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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
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 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

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

I have always done it this way!


If you are a potter and have gotten away with pushing the limits in your process for many years there will eventually be a day of reconing. That day could even be retroactive!


For every mile of highway there are two miles of ditch! If we compare ongoing production of ceramics to a highway, then many potters spend some time in the ditches with troubles. It is hard to accept a kiln load of warped, bloated, dunted or crazed ware or a drying rack of cracked pots.

Potters can be hard hit and others go bankrupt when unable to solve a problem. If you think you have a process or a clay body that enables breaking the rules, think again. Your margin for error, which prevents problems, is narrower. The nature of ceramics is that if you do your best and suppliers do their best there will still be problems because of variations you or no one can control.

Consider some viewpoints that can get you in trouble:

I've always done things the same and now there is a problem, it is not my fault
Have you really always done it this way? Are there changes you have overlooked? Is the way you have always done it the best way? If you have been "driving on the shoulder" by taking shortcuts in the forming, drying or firing process then is being in the ditch a surprise? Is it possible that no supply company can deliver the kind of consistency that your "push-the-envelope" process requires?

We are too busy, we don't have time to change our process
By understanding details of the process and optimizing accordingly industry has figured out how to fire ware in less than an hour cold-to-cold. Maybe you could analyze your situation and solve the problem and cut time. It is often better to work out the problem than start over with a new clay body. Of course, there are times when switching bodies is needed.

I'll worry about making the ware, the clay manufacturer can worry about keeping the clay consistent
First, are you paying due attention to 'making the ware'? Does your kiln fire evenly? Do you really know what temperature it fires to? Do you stress ware during drying? Do you stress test your glaze to make sure it won't craze and pieces won't crack on sudden heating or cooling? Clay body manufacturers cannot afford to take the view that material suppliers have everything under control (although some do), constant material and product testing is a must.

I don't need to know that technical stuff, just give me a good clay and glaze recipe and I'll do the rest
'Doing the rest' involves a lot. No the least of which is being sure that a glaze from one manufacturer fits the body made by another. Good bodies and glazes need a good process to make them work.

I've been potting for 20 years, I know what I am doing
Old habits die hard and can bring trouble. 50 year potters are much less certain about things. Depending heavily on a traditional but shaky technique will bring a day of reckoning.

Feedback on a social media site verified this is my problem

My glazes are crazing, they never did before
Glazes craze because their thermal expansion does not match the body. There is a lot of bad advice on this online, don't follow it. Any amount of crazing indicates a big problem. Lower the thermal expansion of a glaze or raise it in the body. Imagine realizing that all ware sold in the past is all going to craze for customers!

Understand the tradeoffs of your body and process? For example, vitreous bodies tend to warp or bloat on overfiring. Highly plastic ones tend to crack on drying. Porous functional ware bodies leak if the glaze does not fit. Low-silica or high-feldspar glazes often craze. Etc. Understanding your clay body and being in contact with the manufacturer is good. We are all going to weave on the one-way highway of ceramic production, but if you are near the middle you will stay out of the ditch.

Related Information

I have always done it this way. Why is it not working now?

Are you really sure the problem is with the materials? I had been using an 85% Ravenscrag, 15% frit glaze for many years with no crawling problems. But then it started crawling. I tried mixing with new materials and the old ones. Still crawled. The problem? What was I thinking? An 85% clay glaze is going to crawl so the question should have been: How did I get away with it for so long? I actually do not know! But I am now calcining Ravenscrag as appropriate (as documented at and I love the control this gives me in balancing slurry properties with drying hardness.

This always worked before. Why cracking now?

Glaze compression failure

This thrown piece has thin walls and a thick base. A thickly applied inside glaze. No glaze on the outside (showing off the beautiful red body color). These factors are a recipe for glaze compression failure. And that is what has happened! But this has worked for the potter in the past! So what is needed to continue doing this unrecommended technique and get away with it? Thicker walls. Thinner base. Thinner glaze application on the inside.

By Tony Hansen
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