[Editor's note: print this document with a monospaced font (Monaco or Courier on a Macintosh) to have the graphs and tables appear in their proper format.] glz3b1.txt SWCC Clay and Glaze Formulation Robert Fromme OXIDE COMPARISON FOR MELTING TEMPERATURES, SURFACE TENSION AND EXPANSION\CONTRACTION ________________________________________________________________ This order is approximate. Conflicting rankings have resulted over the years from a variety of research. Where contradiction between sources can be found, they have been included to give a general idea of how data varies. The general categories of low, medium and high can still help the clay artist plan for glaze characteristics, trouble-shoot and correct problems. _________________________________________________________________ INCREASING RATE OF EXPANSION INCREASING SURFACE REFRACTORY AND CONTRACTION FROM TENSION TEMP. /\ VARIOUS TESTS /\ /\ || || || || Possible || Possible || Possible || Crazing || Crawling || Melting || Problems || Problems || Problems || || || || Na2O Na2O Na2O || Al2O3 (Alumina Oxide) || ZrO2 || K2O K2O K2O || MgO (Magnesium Oxide) || SrO2 || CaO CaO CaO || ZrO2 (Zirconium Diox.) || Al2O3 || BaO BaO || CaO (Calcium Oxide) || SiO2 || PbO BaO || SnO (Tin Oxide) || TiO2 || TiO2 ZnO PbO || ZnO (Zinc Oxide) || SnO2 || SrO PbO SrO || SrO (Strontium Oxide) || MgO || LiO TiO Li2O || BaO (Barium Oxide) || CaO || ZnO Al2O3 ZnO || SiO2 (Silicon Dioxide) || ZnO || MgO SrO MgO || TiO2 (Titanium Dioxide)|| BaO || ZrO2 LiO2 SnO2 || B2O3 (Boric Oxide) || B2O3 || SnO2 || Li2O (Lithium Oxide) || Li2O || Al2O3 SiO2 Al2O3 || PbO (Lead Oxide) || K2O || SiO2 MgO SiO2 || K20 (Potassium Oxide) || Na2O || B2O3 B2O3 B2O3 || Na20 (Sodium Oxide) || PbO || || || || Possible Dunting || Possible Dripping, || Possible || and Shivering || Running and excess || Boiling || Problems || Crystallization in || & Bubble || || the Cooling Kiln || Problems || || || \/ \/ \/ ----------------------------------------------------------------- Please note that the fluxing activity or melting information is based on assorted tests of single oxide elements and does not take into account the various eutectics which reduce melting points and stimulates chemical activity in the heated glaze mix. __________________________________________________________________ ------------------------------------------------------------------ (c) 1994 Robert Fromme For educational use, only.