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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

Concentrate on One Good Glaze
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 body using clays native to your area
Formulating a Clear Glaze Compatible with Chrome-Tin Stains
Formulating a Porcelain
Formulating Ash and Native-Material Glazes
G1214M Cone 5-7 20x5 glossy transparent glaze
G1214W Cone 6 transparent glaze
G1214Z Cone 6 matte glaze
G1916M Cone 06-04 transparent glaze
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
Glaze chemistry using a frit of approximate analysis
Glaze Recipes: Formulate and Make Your Own Instead
Glaze Types, Formulation and Application in the Tile Industry
Having Your Glaze Tested for Toxic Metal Release
High Gloss Glazes
Hire Me to Fix a Specific Problem
Hire Us for a 3D Printing Project
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
I have always done it this way!
Inkjet Decoration of Ceramic Tiles
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
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
Painting Glazes Rather Than Dipping or Spraying
Particle Size Distribution of Ceramic Powders
Porcelain Tile, Vitrified 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
Simple Physical Testing of Clays
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 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
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 in understanding glazes?
Why Textbook Glazes Are So Difficult
Working with children

Chemistry vs. Matrix Blending to Create Glazes from Native Materials


Is it better to do trial and error line and matrix blending of materials to formulate glazes or is it better to use glaze chemistry right from the start?


Suppose you have a material native to your area and want to create a pottery glaze using it. You want to maximize the amount used in the recipe. Popular wisdom suggests doing a matrix of blends with materials like feldspar, silica, kaolin, calcium carbonate, etc. Let's compare this method to a chemistry-assisted approach (one where we start at an existing recipe and move its firing properties in a certain direction using discretionary changes to its chemistry).

A glaze is much more than 'looks'. There may be ten blends that look OK on small test tiles, but only one that functions well. Function? That is about hardness, resistance to leaching, fitting your clay body, suspension and application properties, compatibility with coloring oxides, tendency to devitrify, blister, crawl, cloud, run, etc. Fixing these issues in a blend-created recipe almost always compromises the appearance. Consider crazing: It happens because of high thermal expansion, generally imparted by high Na2O or K2O in the chemistry. These come from feldspar. Where do all those high-feldspar recipes online come from? Feldspar was one of the corners on the triaxial blend and all the best-looking glazes were close to that corner!

Chemistry looks at a glaze as a formula-of-oxides. There is a direct link between how it fires and that chemistry. The materials in the recipe are thus oxide sources. Looking at glazes this way enables the use of limit formulas. Frits find a comfortable home in this approach, they are keys to melting glazes at middle and low temperatures.

Consider an example: A volcanic ash that I dug from a local quarry near Elkwater, Alberta. I had it analyzed at a lab. I converted the analysis to a unity formula using desktop Insight.

  CaO    8.7% 0.86 molar
  Na2O   0.1  0.11
  K2O    0.3  0.02
  Fe2O3  1.1  0.04
  MgO    0.8  0.11
  SiO2  78.7  7.29
  Al2O3  2.2  0.12
  LOI   14.0

Notice how low the Al2O3 is. And the SiO2 is very high. The silica:alumina ratio is thus 60:1 (a glaze is typically 10:1). So I don't want to blend this with materials that add more silica but I do want ones that add alumina. That eliminates feldspar! Kaolin fits the bill. And it will suspend the slurry, a real bonus.

This ash has a high CaO content quite a bit higher than a typical glaze (this is coupled with being very low in other fluxes). That means I need to add materials sourcing fluxes other than CaO. That excludes calcium carbonate and dolomite (imagine the waste of time it would have been to triaxial blend this ash with calcium carbonate and feldspar!).

As it turns out, it is possible to use up to 60% of this ash in a glaze to melt around cone 7 (the lesson link below, although dated and using the old desktop Insight software, demonstrates the principles of this). So, for this project, chemistry belonged at step one. Any blending would be to fine-tune things after that! One great comment I saw on Facebook by Paul Haigh was: "Chemistry guides, experiment decides".

There is an elephant in the room here: Firing. Potters generally seek reactive glazes and the firing schedule is often the key to the way they fire. But still, their chemistry still provides the main way to explains the results.

Related Information


Projects Oxides
Projects Materials
Glossary Wood Ash Glaze
Common washed wood ash can supply important ceramic oxides when melted, so it can comprise significant percentages in a recipe. Plus it can produce unique visual effects.
Glossary Feldspar Glazes
Feldspar is a natural mineral that, by itself, is the most similar to a high temperature stoneware glaze. Thus it is common to see alot of it in glaze recipes. Actually, too much.
Glossary Glaze Chemistry
Glaze chemistry is the study of how the oxide chemistry of glazes relate to the way they fire. It accounts for color, surface, hardness, texture, melting temperature, thermal expansion, etc.
Glossary Triaxial Glaze Blending
In ceramics many technicians develop and adjust glazes by blending two, three or even four l materials or glazes together to obtain new effects
Glossary Native Clay
A clay that a potter finds, tests and learns to process and use himself. To reduce the costs of importing materials manufacturers, especially in Asia, often develop processes for clays mined in their locality.
Media Desktop Insight 4 - Add a Native Material to MDT, Build a Glaze
Learn to add a native volcanic ash to the INSIGHT materials database (MDT) and then create a glaze from it maximizing its percentage. Learn to impose an LOI on a material and why this method is better than line blending.
By Tony Hansen
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