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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). The following list of concepts are discussed in detail in the Lesson Notes below.
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.)
Equipment and Materials Required
Please study the following notes and supplement the information with readings from your books, magazines and internet resources.
Feel free to email lawrenceewing8@gmail.com 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.
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.
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.
1. Enter some of your collection of recipes into Matrix and save them as individual files in the Individual Recipes folder.
2. Compare a C.10 and a C.6 recipes in Matrix's Recipe to Formula envoronment.
3. Enter and compare two C.10 Glazes
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. . . .lawrenceewing8@gmail.com References
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Contact: Lawrence Ewing - 1015 Ellis Rd, Five Rivers, RD3, Lumsden, Northern Southland,
New Zealand |