Glaze software - Recipe to Formula

The advent of computers now makes it possible for studio potters and ceramic artists to approach glaze experimentation from an analytical viewpoint focusing on the chemistry of the raw materials and the fired glaze.

Since the late 1980's various software packages have been developed internationally. At Dunedin, New Zealand's School of Art a program called Matrix was created by Lawrence Ewing to assist students in their glaze chemistry work. Since that time Matrix has grown to become a leading international glaze software package.

This lesson introduces this software, focuses on the entering and saving of a recipe, and discusses the concept of Unity Formula (also called Seger formula or emperical formula).

Summary of Concepts

The following list of concepts are discussed in detail in the Lesson Notes below.

• Glaze software is essentially used to generate a unity (Seger, emperical) formula for a recipe based on the chemical analysis of the raw materials in the software's databases.
• Matrix consists of 5 environments - work areas which focus on particular functions of the software.
• The unity formula is generated from the oxide analysis or unity formula for each of the raw materials in the glaze recipe.
• While the recipe represents the pre-fired form of a glaze the unity formula describes the analysis of the fired glaze.
• The term Recipe to Formula refers to the conversion of a list of raw materials and quantities to a unity or Seger formula.
• This process is based on the analysis of individual raw materials stored in collections or databases of raw materials on a computer's hard drive.
• A unity formula is the list of oxides that would be found in the chemical analysis of a fired glaze. The values for each oxide represent the proportional relationships of the oxides in the unity formula.
• In most glaze software programs an entered recipe can be saved on the computer's hard drive or to a floppy disc and the recipe and formula can be printed as a hard copy.
• A "Saved" recipe can be retrieved or loaded from the hard drive for reference or manipulation on screen.

Summary of Activities

This summary outlines the practical exercises associated with this lesson. They are described more fully in the Activities section below.

Study the following sections in the Help system of Matrix. (The following links open in a new browser window.)

• Quick Start - Enter and Save a Recipe
• Recipe to Formula
  • Overview
  • Entering a New Recipe
  • Clearing Displayed Recipe Data
  • Saving a Recipe
  • Printing a Displayed Recipe.
  • Loading an Individual Recipe.

• Entering your collection of recipes into Matrix and save them as individual files in the Individual Recipes folder.
• Enter two C.10 recipes and compare their unity formulae.
• Compare a C.10 and a C.6 recipes in Matrix's Recipe to Formula environment.
• Work through GlazeTeach Unit 4 - The Unity Formula

Equipment and Materials Required

• Matrix Glaze Calculation Software.

	Lesson Notes

Please study the following notes and supplement the information with readings from your books, magazines and internet resources.

For discussions involving Matrix please read the relevant sections of the Matrix Help file which may be access by clicking the help button while using Matrix or from within these lecture notes. Matrix Help files may also be viewed from the Matrix2000 website www.Matrix2000.co.nz.

Click here to open Matrix Help File.

Feel free to email lewing@woosh.co.nz if you need further explanation or wish to make comment.

A unity formula is a method of setting out in lists the chemical formula of a glaze or raw material's constituent oxides. Using this method the balance of flux, stabiliser and glass-former oxides can be quickly assessed even though the composition may be complex. Unity formulae assists the comparison of one glaze with another for the purposes of predicting effects and making adjustments.

Whatever materials are used to produce a glaze, the result is a combination of oxides. These oxides can be placed in three groups according to their "role" in a glaze melt (flux, stabiliser, glass-former).

The unity formula uses these groupings and brings the total of molecules in the flux group to unity. It then expresses the other two groups (stabiliser and glass-former) in ratio to the flux group.

The unity formula is usually set out either in three columns:

or in one column with divisions to seperate flux, stabiliser and glass-former oxides. This is the display method used in Matrix and throughout this course:

The unity formula expresses ratios between numbers of molecules. The actual number of molecules involved in a glaze are millions of millions. These vast numbers are conveniently scaled down in the unity formula. As a result the unity formula invariably includes some theoretical fractions of molecules.

The five working environment of Matrix are: Recipe to Formula - recipes are entered or altered and unity formulae are generated Formula to Recipe - formulae can be entered or altered from which recipes can be generated Blends - blends of various kinds can be generated based on glazes entered and saved in the Recipe to Formula environment Raw Materials - materials can be examined or entered into Matrix's databases or existing materials may be edited. Colourants - colourant materials can be examined or entered into Matrix's databases or existing colourant materials may be edited.

Click here for more information about Matrix's working environments.

Initially in this course we will work in the Recipe to Formula environment

Matrix (and all other glaze calculation computer programmes) operates from databases (lists) of raw material analyses. Using these raw material analyses the unity formula for a collection of raw materials and quantities (a recipe) can be calculated.

While these calculations are not difficult and can be done by hand, they can be long and prone to error. A computer programme does the calculation almost instantly thus making the unity formula perspective of a glaze very accessible with all the advantages it provides.

If you would like to know more about how the unity calculation is done click here.

A recipe is a list of materials and quantities. Each of those materials can be represented as a list of component oxides or oxides that will end up in the fired glaze.

The unity formula is a device which enables the easy comparison of the chemistry of one glaze with another. The following tables show two recipes which, apart from Silica consist of different sets of materials. However when these recipes are reduced to their unity formulae we find that their chemical composition is the same. i.e. When these different sets of materials are fired the chemistry of the resulting glass is virtually identical.

