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

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 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
What is the Glaze Dragon?
Where Do I Start?
Why Textbook Glazes Are So Difficult

Creating Your Own Budget Glaze

Description

How to take a stockroom full of unused materials and turn them into a good glaze rather than try umpteen online recipes that require buying yet more materials you do not need and do not work.

Article

You have probably noticed that there are not many rich potters. Money, or the lack of it, is always a major concern at art schools and college ceramics departments. Little wonder then that it is always important to make the most efficient use of equipment and materials at hand. Glaze materials, as everyone knows, can be very expensive. Do the expensive materials produce better glazes? Not always. Often the key is the engineering that goes into the formulation.

I participated in a fascinating example of saving some money, and would like to relate it to you. Although this is very "small scale", I'm using it to demonstrate principles applicable t any operation. Many companies have hundreds of tons of materials they would love to be able to use up in products. For others, the amounts are modest but the challenge is there, especially if there are quite a few different material types.

A new instructor took over a long neglected school ceramics program. She was on a tight budget but inherited a small inventory of assorted glaze materials to work with. She secured suitable glaze recipes but found little commonality between the materials called for in these recipes and the ones on hand. Thus it appeared that mixing the new recipes would actually increase the existing inventory of raw materials. Such a cost seemed unjustified and wasteful.

Then there is the perennial problem of textbook glazes being poor travelers. After all, circumstances vary. Most potters, for instance, will confirm that they have to test hundreds of recipes to find one whose touchy nature they can just tolerate. Likewise, in industries that mix their own glazes, those which function well in one plant produce problems in others. So many technicians have found it easier to just design a glaze from scratch.

What's the best approach? You guessed it: Calculation followed by 'trial and error work' to refine a final recipe. With a little simple guidance, it is really quite easy to create a working glaze after two or three trials! Getting back to our example; here is the inventory of materials that was on hand at the school.

The Inventory of Materials 

ZINC OXIDE         100 gs 
CALCIUM BORATE     1 kg  
CUSTER FELDSPAR    500 gs 
KAOLIN             2 kg  
SILICA             2 kg  
NEPHELINE SYENITE  500 gs 
WHITING            2 kg 
DOLOMITE           2 kg 
BALL CLAY          2 kg

I decided it was best to create a clear base glaze, which could be opacified to make white or colored with stains and oxides to make colored glazes. A large powdered batch could be mixed and easily blended with colorants. So I threw all the remaining materials together into one mix! No, not literally, but in Digitalfire Desktop INSIGHT.

Here is the result.

CUSTER FELDSPAR.....  .5
KAOLIN.............. 2.0
SILICA.............. 2.0
NEPHELINE SYENITE...  .5
ZINC OXIDE..........  .1
GERSTLEY BORATE..... 1.0
WHITING............. 2.0
DOLOMITE............ 2.0
BALL CLAY........... 2.0
                    ----
                    12.1
 FORMULA & ANALYSIS
 ------------------
 *CaO   .68  20.04%
 *MgO   .22   4.65%
 *K2O   .02    .96%
 *Na2O  .05   1.74%
 *ZnO   .02   1.05%
 *Fe2O3 .00    .18%
 *TiO2  .01    .32%
 B2O3   .15   5.48%
 Al2O3  .32  17.11%
 SiO2  1.53  48.48%
 RATIO 4.82

Check the links below to learn more about limit (or target) formulas. Using one of the charts as a target, it is quite simple to determine what oxides need adjustment to make the glaze melt better at a specific temperature. Below is an example of a limit chart. The normal limits for cone 6 glazes are shown (if B2O3 glass is glazes melt alot better and Al2O3 and SiO2 can be higher).

