PREAMBLE This programme and associated documentation were written by Dr. C. S. Hogg, B.Sc., Ph.D., F.Inst.Ceram., 17, St. Sulien, Luxulyan, Bodmin, Cornwall, PL30 5EB ENGLAND The programme and associated documentation are in the public domain for people to copy and distribute freely. The programme will run on most IBM PC machines or compatibles, under MS-DOS or DR-DOS. It may not run on machines without a colour monitor. There are three files: GLAZES4.EXE the programme. GLAZDAT2.DAT the data file. README.TXT these instructions. All three files should be included when making copies. Do not change the name of the data file. The programme is offered in good faith, but no responsibility or liability can be accepted by the author for any loss or damage arising from use of the programme. Use of the programme and the resulting recipes or compositions is entirely the responsibility of the user. INTRODUCTION This computer programme has been developed to overcome the problems met by the more technically minded studio potters in developing their own glaze recipes through the use of chemical analyses. Many potters are discouraged from doing calculations on glaze compositions by the complexity of the procedures or because they do not have the chemical analyses of their materials. Thus, much time is wasted on empirical experiments in attempts to produce satisfactory glazes. This programme will not give you instant success with your glaze trials; there is substitute for experiment! What it will do is allow you to calculate many types of glaze analyses quickly and accurately, thus eliminating many unsuitable recipes from the start. As well as interchanging glaze analyses between percentage and Seger formulae, the programme will allow you to compare the analysis of a glaze given in the form of a recipe with that given in the form of a percentage analysis or Seger formula. It will also allow you to calculate a glaze recipe to match a particular analysis, either of your own devising or because you want to use different materials to those specified in the recipe. The programme handles fifteen element oxides, including both ferrous and ferric iron, which permits calculation of glaze compositions under both oxidising and reducing conditions, with full correction of the Seger formula. This allows for the the fluxing effect of ferrous iron in reduction fired glazes. Potassium and sodium oxides can either be dealt with separately or combined together as the notional oxide KNaO. In addition, the oxide list can be amended to substitute the less common oxides of your own choice. All the calculations are done on the basis of the final analysis being that of a fired glaze, and the loss in weight of individual components on firing is automatically taken into account when calculating recipes or analyses. The programme contains a library of analyses for over 100 raw materials, including ball clays, frits, feldspathic minerals and a number of other natural raw materials. Facilities exist for amending any of these analyses to suit your own particular materials. Alternatively, analyses of unlisted materials can be included directly while calculating. The analyses of the library materials are usually those published by raw material suppliers. They refer to materials available in the U.K., but may not be appropriate for materials obtainable in other countries. Other analyses have been taken from reference books which quote typical data. A brief description of some of the materials may be helpful. The bentonite is from Redhill, Surrey. The Cement is typical of many Portland cements; glazes made with it should be used immediately, for obvious reasons. Only one china clay has been included because their analyses are all fairly similar, although some china clays may contain more titania and less potash. The Wood Ash is well-washed softwood ash from a domestic wood-burning stove. Volcanic ash, or pumice, is available from several potters' suppliers. Perlite is the white, lightweight insulating material available from D.I.Y. or garden centres. The Glass Cullet was at one time supplied by Wengers, but any ground up white bottle glass will be similar. The other frits are quoted by name, rather than by suppliers' codes, as these tend to vary from supplier to supplier. For those who want them, the Calcium Borate frit is Potterycrafts P2954; the Standard Borax frit was Podmores P2246; the High Alkali frit was P2250 also from Podmores, and the High Temperature Borax frit is Potterycrafts P2959. The Soft Borax frit was Wengers 1458W. The Sodium Silicate, M75, is included for those potters wishing to experiment with alkaline glazes low in alumina, such as turquoise copper glazes or zinc crystal glazes. It is a syrupy liquid but should be weighed out as per the computer recipe like any other material; add the other components to it, stir very well and paint onto a fully vitrified pot. Dry in a stream of warm air, using several applications if needed. Several of the materials have been collected from sources in Cornwall. They reflect my own interest in using local raw materials in glazes. As they are not available to most people, I suggest that the analyses are gradually over-written by analyses of your own materials, using the option to reset the library analyses (OPTION 5, see below), as and when appropriate. HOW TO USE THE PROGRAMME Throughout these instructions, means the or <Ù key. Selections from the main menu, and the Yes/No (Y/N) choices do not require the key to be pressed, but numerical values and Finish (F) commands do require pressing of the key. Upper or lower case are both acceptable. Typing an inappropriate letter will result in a beep. Load DOS (if this is not automatically done), then insert the programme disc, type GLAZES4 and press . After a short time during which the programme is loading into the computer and reading data, the MENU will be displayed. This offers ten options, as follows: 1 Conversion of a Seger (unity) formula to a percentage analysis. 