The study of unity formula is the study of the fired glaze.

Matrix uses its set of raw material analyses (over 700) to determine the chemical composition of a fired glaze. As each raw material and quantity of a recipe is entered into the software Matrix searches its databases to obtain the chemical composition of the material and calculated the unity formula for the entered materials.

The following image is the main Matrix window in Recipe to Formula mode. The window is expanded to show the two recipes in the tables above and their respective (identical) unity formulae are shown in the columns on the left.

For information about how to enter a recipe into the Recipe to Formula environment of Matrix click the help button on the right.

Click here for more information about Matrix's working environments.

The analysis of a raw material should be available from the retail supplier or the company which produces (mines or processes) that material. If a raw material is not already listed in a software's database then it's analysis should be obtained so that it may be entered into the software's databases.

There are various sources of raw material analyses on the internet. One of the most comprehensive may be found at: http://ceramic-materials.com/cermat/material/a.html

Manufactures often have websites with analyses of the raw materials they produce. An example of one of these is Pacerminerals.com This site lists the chemical analysis of the material Custer Feldspar. If this material was not already in the Matrix database then the analysis given by Pacer Corp. would enable the material to be placed into Matrix.

It is often easy to find a particular material analysis by using a search engine such as Google.

The diagram above "Graphical Representation of the Unity Formula for a Glaze" shows the balances of oxides in the fired glaze.

Many conclusions about the fired quality of a glaze may be drawn from this very simple theoretical structure. Of particular interest is the balance of flux to Al₂O₃ and to SiO₂. If the flux side of this balance always totals 1 (unity) then it is very easy to compare glazes in terms of the proportions of Al₂O₃ and SiO₂. Equally it is easy to relate these levels to tables (Limit Formulae) indicating the appropriate levels of Al₂O₃ and SiO₂ for certain firing ranges.

Matrix saves recipes into two different kinds of files depending on your needs. Individual recipe files contain information about one recipe only. These are very transportable and can be sent to others via email or on a CD where they may be stored in the appropriate Matrix folder then opened by booting Matrix and loading the recipe.

Matrix can also create a recipe database which is a collection of recipes. This format is useful for collecting recipes that have like qualities. The formulae for recipes saved in databases may be compared in tables or on graphs.

For information about how to save a recipe after entering it into the Recipe to Formula environment of Matrix click the help button on the right. Check also how to save a recipe to a database.

Click here for more information about entering a recipe into Matrix

A recipe that has been saved in Matrix may be retrieved (loaded) and displayed on screen with it's unity formula. The double recipe panel facility allows two recipes to be displayed at the same time for comparison - particularly when one of those recipes is being altered.

Click here for more information about retrieving a saved recipe in Matrix

	Activities

1. Enter some of your collection of recipes into Matrix and save them as individual files in the Individual Recipes folder.

Remember to set the temperature for each recipe you are entering before saving the recipe. You can organise the recipes you save by creating new folders inside your Individual Recipes folder.

Click here for more information about entering a recipe into Matrix

2. Compare a C.10 and a C.6 recipes in Matrix's Recipe to Formula envoronment.

1. Boot Matrix and expand the Recipe to Formula environment by clicking the button to display the second recipe panel.
2. Enter a C.10 recipe in the left hand panel and examine the left hand formula column which displays the unity formula as you enter the recipe.
   
3. Enter a second recipe in the right hand recipe panel this time for C.6. Examine again the unity formula for the recipe (in the right hand formula column) as it is the recipe is entered.

   Note: you will need to click the R.2 radio button to activate the second recipe panel before you can enter a recipe in that panel.

4. Examine the Al₂O₃ and SiO₂ unity formula levels for the two glazes and comment on their differences.
5. Make a general statement about the changes you would need to make to a glaze in order to make it melt to the same extent at a lower temperature

3. Enter and compare two C.10 Glazes

1. Enter the two C.10 glazes listed in the following chart below. Place one in the Recipe 1 panel and the second into the Recipe 2 panel in Matrix.
2. Study the two unity formulae generated by Matrix in the formulae panel.
3. Comment on the two recipes and the two formulae noting any similarities and differences. If there are any differences see if you can work out which materials generated those differences.

Work through GlazeTeach Unity 4 - The Unity Formula

Click this link to go to GlazeTeach Unit 4 - The Unity Formula

Note: the last topic - "Converting a unity formula to a recipe" will be covered later in this course.

Remember to keep records of your research and your glaze testing.

Make notes when working through the activities so that we can check your work for assessment.

If you have any questions . . . . .

Email. . . .lewing@woosh.co.nz

References

• Unity Formulae etc - http://www.ceramic-materials.com/cermat/education/189.html
• Pioneer Pottery by Michael Cardew has a brief overview of bring a formula to unity in Appendix II. This book is no longer in print, but is available in many libraries.
• Clay and Glazes for the Potter by Daniel Rhodes has been a standard pottery text for many years. Chapters 11 through 25 will be helpful; reading chapters 12, 13 and 14 will be most helpful.
• Potter's Dictionary of Materials and Techniques by Frank and Janet Hamer should be on every potter's shelf. Entries that are extremely useful for interpreting unity figures include: Fluxing action, Viscosity of molten glazes, Surface tension, Formula, Table of thermal expansion and contraction and Table of acceptable limits for unity formulae of glazes.