze developed above (minus the opacifier) to mix with the stains (some people use Gerstley borate). We will call this the 'melter' because many stain powders will not melt on their own. For each stain, take a foam cup and make an approximate 50:50 mix of the stain with the transparent melter. Add water and stir with your brush until it is a tempera paint consistency. Paint quick test-strokes on white glazed tiles. Cross some strokes to see what double thicknesses look like. With a fine brush paint the identification number of each stain using the stain mix itself. Fire the tiles.

Examine each color to determine if it is adequately melted. If not, increase the melter portion and test that color again. If any of the stains go on too dark or pasty, reduce the stain portion in favor of melter and retest. If any colors are not correct, it is possible that the chemistry of the melter conflicts with stain color development requirements (i.e. chrome-tin stains require the absence of zinc and at least 10% calcia, thus the Ferro frit 3134 above will not develop the pink if used alone in the glaze). Check documentation of the stains and compare with the chemical formula of your glaze recipe to solve these problems.

Paint some of each stain on a piece of bisque ware and apply the transparent version of the glaze over top (it does not need to be thick). Fire to see if the color develops properly. If any colors are not correct, again it is possible that the chemistry of the frit conflicts with stain requirements.

Matte Glazes at Low Temperature

Because melting is a big issue at low fire it is much more difficult to create a matte that is hard, smooth, and uncrazed. Generally however, it is possible to simply add whiting, talc, dolomite, magnesium carbonate (or a mix) to a glossy glaze. While these materials supply CaO and MgO fluxes at high temperatures, at low fire they are refractory and stiffen and opacify the melt and precipitate out if they do dissolve. Try up to 20% magnesium carbonate and then reduce it until you get a compromise between matteness and resistance to crawling. Likewise, additions of 20 parts of mixtures of dolomite and whiting, or talc and whiting, or even dolomite alone will work in some glazes. Also, it is helpful to have plenty of silica present to encourage the formation of silicate crystals with CaO and MgO. Generally you need to experiment to get the right amount. Matte glazes will not heal imperfections as well and they will crawl if thick so you need to be prepared to learn how to use a particular mix effectively.

G2805 is an interested example. Frit 3134 is a very fluid melting no alumina boron frit. The kaolin suspends and adds a little alumina. The high silica forms crystals with the dolomite and whiting.

G2805 Cone 04-06 Matte
Frit 3134  44
Dolomite    8
Kaolin     12
Whiting     8
Silica     28

Conclusion

Making the low fire process work requires considerable determination and testing, do not give up too easily. It is true that ware is not as strong as that fired at higher temperature, but it is also true that there is no other ceramic process that can give the same rich color and maintain the detail of even the finest brush strokes as low fire Majolica ware.

If you want to learn a lot more about glazes then check out our reference library. If you want power to create and change glazes you need INSIGHT software.

Related Information

Links

Oxides B2O3 - Boric Oxide
Glossary Majolica
Majolica is white opaque glazed red earthenware clay having colored overglaze decoration. But if you know more about what it is technically you will have more control of your product.
Troubles Glaze Crazing
Ask the right questions to analyse the real cause of glaze crazing. Do not just treat the symptoms, the real cause is thermal expansion mismatch with the body.
Materials Ferro Frit 3134
Articles Low Fire White Talc Casting Body Recipe
The classic white ball clay talc casting and modelling recipe has been used for many years. It is a dream to use as long as you are aware of the problems and risks.
Articles Where Do I Start?
Break your addiction to online recipes that don't work. Get control. Learn why glazes fire as they do. Why each material is used. Some chemistry. How to create perfect dipping and drying properties. Be empowered. Adjust recipes with issues rather than sta
Articles The Majolica Earthenware Process
How to make strong, durable functional ware from red terra cotta odies based on the traditional of majolica.
Articles The Potter's Prayer
A prayer for potters who wish to continue down the road of text book glaze recipes, never really getting what they want, never getting control.
Articles G1214M Cone 5-7 20x5 Glossy Base Glaze
This is a base transparent glaze recipe developed for cone 6. It is known as the 20x5 or 20 by 5 recipe. It is a simple 5 material at 20% each mix and it makes a good home base from which to rationalize adjustments.
Articles Variegating Glazes
This is an overview of the various mechanisms you can employ to make glazes dance with color, crystals, highlights, speckles, rivulets, etc.
Recipes G1916Q - Low Fire Highly-Expansion-Adjustable Transparent
An expansion-adjustable cone 04-02 transparent glaze made using three common Ferro frits (low and high expansion), it produces an easy-to-use slurry.

By Tony Hansen


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