2 Conversion of a percentage analysis to a Seger (unity) formula. 3 Calculation of a percentage analysis from a batch recipe. 4 Calculation of a batch recipe to match a percentage analysis. 5 The facility to review any of the library analyses. 6 The option to switch between K2O/Na2O and KNaO in calculations. 7 The option to alter the the list of oxides. 8 The facility to compare two analyses in the library. 9 The option to alter the weighting factors. 0 Finish with the programme. Select the option you require by its number, in response to the prompt. The use of the options will now be described in more detail. OPTIONS 1 AND 2: Interconversions between Percentage analyses and Seger formulae. Use of these two options is very similar. Depending on which you select, you will be asked to give the percentage or mole fraction of each oxide in turn. Press after each entry. It is not essential that the 'percentage' figures you give should actually total 100, as long as they are in the correct proportion, unless you are going to add the analysis to the library afterwards. In that case, the values MUST be percentages, although they may still not total 100 if the analysis includes a 'loss-on-ignition' figure, not called for in this programme (see later in this section). Similarly, the mole fractions do not have to conform to the Seger notation of fluxing oxides totalling unity, as long as they are in the correct ratio; for example, they could comprise mole percentages. When all the data has been entered, you will be asked whether the glaze is to be oxidised or reduced; reply O or R as required. The percentage analysis, by weight, and the Seger formula will be displayed in separate columns, together with the mole percentage analysis (the Seger formula expressed as a percentage). The molecular weight is given, calculated from the Seger formula. For most glaze calculations, this is quite straightforward, but calculating the molecular formula of a material that contains no alkalis presents a problem. Such formulae are usually normalised on another oxide, e.g. silica or alumina, but this is not always practical. In this programme, when no alkalis are present the formula is normalised on the first non-zero oxide in the list. The coefficient of thermal expansion is also calculated, as a percentage over the temperature range 0 to 500øC. This is done using the data given by W. G. Lawrence in "Ceramic Science for the Potter", p.144, published by the Chilton Book Co., Pennsylvania, with guesstimates to fill the gaps. The figure is less accurate for glazes containing much undissolved or recrystallised material such as opaque glazes, and for glazes high in lithia. The result can be used to indicate when crazing may be a problem, but as this is a function of the body as much as the glaze, it should only be used as a guide. At the bottom of the screen you will be asked if you want a printout of the display. Respond Y or N as appropriate. If Yes, you will be asked for a title. Type in the title and press , or just press if no title is required. The printer instructions are configured for dot-matrix printers with reverse paper feed facility. Other printers will work but the layout will not be as tidy. You will then be asked if you want to add this analysis to the library. This can be useful if you want to refer to it again in the future, either to compare it with another glaze analysis, or to construct a series of line blends between two end member glazes without typing in all the materials each time. All analyses are stored as oxidised percentages, regardless whether the analysis was originally typed in as a percentage or a Seger formula, or displayed in reduced form. If using OPTION 1, it will be assumed that the analysis is of a fired glaze, and the stored analysis will total 100. However, if using OPTION 2, the stored analysis will be exactly as fed in, and will not necessarily total 100. This is because the analysis could be of an unfired glaze, where the losses on firing are not included, but would have to be taken into account if constructing line blends between two such glazes. Give the number of a "SPARE" position or of a material whose data you wish to overwrite, and then the name you wish the analysis to be stored under. When you next list the library of materials, you will see the new name included. The next prompt will ask you if you want to work out a recipe to match the analysis you have just fed in. If you respond Y, the programme automatically moves into OPTION 4 (see below). The response N returns you to the main menu. OPTION 3: Calculation of a chemical analysis from a recipe. Selection of this option presents you with a list of components. Choose one by number, and press . Select the subsidiary lists for Ball Clays, Feldspars, Frits or Other Minerals. After each choice, you will be asked for the amount of the material you selected. This can be an absolute amount, as in a batch recipe, but if you are going to store the resulting glaze composition in the library, then it MUST be a percentage (see below). Press after each entry. You then have to choose the next component and its quantity, and so on, until you have fed in all the materials and their amounts in the recipe, when you should press F . The materials selected are displayed as they are chosen, with their proportions, so you don't have to remember where you've got to if you get distracted part way through. You are allowed a maximum of ten materials. If you want to use a material that is not in any of the lists and whose composition you know, you can select one of the "SPARE" options, when the computer will ask you for the name of the material and its percentage analysis. Press after each entry. Note