Potters & Sculptors - Making Rock from Mud
The molar percentages give you a better idea of how an addition will affect the glaze balance than weight percentages, because the molar proportions are directly related to the unity formula we use to evaluate what is a reasonable glaze composition chemically. It tells us the relative number of different component molecules in a material rather than the weights, and the molecular proportions are very different from the weight proportions. Here is an example of how different molar percentages are from weight percentages in the components of a ball clay.
You can download my Excel workbook here Materials Percentage Charts.xls. It is Excel Version 2003, and I believe it will work on Macs as well as PCs. You can copy any of the sheets and change the compositions to add your favorite materials that aren't on my list. You can also update the percentages of any of the materials as you find they change over time. The charts can help you visually decide which of alternative materials will work best to make the change you are after. To update the summary sheet, write in the name of the material in the left column. Go to the material page for that item and copy the range of oxide mole percentages from LiO to Total (even empty cells at the top). Back on the summary sheet select the cell just to the right of the material name you just typed in, and click the "paste special" item from the Edit drop down menu. In the dialog box that opens, check the "transpose" box to paste your mole percentages out horizontally rather than vertically. Click OK to complete the paste operation.
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