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Dolomite is a key material for glazes, especially mattes. We were forced to adopt a new brand and needed confidence it was equivalent. Three tests were done to compare the old long-time-use material (IMASCO Sirdar) with a new one (LHoist Dolowhite). The first melt flow tester compares them in a very high dolomite cone 6 recipe formulated for this purpose; the new material runs just slightly more. The second tester is uses the G2934 cone 6 MgO matte recipe with 5% black stain; the new material runs a little less here. The third test is the high dolomite glaze on a dark burning clay to see the translucency and compare the surface character. They are very close. These three gave us the confidence to proceed.
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This is a 3D rendering of our melt fluidity tester. We have promoted this device for many years as an effective way to compare fired glaze properties (e.g. melt fluidity, surface tension, bubble retention, crystal growth, transparency, melting range, etc). Open the 3MF file in your slicer, move all pieces off the print bed and unselect them all. Then, print each part by moving it onto the bed and using place-on-face to orient it right. Print the funnel wide-side down with brim. Insert the natch clips and embeds into the holes, pour in the plaster, let it set and finally remove the PLA with a heat gun. You now have a working mold to make slip cast testers. Glue the natches and spacers into the embeds, strap the mold together, glue in the pour spout with slip and finish by filling the mold with slip. If the mold is dry, 10-15 minutes should be enough to get adequate thickness (don't make them too heavy). With 0.8mm thick walls, this drawing 3D prints quickly and is easy to remove when the plaster has set (using a heat gun). The halves interlock using natches (requiring our embeds and related parts). The mold halves can also be lined up by the outer edges before clamping them together (thus not requiring natches).
Glossary |
Material Substitution
Material substitutions in ceramic glaze and body recipes must consider their chemistry, mineralogy and physical properties |
Glossary |
Melt Fluidity
Ceramic glazes melt and flow according to their chemistry, particle size and mineralogy. Observing and measuring the nature and amount of flow is important in understanding them. |
Materials |
Dolomite
An inexpensive source of MgO and CaO for ceramic glazes, also a highly refractory material when fired in the absence of reactant fluxes. |
Tests |
Glaze Melt Flow - Runway Test
A method of comparing the melt fluidity of two ceramic materials or glazes by racing them down an inclined runway. |
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