that irrespective of whether you are in K2O/Na2O mode or KNaO mode (see OPTION 6, below), the computer will ask for K2O and Na2O as separate oxides, in order that it should have the most complete data available. If you only have the combined KNaO data, multiply this by 0.6 for the %K2O value, and 0.4 for the %Na2O value. Alternatively, use OPTION 2 in KNaO mode to type in the material analysis, and then transfer it to the library. If you have several such materials it may be better to use OPTION 5 (see below) to alter the library analyses before you start. These changes are retained in the memory until the programme is ended and can be retained permanently if required. After all the components and their proportions have been entered, and you have said whether the glaze is to be oxidised or reduced, the weight percent analysis, Seger formula and mole percent analysis will be displayed, as in OPTIONS 1 and 2, together with the recipe, also in percentages. You will also be asked if you want a printout; reply accordingly. You will then be asked if you want to add this analysis to the library. Note that if you do add the analysis to the library, the proportions of the raw materials you chose MUST have totalled 100, i.e. the proportions MUST have been percentages, not just the proportions in a batch recipe. If this is not done, the analysis stored in the library will not be correct, and cannot be used for subsequent calculations or comparisons. Give the number of a "SPARE" position, and then the name you wish the glaze to be stored as. When you next list the library of materials, you will see the new name included. Then you will be asked if you want to work out an alternative recipe, which will automatically take you into OPTION 4, below. Otherwise you are returned to the main menu. OPTION 4: Calculation of a Recipe from an Analysis. This option can be entered directly, or from OPTIONS 1, 2 or 3 above. If entered directly, you will have to give the target analysis, and confirm it. If the analysis does not total 100, perhaps because it is the analysis of an unfired glaze, the figures are recalculated to total 100. In all cases the target analysis is automatically oxidised. This simplifies the calculations, as all of the library analysis are in their oxidised forms. In addition, the calculations are made using percentages rather than molar proportions because the analyses are stored as percentages. You are then asked if you want a manual or an automatic calculation of the recipe. The manual calculation is interactive, in that the computer needs frequent instructions from the operator. The automatic calculation does all the hard work, and will probably give a better ultimate match between the target analysis and the calculated recipe. However it is not fast, sometimes taking over fifteen minutes. Reply M or A. 4a) Manual Calculation. In the manual calculation, the general approach is to select the raw materials you wish to use, in sequence, and subtract appropriate proportions of their analyses away from the target analysis, until there is nothing left. To begin with, the list of components is displayed as in OPTION 3 and the computer will ask you to select one by number. This is where you have to think a bit! Choose a particular material to provide a particular oxide or oxides: for example, choose whiting or wollastonite to provide calcia, a feldspar to provide alkalis, quartz to provide silica and so on. Press when you have made your selection. The computer will then show the analysis of the selected material alongside your target analysis, and ask you if you are still happy with your choice. Reply Y or N, after which you will be asked for the amount of that material. The best way to tell the computer the amount required, is to type in the ratio of the amount of the selected oxide in the target recipe to that in the chosen material. For example, if the target recipe contains 12.3% CaO, and you have chosen to use whiting to supply it, containing 56% CaO, then simply type in 12.3/56 exactly as I have typed it. The computer will work out the fraction, subtract off the appropriate amount of CaO, and remember how much whiting was needed. It is better to start with the materials that contain several oxides such as the feldspars, which contain silica and alumina as well as alkalis, and then finish with materials containing single oxides such as quartz, whiting or iron oxide. After a proportion of the first material selected has been subtracted from the target analysis, the computer will display three columns of figures. The first column contains the remainder after the previous subtraction (on the first time round, this is the same as the target analysis). The second column contains the proportion of the selected material being subtracted, and the third column contains the remainder after the second column has been subtracted from the first. Examine carefully the contents of the third column, to make sure you have not subtracted off too much of a particular oxide and produced a negative remainder. If all is satisfactory, choose another material containing another oxide and repeat the process. If you are not satisfied with any stage the computer allows you to go back and repeat that stage with a different proportion or with another material. The computer also allows you to Finish or Abandon at any stage (Type F or A). Finishing takes you to the end of the calculation and gives you the recipe and analysis so far achieved. Abandoning gives you the option of starting again or going back to the main menu. Assuming you proceed satisfactorily, successive remainders in the third column will get smaller and approach zero. There will come a point when the computer will ask if the difference between the target analysis and the new analysis is small enough for your satisfaction, i.e. whether the remainders