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

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
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
Formulating a Clear Glaze Compatible with Chrome-Tin Stains
Formulating a Porcelain
Formulating Ash and Native-Material Glazes
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 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 Black Art of Drying Ceramics Without Cracks
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
Using Plaster Bats
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

An Overview of Ceramic Stains

Description

Understanding the advantages of disadvantages of stains vs. oxide colors is the key to choosing the best approach

Article

Stains are fired blends of metal and ceramic oxides that have been reground into a fine powder. Stains containing otherwise toxic oxides can be employed without significant dangers. This is the first aspect of something that stains have that coloring oxides don't: stability. A second aspect of stability is that stains produce much more consistent and repeatable color than using raw oxide colors.

Stains are most popular at lower temperatures where colors tend to be brighter. However most stains can be used right up to high fire. Premixed low fire glazes are typically made by blending stains and commercial frits and other than following firing instructions, users of these products give little thought to the technical challenges that were overcome to produce them. This is a third key advantage of stains: the ability to target a specific color. Many ceramic color shades (i.e. reds) are difficult to achieve and beyond the abilities of end users.

While many stains are 'standard' and their composition is well known across the industry, others are proprietary. Stain companies don't release the exact makeup of stains but they do tell us the 'system'. For example, a green stain might contain chrome, cobalt and silica and be labeled 'CrCoSi'. Although silica is not a colorant itself, it is included to create a stable silicate crystal structure with the other two.

Stain companies often supply multiple products to produce a given color using different oxide systems (i.e. chrome-tin pink, manganese-alumina pink). Various factors like the base glaze chemistry, color shade, temperature, and end use determine the system you should choose. Knowing how to calculate the oxide makeup of a glaze or dealing with a stain company that provides good service are key factor to being able to troubleshoot color problems with stains.

Thus stains do not come with a 'unconditional color guarantee'. The shade produced depends on many of factors including the host glaze chemistry, on/over/underglaze use, glaze thickness, amount of opacifier, firing temperature, etc. Achieving colors with stains is certainly easier, but it is not a 'no-brainer'. Certain systems are quite flexible and produce color in many kinds of glazes (ie. cobalt silicate). Other systems either require that certain oxides be present in the host glaze in minimum amounts or others not be present at all. The symbiosis of host glaze chemistry and stain, for example, can be demonstrated with chrome-tin stains. They will not develop color if zinc is present or if there is inadequate calcia. It is common to hear people say that their pink stain 'burned out', but generally the stain is being used in an incompatible glaze base. Another interesting demonstration of these factors is the color chart of a typical stain company. These charts show the stain used in one or more fritted base glazes that are selected to be compatible with as many of the colors as possible. Certain samples will also have added opacifier and zinc, for example.

Admittedly, stains can produce homogeneous color which can be less interesting than the variegated and speckled color effects that can be achieved with raw metal oxides like iron, cobalt, copper, etc. But for manufacturing, it cannot be ignored that stains are far more consistent and reliable to use. Still, variegating agents can be added (like titanium and rutile).

Potters love to paint stains over and under glazes to decorate ware. Majolica ware is a good example. However, stains are refractory, they resist allowing overlying glazes to envelope the particles and then fasten onto the underlying body. Stains used for underglaze decoration, for example, need to be mixed with a recipe of materials into which they can melt and suspend, one that melts enough to attach to the body but not so much so as to bleed excessively into the overlying glaze. Different stain types require mediums of different chemistry, ones that enable the color development and have the proper degree-of-melt. Some stains tend to crystallize the surface if used overglaze. Likewise, if stains are used underglaze they vary in their willingness to allow the overglaze to penetrate through to form and interface with the body. Stains don't suspend well in water to create a paintable material either so it is necessary to mix them with something that will suspend the particles, slow down the drying and harden when dried.

Stains exist either in the context of the huge industrial ceramic industry or in the hobby, pottery, and ceramics markets. Large industries either have in-house technical people or contract consultants. Small users do not have this luxury. They should know that certain stain companies, (i.e. Mason) have developed excellent reputations for dealing with smaller volumes and providing support.

A fired glaze can leach heavy metals whether these metals are sourced from a stain or from raw metal oxides. Stains are made from the same metal oxides you would use to get the color, they have simply been prefired and blended for specific colors and often mixed with other materials to make them melt higher or leach less. Thus you should have your glazes tested for leaching if you are making functional ware having stained food surfaces. Better yet, use a liner glaze. There are many factors that determine if a glaze is leachable (for more information see the links on this page).

Why you should not paint pure stain powders over glaze

Why you should not paint pure stain powders over glaze

On the left is a pure blue stain, on the right a green one. Obviously, the green is much more refractory. On the other hand, the green just sits on the surface as a dry, unmelted layer. For this type of work, stains need to be mixed into a glaze-like recipe of compatible chemistry (a medium) to create a good, paintable color. The blue is powerful, it would only need to comprise 5-10% of the recipe total. Its medium would need to have a stiffer melt (so the cobalt fluxes it to the desired degree of melt fluidity). A higher percentage of the green stain is needed, perhaps double. It's medium needs much more melt fluidity since the stain is refractory. Of course, only repeated testing would get them just right. Guidelines of the stain manufacturer for chemistry compatibility need to be consulted also (as certain stains will not develop their color unless their glaze medium host has a compatible chemistry). And, to be as paintable as possible, use use a gum-solution/water mix (e.g. 2 parts water to one part gum solution).

Links

Articles How to Liner-Glaze a Mug
A step-by-step process to put a liner glaze in a mug that meets in a perfect line with the outside glaze at the rim.
Articles Glaze and Body Pigments and Stains in the Ceramic Tile Industry
A complete discussion of how ceramic pigments and stains are manufactured and used in the tile industry. It includes theory, types, colors, opacification, processing, particles size, testing information.
Articles Getting the Glaze Color You Want: Working With Stains
There are many things to know about to make the best use of stains, but one often ignored aspect is the relationship between glaze color and chemistry. If you want to control color you need to know about stains and chemistry.
Articles Is Your Fired Ware Safe?
Glazed ware can be a safety hazard to end users because it may leach metals into food and drink, it could harbor bacteria and it could flake of in knife-edged pieces.
Articles Having Your Glaze Tested for Toxic Metal Release
Having Your Glaze Tested for Metal Release
Articles Are Your Glazes Food Safe or are They Leachable?
Many potters do not think about leaching, but times are changing. What is the chemistry of stability? There are simple ways to check for leaching, and fix crazing.
URLs http://www.masoncolor.com/ceramic_RefGuide.asp
Mason Color Reference Guide
Glossary Ceramic Stain
Ceramic stains are manufactured powders. They are used as an alternative to employing metal oxide powders and have many advantages.
Projects Stains
Oxides MnO2 - Manganese Dioxide
Recipes G2853B - Cone 04 Clear Ravenscrag School Glaze
A Ravenscrag Slip base made by simply mixing it 50:50 with a frit
Materials Stain

By Tony Hansen


Tell Us How to Improve This Page

Or ask a question and we will alter this page to better answer it.

Email Address

Name

Subject

Message


Upload picture


Copyright 2008, 2015, 2017 https://digitalfire.com, All Rights Reserved