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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)
Can We Help You Fix a Specific Problem?
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
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 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 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 Ceramic Glazes
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

Glaze chemistry using a frit of approximate analysis


Many of the best frits do have a published chemistry, or the chemistry is approximate. Can we still use them in glaze chemistry? Yes.


Is this possible? Yes. How? Relativity is the key. Consider thermal expansion. Rather than try to predict absolute thermal expansions for specific chemistry profiles, it is more practical to try move the chemistry of a glaze in a specific direction to adjust the fired expansion. For example, a crazing glaze needs to have the thermal expansion reduced to reduce the crazing. A cycle of calculations and then physical testing will achieve the desired goal.

An effective strategy to stop crazing is to reduce the amount of KNaO in a recipe and substitute fluxing oxides of lower thermal expansion (like MgO, Li2O, CaO, Sro). Suppose a recipe contains a frit of approximate chemistry (where the frit company releases a chemistry that shows a range for each of the oxides rather than exact amounts) also contains significant feldspar and silica. Without touching the frit, we are in a position to reduce the feldspar and introduce materials that source the desired fluxing oxide(s) (and then add or remove clay and silica to rebalance the SiO2 and Al2O3 amounts). Even if the mystery frit contains KNaO it does not matter, its contribution will be constant, we are adjusting with other materials that also supply it. But there are a guideline or two to follow to make success more likely:

-You must maintain the same total for the recipe and the mystery frit amount also must remain unchanged.

-Compensate when adjusting material amounts where a significant LOI is involved. For example, whiting has a 50% loss on firing. That would mean that for every 1% calcium carbonate lost the recipe total drops by 0.5%. Watch the LOI that Insight calculates, keep the total minus the LOI the same as the original. For example, if the original glaze has a 10% LOI that means you only actually have 90% that goes into making the fired glaze. If you make changes that produce a recipe having a 95% LOI, the recipe total is now greater and the frit is proportionately less.

-In your calculations, use an average of the oxide ranges given for the frit as if it were the actual chemistry, this enables you to make better decisions about the most appropriate kinds of changes you could make to the chemistry to achieve the desired goal. Often the amount of the frit may be less than 30% and thus the calculation of the final chemistry of the glaze is not altogether inaccurate.

By Tony Hansen
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