are small enough. For the mathematically minded, this happens when the square root of the sum of the squares of the remainders gets below three. When using actual analyses of raw materials, rather than idealised or theoretical analyses, it is virtually impossible to get an exact match between analysis and recipe; you will almost always have to be content with a close approximation. If the match is close enough type Y, when the computer will display the original target analysis, the analysis of the new recipe, and a column of differences, plus or minus, between the two. At the bottom of this column is a figure called the "Residue", which is a measure of how close the two analyses agree. Again for the mathematicians, the "Residue" is the square root of the sum of the squares of the differences between the two analyses. Try to get the "Residue" to less than two, or better still to less than one. If you think the computer can improve on your match (and it usually can), you can ask it to fine-tune the recipe. Fine-tuning can take a little while, but may be less tedious than repeating the manual analysis several times to get it exactly right. Type R to get the recipe, and then Y if you want a printout. this will give both the recipe, the target analysis, the new analysis and the "Residue". You then have the option of having another go at producing a matching analysis, or returning to the main menu. This section sounds complicated, but is really very easy when you get the hang of it. Try a few simple exercises to start with. For example, enter OPTION 3 and calculate some simple analyses with Wollastonite and China Clay. Then move directly into OPTION 4 and try to match those analyses using Whiting, Alumina and Quartz. 4b) Automatic Calculation. If you choose this option, the computer asks if you wish to change the weighting factors. For more details on what these are, see the description in OPTION 8, below. When using the automatic calculation, choose at least two but no more than ten materials. Select each material in turn by number as in the other sections. When you have selected all you want, type F. The computer will then start it's calculation. This is iterative, which means it goes round and round, gradually getting a better match each time. On each cycle, it prints out the "Residue" and the proportions of each component in the order you chose them. Note that these proportions are usually less than one, but can be any value; the size is of no significance as it is just a relative figure. The actual calculation can take a little time, depending on the speed of your computer and the number of materials selected. If impatience gets the better of you, or you think the "Residue" is small enough, press any key and wait, and the calculation will end. When it has finished, the target and new analyses are displayed on the screen in the same way as with the manual analysis. You are then asked if you want another go, followed by whether you want a printout of the results. Reply accordingly. As already mentioned, the automatic calculation can also be used to fine-tune a manual calculation. This is often the best way to use it, unless you are fairly sure from the start that the materials you have chosen will give a reasonable match to your analysis. The programme will seldom give a recipe that is a perfect match to your target analysis, only the best match that can be achieved with the materials you have chosen. By way of rather extreme examples, it would be impossible to get a good recipe for a dolomitic glaze if no source of magnesium were provided. Similarly, a low-alumina high-alkali glaze will not be correctly matched if a feldspar is used as the only source of alkali, because the feldspar itself will probably introduce more alumina than is needed in the recipe. OPTION 5: Option to review the library analyses. If the analyses of any of your materials differ from those I have set up in the library, then you can use this facility to alter them. When you enter OPTION 5, you will see the list of raw materials as in OPTIONS 3 and 4. Select the material whose analysis you wish to review by number, as before. The computer will list the full analysis of that material for your inspection, and ask you if you still want to change it. Assuming you still do, you will then be asked whether you wish to change the name. Give the new name if appropriate, and then the percentage of each oxide in the analysis, in turn. Press after each entry. Note that irrespective of whether you are in K2O/Na2O mode or KNaO mode (see OPTION 6, below), when using OPTION 5 the computer will display and ask for K2O and Na2O as separate oxides, in order that it should have the fullest data available. If you only have the combined KNaO data, multiply this by 0.6 for the %K2O value, and 0.4 for the %Na2O value. Alternatively, use OPTION 2 in KNaO mode to type in the material analysis, and then transfer it to the library for later use. If you wish to remove an analysis from the library without replacing it by that of another material, call the material SPARE, and replace all the analyses with zeros. During subsequent calculations, the computer recognises the name SPARE as being that of a vacant slot. These additions or changes to the library are only retained as long as the programme is running. When the programme is reloaded, the old analyses will be restored unless you have saved the new ones in OPTION 0, see below. OPTION 6: Option to change from K2O/Na2O to KNaO. Selection of this option allows switching between K2O and Na2O as separate oxides, or using the KNaO combination. Many potters prefer to do their glaze calculations with the K2O and Na2O combined together into a notional oxide, KNaO. It is argued that K2O and Na2O are more or less interchangeable in a glaze composition, and as a result it doesn't make a great deal