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
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 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

The Right Chemistry for a Cone 6 MgO Matte

The image (link below) compares the chemistry and recipes of four high-MgO matte glazes. The glaze on the far right is the initiator, the one against which the others are being compared. It is G2928C, a cone 6 Ravenscrag Slip matte (R-Matte) developed from Moore's matte original (has some tin to whiten it). It is conservative (is not as matte as the two others to its left, but it does not cutlery mark). It has a low Si:Al ratio and maximum recommended MgO and quite a bit of KNaO. But I wanted to understand what the implications were of adding and removing SiO2 and Al2O3 in a magnesia matte, how much of a role does the MgO play. Well, it appears MgO is the key, the rest of the recipe can vary quite alot.

3728A is our original dolomite-testing recipe (Dolo-matte). It is 27% dolomite. It takes MgO to 0.4 molar and has very little KNaO. It has a stunning ivory surface, but cutlery marks. It has much lower SiO2 and half the Al2O3 yet does not flow more (because of the greater MgO and less potent CaO-dominant flux mix).

2934 is more matte than R-Matte. It has more MgO and CaO at the expense of KNaO and Si:Al (the Si:Al ratio is the same). Amazingly it is actually flowing better. It does not cutlery-mark. The color is darker than Dolo-matte because it is developing a more complete glass that gives depth.

2934A was done to see if MgO would matte a high silica version. The Al2O3 was dropped way down, the SiO2 taken upward for a ratio more than double R-Matte. You would think it would flow the same because the total Si+Al is actually less. But no. Does Al2O3 have to be high for this to work? No, Dolo-matte has low Al2O3. Is a low ratio needed? No Dolo-matte has a higher ratio that 2934 yet is more matte. Is significant KNaO needed? No, Dolo-matte and 2934 have very low KNaO.

So I think I know: You need lots of MgO, that is the magic. High or low Al2O3, but there is a SiO2 sweet-spot where a non-markable glass develops. You don't need a lot of boron, this only has 0.1 (some cone 6 glazes have 5 times that). I am going to put a little tin in 2934 and raise (yes, I said raise) the silica a little for just slightly more matte.

Related Information

Exporting insight-live recipes to a CSV file

An Insight-live page displaying four cone 6 matte recipes. It has been exported to a CSV file which I have opened in my spreadsheet software. I then reorganized it to compare these 4 glazes and relate the chemistry to the melt flow tests.

Links

Glossary Cutlery Marking
Ceramic glazes that mark from cutlery are either not properly melted (lack flux), melted too much (lacking SiO2 and Al2O3), or have a micro-abrasive surface that abrades metal from cutlery.
Recipes G2934 - Matte Glaze Base for Cone 6
A base MgO matte glaze recipe fires to a hard utilitarian surface and has very good working properties. Blend in the glossy if it is too matte.
Recipes G1214Z - Cone 6 Silky Matte
This glaze was born as a demonstration of how to use chemistry to convert a glossy cone 6 glaze into a matte.
Articles G1214Z Cone 6 Matte Base Glaze
This glaze was developed using the 1214W glossy as a starting point. This article overviews the types of matte glazes and rationalizes the method used to make this one.
Oxides MgO - Magnesium Oxide, Magnesia

By Tony Hansen


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