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
Trafficking in Glaze Recipes

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

Understanding Ceramic Materials


Ceramic materials are not just powders, they have a physical presence that make each unique and amazing. We cannot adequately describe the properties using just numbers, thinking in terms of generic materials is a key.


When you first started in ceramics, you were probably amazed at the array of exotically named raw materials. At that time, they were just white powders that were weighed out to match the recipes on hand. There were so many materials that it seemed impossible to ever understand the function of all of them. Our instructors often ignored their individuality, focusing only on the fired visual and tactile properties of 'mysterious' mixes of them.

You probably noticed that textbooks sometimes contain a separate section dedicated to describing major raw materials. They invariably classified materials according to major groups and this simplifies understanding the individuals. Like many people, you may have hurriedly skipped these parts for the more interesting 'how-to' chapters. It didn't take long to find out that some textbooks on ceramics did not even describe basic materials like kaolin; others were narrow in their treatment of it. Some like Hamer's "Dictionary of Materials" are much better.

Now that you are learning the oxide viewpoint, materials will take on a whole new life. They become "sources of oxides". However, as we have seen, materials have a chemistry, a mineralogy, and a host of physical properties to recon with.

Consider the following as typical of what you would often get from a supplier if you asked for information on a material like Barnard Slip:

CaO 0.57, K2O 1.14%, MgO 0.68%, Na2O 0.57%, TiO2 0.23%,
Al2O3 7.60%, SiO2 47.01%, Fe2O3 33.90%, LOI 8.31%

They can give you plenty of other numbers also (numbers that are often inaccurate and out-of-date). What do these number this tell us? To be honest, very little! Is it really a clay? Is it plastic? Is the SiO2 combined with alumina and others or is it in the form of quartz particles? When does it melt? What is the particle size? What is the raw color? How is it possible for a clay to have such high iron? What really is this stuff mineralogically? Is it synthetic? Is it similar to yellow ochre? Is it practical for use in clay bodies? Where can I get it? Is it available in different grades and from multiple manufacturers?

If you are like me, you want practical information; you want to know what a material is. We need to know enough to be able to ask some intelligent questions. The materials area on this site database is addressing these very issues. Efforts are under way to accumulate the kind of information people want from manufacturers and to standardize the way it is presented.

Barnard Slip is an interesting example. Since I have not received a data sheet from a supplier I simply tested it myself. The results of this testing can be found in the Digitalfire Reference Library.

This is not an ad, it is part of this article!

This is the kind of information we need about materials, isn't it?

Let's consider kaolin. This is quite different. There are hundreds available. In this case, we need a textbook description of what generic kaolin is, what it is used for, and why it is used in preference to other materials. It is much more than a simple source of Al 2O3 in glazes. Kaolin is the only practical source that does not bring fluxes also and that it is ideal because it is inexpensive, consistent, and imparts suspension and raw hardness properties. It is a popular body constituent because of its whiteness in comparison with ball clay and bentonite. Kaolin has a much larger particle size than either and its use improves drying performance by reducing drying shrinkage, enhances water penetration, and reduces fired shrinkage. Kaolins vary widely in their plasticity and they do not introduce soluble salts and coal the way ball clays do.

The key to wrapping your mind around the dizzying host of raw materials available is to learn them generically so that you can better evaluate the strengths and weaknesses specific name brands. Try to build first hand experience with a benchmark material of each type then relate the properties of new materials to those of the benchmark. In this way, you will develop flexibility and be able to become increasingly independent and capable.

In the materials area of this site we have adopted this concept of generic materials. Look up a material like kaolin, dolomite, feldspar, etc. to see an example. In time we will assign each generic description to an expert (or group of experts) in the field for maintenance. All name-brand materials will then be described in terms of the generics.

Related Information

An example of a material report at the Digitalfire Reference Library

Many of the materials listed are not described well or at all by their manufacturers. This is an example of where we had to do our home work, researching and rationalizing it to determine what information is likely more and less reliable. In many cases we simply do testing in our own lab.


Projects Minerals

By Tony Hansen

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