LEADLESS GLAZE LIMIT FORMULAS
(For a variety of temperatures)

Temp C 880 980 1080 1180 1280
Oxide Cone 012 08-05 04-02 3-7 8-10
CaO .15-.5 .15-.5 .3-.6 .3-.6 .35-.7
ZnO -.05 .05-.15 .1-.15 .1-.25 -.3
BaO -.1 .1-.2 .1-.2 .1-.3 -.3
MgO -.1 .075-.15 .1-.15 .1-.2 -.35
KNaO (Alkalies) .35-.5 .35-.5 .3-.5 .2-.5 .2-.45
B2O3 .8-1.5 .6-1.0 .5-.85 .3-.5 -.3
Al2O3 .1-.15 .15-.25 .15-.3 .2-.35 .3-.55
SiO2 1.25-2 1.5-2.5 1.75-3 2.5-3.5 3-5

The glaze already proposed has a nice selection of fluxes and appears good, except for a little too much CaO and a lack of SiO2 . Here is a recalculation, after the addition of enough silica to bring the SiO2 content up past the 2.5 minimum.

CUSTER FELDSPAR.....  .5
KAOLIN.............. 2.0
SILICA.............. 6.0
NEPHELINE SYENITE...  .5
ZINC OXIDE..........  .1
GERSTLEY BORATE..... 1.0
WHITING............. 2.0
DOLOMITE............ 2.0
BALL CLAY........... 2.0

FORMULA & ANALYSIS
==================
*CaO   .68 14.11%
*MgO   .22  3.27%
*K2O   .02   .68%
*Na2O  .05  1.22%
*ZnO   .02   .74%
*Fe2O3 .00   .13%
*TiO2  .01   .22%
B2O3   .15  3.86%
Al2O3  .32 12.05%
SiO2  2.85 63.71%
RATIO    8.99
WEIGHT 268.55

This brings the ratio up to 9, giving a glaze which should not be too matte or too glossy. Since there is such a variety of other fluxes, I left the CaO alone. The formula is now quite typical of a cone 6 glaze and further tests indicated that, yes, it does perform quite nicely as a silky matte at cone 6 and as a glossy at cone 7 and 8.

So, all the school had to do was buy 4 kilograms of inexpensive silica It resulted in enough to make more than 5 gallons of glaze, leaving money in the budget for extra clay for the children so they could use up all that glaze.

Most people would never try an approach like this. But I have outlined this simple experience to demonstrate a principle that has merit: It is often quicker, cheaper, and easier to design a glaze from scratch than test online undocumented glaze recipe that usually do not work (because of a variety of factors in your studio that differ from that of the author of the glaze). The ability to mix materials and predict the fired product by quick calculation is a big factor in being able to do this. Although this situation could have been more complicated and more materials might have been needed to produce a balanced oxide formula, the principles would have been the same. However, if there is a wide selection of materials, you will find this method will frequently succeed as it has here, requiring the purchase of only one or two materials.

Related Information

A limit or target glaze formula. What does this mean?

Recipes show us the materials in a glaze but formulas list oxide molecules and their comparative quantities. Oxides construct the fired glass. The kiln de-constructs ceramic materials to get the oxides, discards the carbon, sulfur, etc. and builds the glass from the rest. You can view glazes as recipes-of-materials or as formulas-of-oxides. Why use formulas? Because there is a direct relationship between the properties a fired glaze has (e.g. melting range, gloss, thermal expansion, hardness, durability, color response, etc) and the oxides it contains (links between firing and recipe are much less direct). There are 8-10 oxides to know about (vs. hundreds of materials). From the formula viewpoint materials are sources-of-oxides. While there are other factors besides pure chemistry that determine how a glaze fires, none is as important. Insight-live automatically shows you the formulas of your recipes and enables comparing them side-by-side. Click the "Target Formula" link (on this post at digitalfire.com) to see what each oxide does.

Links

Glossary Limit Formula
A way of establishing guideline for each oxide in the chemistry for different ceramic glaze types. Understanding the roles of each oxide and the limits of this approach are a key to effectively using these guidelines.
Articles Limit Formulas and Target Formulas
Glaze chemistries for each type of glaze have a typical look to them that enables us to spot ones that are non-typical. Limit and target formulas are useful to us if we keep in perspective their proper use.

By Tony Hansen


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