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
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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
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Fixing a glaze that does not stay in suspension
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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
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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!
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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
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Making Glaze Testing Cones
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Outdoor Weather Resistant Ceramics
Overview of Paper Clay

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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
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Where Do I Start?
Why Textbook Glazes Are So Difficult

Painting Glazes Rather Than Dipping or Spraying

Description

Potters who are used to dipping and spraying glazes might be surprised to learn how well glazes can paint on if they have enough gum in the recipe.

Article

Likely you have had problems getting glazes to apply evenly when dipping ware. Many dipping glazes either dry too fast or too slow, drip or curtain during draining, settle out quickly, crack during drying or go on too thick or thin. In industry 'lay-down' is considered a big factor in the ability to fire a piece with an even glaze layer free of defects. On small or delicate ware it can be very difficult to achieve good laydown.

If you have ever used commercial glazes from Duncan or Mayco you know that although the idea of painting glaze onto ware can be quite strange to potters, it actually works very well. It is just about impossible to evenly paint a typical dipping glaze, they dry way too fast and just don't flow like paint. So how does Duncan or Spectrum make a glaze 'paintable'. The answer is gum. Lots of gum.

CMC gum, for example is an organic sodium carboxymethylcellulose (like a glue) that is normally employed to harden unfired ceramic glazes (cement the particles together) for safer handling of the ware. Although CMC gum is not intended as a suspending agent, amazingly it can do exactly that. You can actually make fritted glazes that contain almost zero clay content and suspend and harden them totally using gum.

A very nice side effect of the addition of gum is that glazes dry slower. In fact, you can tune the amount of gum in the mix to achieve the drying speed you want. It should paint and flow nicely but dry fairly quickly after laydown.

How much should you use and how do you put gum in a glaze? Powdered gum resists dispersion in water thus it is difficult to add it to an existing liquid batch. However if gum powder is mixed with other dry ingredients before adding them to the water it can be done (often 0.5-1.5%). A much more effective method is to boil water, add about 25-30 grams of powdered gum per litre and mix vigorously with a mechanical mixer. Normally this mixture is added during mixing to replace part of the water however I have found that for brushing it should be used to makeup the entire water complement. There is room to use 40 grams per liter if needed.

Amazingly, even though the gum solution is quite thick and syrupy, added powder mixes in very easily. The gum solution seems to wet the particle surfaces better than water alone.

Each glaze will paint a little differently. If you find that a glaze dries too quickly and does not flow enough try adding a little more water before deciding that the gum content is too low.

Consider some of the advantages of painting glazes:

Since CMC is an organic material there can be problems with microbial growth in your glazes. If this occurs, you can use a small amount of DettolĀ® (from the Pharmacy, actice substance chloroxylenol).

Related Information

Links

Materials CMC Gum
URLs cmc-salts.com/home.htm
All about CMC Gum

By Tony Hansen


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