PART 3 - "ROCKS IN THE HEAD!"
I STARTED TO REALIZE THAT A PIECE OF BISQUE-FIRED POTTERY IS ACTUALLY A CHUNK OF SIMULATED, POROUS ROCK. THE GLAZE THAT IS PUT OVER IT IS A COMBINATION OF OTHER ROCKS, POWDERED AND, WITH THE ADDITION OF WATER, MADE INTO A LIQUID. THIS LIQUID IS APPLIED TO THE BISQUE AND THE WATER EVAPORATES. ON FIRING TO A SUITABLE TEMPERATURE, IT TURNS INTO A SKIN OF GLASS AND FUSES TO THE CLAY, BECOMING FOREVER BONDED. THIS SAME PROCESS HAS BEEN UTILIZED BY MANKIND FOR 4,500 YEARS, ALMOST ALL OVER THE WORLD EXCEPT IN PERMAFROST OR HUMID JUNGLE CONDITIONS WHERE THE CLAY WILL NOT DRY ENOUGH TO BE FIRED WITHOUT EXPLODING FROM THE WATER CONTENT THAT TURNS TO STEAM WHEN HEATED. A ROCK IS GENERALLY A COMBINATION OF SEVERAL MINERALS. A CERAMIC MINERAL IS PURIFIED AND DECONTAMINATED. THE SELECTION OF THE DIFFERENT ROCKS AND MINERALS TO MAKE COLOR AND GLAZES IS A LENGTHY, CUMULATIVE, RESEARCH EXPERIENCE, LEARNING BY TESTING AND OBSERVATION. GLAZES WERE BEING MADE BY TRIAL AND ERROR FOR OVER FOUR THOUSAND YEARS BEFORE THERE WAS A CHEMICAL EQUATION BASED UNDERSTANDING AND GLAZES COULD BE CALCULATED PREDICTABLY. MY PREFERENCE IN GLAZE AND COLOR DEVELOPMENT IS BY EMPIRICAL MEANS OF LEARNING MATERIAL BEHAVIOR UNDER THE EFFECTS OF HEAT.
WHEN YOU LOOK AT CRYSTALS IN NATURE AS ABOVE, IT BECOMES EASY TO UNDERSTAND WHAT THEY DO IN GLAZES. RUTILE IS IMPURE TITANIUM, OR TITANIUM WITH IRON. THE MORE THAT YOU LOOK AT MINERALS, THE MORE YOU CAN VISUALIZE THEIR POTENTIAL IN GLAZES. MOST CERAMISTS BUY POWDERED AND PURIFIED COLORANTS. THE IMAGE BELOW SHOWS WHAT WE NORMALLY USE. THE IMAGES ABOVE SHOW A SMALL VARIETY OF WHERE THE POWDERED COLORANTS COME FROM.
ANY BASIC GLAZE IS A COMBINATION OF THREE THINGS, SILICA - WHICH FORMS GLASS AT AVERY HIGH TEMPERATURE; A SERIES OF FLUXING COMPOUNDS - THAT LOWER THE MELTING POINT OF SILICA, AS WELL AS CONTROLLING THE COLORATION POTENTIAL OF COLORANTS: AND ALUMINA - THAT ACTS AS THE BONDING MECHANISM BETWEEN THE GLAZE AND THE CLAY THAT IT COVERS. SOME OF THESE MATERIALS ARE ACIDIC AND AFFECT COLORANTS IN ONE WAY. SOME ARE ALKALINE AND AFFECT COLORANTS IN ANOTHER WAY. THE FINAL RESULT OF ANY GLAZE IS THE RESULT OF ANOTHER THREE THINGS. FIRST, THE COMBINATION OF MATERIALS THAT MAKE UP THE GLAZE. SECOND, THE TEMPERATURE AT WHICH IT IS FIRED. AND THIRD, THE ATMOSPHERIC CONDITIONS IN WHICH IT IS FIRED. TO THAT BASE, ONE ADDS COLORANTS AND OPACIFIERS TO ROUND OUT AND COMPLETE THE GLAZE AS DESIRED.
WHILE I REALIZE PERFECTLY WELL THAT NOT EVERONE HAS A MUSEUM OF GEOLOGY AND MINERALOGY ON THEIR DOORSTEP, THERE ARE MANY MINERAL AND ROCKHOUND STORES AND THE WILD AND WONDERFUL WORLD ORF NATURE. OBSERVE WHAT IS THERE AND IMAGINE HOW YOU COULD USE IT.