of difference to the quality of the glaze whether the calculation is done with the two oxides separate or combined. Calculations of recipes to match analyses are much easier using the combined oxides. There are certain inevitable differences between working with the oxides separately or in combination. Calculation of a Seger formula from a percentage analysis gives a slightly different result due to the use of an average formula weight for the combined oxide. Only in the uncommon events of the ratio of %K2O to %Na2O being 1.5:1 or the molar ratio being 1:1 will the Seger formula remain unchanged. In the KNaO mode, when an analysis is typed in via OPTIONS 1 or 2 and added to the library, the computer is unable to separate the two oxides correctly if you then change to the separate oxide mode, as it has no information to go on. In these circumstances, in OPTION 1, the Seger formula, the computer divides the KNaO value equally between K2O and Na2O. In OPTION 2 using percent analyses, the computer divides the combined KNaO percentage oxide sum in the ratio 1.5 parts K2O to 1 part Na2O, the ratio of their formula weights. Thus, in the Seger formula 0.3 KNaO becomes 0.15 K2O and 0.15 Na2O, and in the percent analyses, 10% KNaO becomes 6% K2O and 4% Na2O. When OPTION 5 is selected, analyses are displayed and modified in separate K2O and Na2O mode regardless of the mode selected from the main menu. See under that heading for more details. The library of raw materials is always saved in the separate K2O and Na2O mode, regardless of the mode you are in when you finish the programme in OPTION 0, see below. OPTION 7: Changing the list of oxides. Although the existing oxide list is fairly comprehensive, it is possible that at times you will want to use oxides that I have not included. The computer will list the oxides by number and will ask you which one you wish to change. Type 0 if no change is required or when you have finished. Then it will ask for the oxide formula and its formula weight. Give these two in sequence, separated by a comma. Some examples of possible oxides and their formula weights are given. Try to replace fluxing oxides by fluxing oxides, acidic oxides by acidic oxides, and so on, so that the Seger formula is correctly calculated. The computer will not allow you to change Fe2O3 or FeO, as these oxides are linked in the reduction/oxidation calculation, nor will it allow you to change K2O, Na2O or KNaO, as these oxides are linked in the alkali option. Their replacement could result in nonsensical calculations. Note that the replacement oxides will not always appear in the print-out headings, and you may have to resort to a pen to alter them. The figures themselves will be correct, however. Changes to the oxide list only last for as long as the programme is running. When the programme is reloaded, the original oxide list is restored. OPTION 8: Comparing two library analyses. This option is useful if you want to compare the analyses of two materials previously stored in the library, for example, two glazes of similar but slightly different compositions calculated earlier in OPTIONS 1, 2 or 3. Select the two materials whose analyses you wish to compare, in turn. The computer will then ask whether you wish to compare the analyses as weight percentage analyses or as Seger formulae; reply W or S as appropriate. If you chose the Seger option, you will be asked if you want to compare the analyses in oxidised or reduced form; reply O or R as appropriate. This last choice is not offered if you are comparing percentage analyses, as in this case the numerical differences between oxidised and reduced forms are small. OPTION 9: Changing the weighting factors. When the computer is doing an automatic recipe calculation, it normally gives equal weighting to the differences between the target and calculated recipes for all the oxides . This usually means that oxides present in large amounts such as SiO2 or Al2O3 will dominate the calculation, and will be the best matched. While this is quite satisfactory in most cases, there may be occasions when it is important that a good match is achieved between certain minor oxides, for example iron and titanium oxides in reduction fired celadon glazes. In this case, the weighting factors for those oxides can be increased, or alternatively they can be decreased for the other oxides, as required. This forces the computer to achieve a better match between the target and new recipes for these particular oxides, possibly at the expense of a poorer match for other oxides. The factors change up or down in multiples of ten, as smaller changes have no great effect. Changes to the weighting factors only last for as long as the programme is running. When the programme is reloaded, the weighting factors are all set equal again. OPTION 0: Finishing with the programme. When you have finished with the programme, select this option. It is unwise to 'crash out' of the programme by just switching off the computer, as data may be lost or corrupted. If you have made any changes to the library analyses, the computer will ask you if you want to save those changes so that they are available next time. If you have added a new raw material to the library, you will probably want to use it again in the future. On the other hand, if you have been using the library as a scratch pad and storing some analyses on a temporary basis for comparison, you may not want to keep them. Reply Y or N as appropriate. The library is always saved with K2O and Na2O stored separately, regardless of which mode you were in when you finished the programme. The data is stored as a CSV file, with the material name followed by the fifteen oxide percentages and then the next name and so on. The file can be read by a word processor and edited separately if required, but this is not recommended for the novice.