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

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
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

Ball Milling Glazes, Bodies, Engobes

Description

Industries ball mill their glazes, engobes and even bodies as standard practice. Yet few potters even have a ball mill or know what one is.

Article

A true ball mill is a porcelain jar partly filled with spherical or rounded cylindrical porcelain balls. Industrial versions are made of metal and have porcelain linings. Small scale operations most commonly employ ball mills for grinding glazes. The suspension is poured in, a lid secured, and it is rotated on a motorized rack, sometimes for many hours. The tumbling balls within grind particles smaller and smaller as they impact each other (and crush particles that happen to be at the points of contact). The creamier glaze that milling produces applies better, has more stable viscosity, fires more consistently and cleaner with less specks and imperfections (eg. pinholes and blisters), and melts better. Glazes can be overmilled, this can produce solubility, crawling, opacification and slurry issues (since certain materials in the glaze need to be kept above a certain particle size to behave correctly).

Potters and hobbyists are generally not aware of the importance of the ball mill to industrial ceramic ware production. For a small-scale stoneware operation it is possible to survive without one using a narrow range of glazes and techniques. But when production is ramped up consistency, reliability of the glaze appearance and defect free ware become paramount. Many materials in ceramics are simply not ground fine enough for glazes (they produce fired specks or defects related to expulsion of gases around larger particles); ball, native and slip clays are an example. In other materials fine particles agglomerate into larger ones (e.g. barium carbonate, tin oxide, wollastonite). Others are supplied as a grain-type material rather than a powder and obviously have to be milled (eg. lithium carbonate, alumina hydrate). Engobes that must be sprayed, sink screened or even inkjet printed must be ball milled or nozzles will clog and screen will blind. Obviously, bottled engobes and glazes that potter's buy are ball milled when produced.

Amazingly, many industries routinely grind their body materials in ball mills (e.g. the insulator and even tile industries). One Kalemaden plant we visited in Canakkale, Turkey (one of the largest in the world) airfloats and mills local clays for all their products. They even collect their own flint rocks and break and mill them to round. Companies may be seeking residues of less than 0.1% on 325 mesh. Other benefits also ensue, including more plasticity, better fired maturity and strength. The benefits are not only very high quality and defect defect-free products, but better consistency. Typically a slurry of 65% clay and 35% water is made (only possible if deflocculated) and ball milled, then dewatered (using filter presses, spray driers, etc) to make powder or pellets. In addition, materials will melt or go into solution in the melting glaze significantly better or sooner if they are ground finer.

Ball mill jars need to be heavy and thick to withstand use. They are expensive, a 1 gallon jar typically costs about $100 US. These jars are not easy to make. They must have a water tight lid and be a true cylinder (or they won't rotate without jumping on the rack). Jars are not glazed on the inside. Lighter duty jars are best made by casting a low shrinkage porcelain. Heavy duty ones must be made using some type of turning process that produces an accurately vertical and round sidewall. It would be extremely difficult or maybe impossible to dry and fire a suitable thick jar made by throwing a cylinder shape from a plastic porcelain. Plastic jars are an option for studio use. The grinding action between the jar walls and balls is lost but the balls will still crush the particles between them if you mill for longer periods. Plastic mill jars also run much quieter. Typically small jars have a range of ball diameters from 1-4 cm. The pebbles cost about $6 US per pound and you need about 8-10 lbs for a 1 gallon jar.

A small mill rack is $700-1300 US. However you can build your own (see the links here). href="https://www.digitalfire.com/gerstleyborate/ballmill/">https://www.digitalfire.com/gerstleyborate/ballmill/
Or you google the booklet "Thoroughly Modern Milling" by Steve Harrison (it is intended to assist the potter in building a ball mill with a roller mechanism to handle a jar in the 3 to 5 gallon range). The text describes how to assemble the parts illustrated in the detail drawings and briefly describes making your own jar and ball from porcelain clay body. A4 size, 6 pages of text and 6 x A3 pages of detail mechanical drawings. There is one color photograph.

If you are using a ball mill in your operation resist the temptation to think that using one is just a matter of throwing in some pebbles, pouring in the glaze, and turning it on for an hour or so. As a general rule you should mill for the same amount of time, fill the jar to the same level, use the same charge of pebbles and the range of sizes of the pebbles should be controlled (the pebbles wear down over time). There are many finer points to know about using ball mills and industry uses the term "mill practice" to embody them. Variation caused by poor mill practice can create a number of significant fired glaze faults and affect slurry and application properties. To learn more check the book 'Ceramics Glaze Technology'. You should be able to find a copy at one of the used ceramic book vendors or information online.

Related Information

Make your own ball mill rack - Front side

Links

Articles Glaze Recipes: Formulate Your Own Instead
The only way you will ever get the glaze you really need is to formulate your own. The longer you stay on the glaze recipe treadmill the more time you waste.
Articles Formulating Ash and Native-Material Glazes
How to have a volcanic ash analysed and them use ceramic chemistry to create a glaze that contains the maximum possible amount of the ash for the desired effect
Articles Make Your Own Ball Mill Stand
Pictures of a ball mill rack that you can make yourself
URLs http://www.wecreate4u.net/dwilliams/mill/mill.html
Another home made ball mill rack
URLs http://www.unitednuclear.com/mills.htm
Ball Mills from United Nuclear
Glossary Ball milling
A method of grinding particles in ceramic powders and slurries. A porcelain vessel filled with porcelain pebbles tumbles and particles are ground between colliding pebbles.

By Tony Hansen


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