MATERIAL GUY - PART FIVE: IRON

MONDAY, 6TH MARCH 2012

THE CERAMIC SPECTRUM

TODAY'S POST COMES TO YOU 

COURTESY OF THE MINERAL :  IRON

I CAME TO ALL OF THIS GLAZE AND COLOR RESEARCH STUFF AS A RESULT OF PURE FRUSTRATION. 

I WAS INITIALLY TRAINED AT ART SCHOOL IN PAINTING, DRAWING

AND PRINTMAKING. THERE ONE BOUGHT TUBES OR JARS OF PAINT WITH DESCRIPTIVE NAMES ATTACHED. YOU KNEW WHAT YOU WERE GETTING. THIS WAS IN THE 1950'S. IN CERAMICS, IT SEEMED THAT THERE WERE ONLY THREE GLAZES AVAILABLE, CELADON (GREEN), TENMOKU (BROWN) AND HIGH ALUMINA MATT (SPOTTY WHITE), AND ALMOST EVERYONE WAS USING THEM. I KNEW FROM MY MUSEUM VISITS THAT THERE WAS SO MUCH MORE THAN THAT. 

 I WANTED TO WORK THE CERAMIC SURFACE AS A PAINTER WORKS CANVAS. AT THE TIME THERE WERE FEW CERAMIC REFERENCE BOOKS ON COLOR AND WHAT LITTLE THERE WAS WAS VERY GENERALIZED TO THE POINT OF BEING ALMOST USELESS. IRON, IT WAS SAID, GAVE YOU BROWN OR GREEN. COPPER WOULD GIVE YOU RED OR GREEN.  SO THEY DO, BUT THAT IS ONLY A FRACTION OF WHAT THEY WILL GIVE YOU. I SET ABOUT FINDING OUT FOR MYSELF WHAT ANYTHING WILL DO AND WHAT ARE THE PRIMARY FACTORS IN GLAZE AND COLOR DEVELOPMENT. IT TOOK ABOUT 20 YEARS TO FIND WHAT I FELT I NEEDED TO KNOW. I WAS ASKED TO MAKE IT  INTO A BOOK FOR THE BENEFIT OF OTHERS WHO MIGHT BE PRE-OCCUPIED  WITH CERAMIC GLAZE AND COLOR DEVELOPMENT.

"THE CERAMIC SPECTRUM" IS DESIGNED LIKE A CERAMIC COURSE OUTLINE AND HAS SEVERAL HUNDRED BASE GLAZE RECIPES FOR DIFFERENT TEMPERATURES. CHAPTER 18 IS A LISTING OF WHAT YOU MIGHT NEED TO GIVE A SIMILAR RANGE OF COLOR TO WHAT YOU WOULD FIND ON A PAINT SAMPLE SHEET FROM AN ART SUPPLY STORE.

BASICALLY, WHAT ANY COLORANT WILL GIVE YOU DEPENDS ON THREE VARIABLES: 

1.    THE MATERIALS THAT MAKE UP THE BASE      GLAZE,   PARTICULARLY THE FLUXES;

2.        THE TEMPERATURE AT WHCH IT IS FIRED;

3.  THE CONDITIONS IN WHICH IT IS FIRED, BASICALLY OXIDATION OR REDUCTION.

YOU CAN ADD TO THAT ANY OPACIFIERS (USUALLY WHITENERS, PASTEL FORMERS OR TINTS) OR DARKENERS (TONES) AND THE DEGREE OF SATURATION IN RELATION TO THE GLAZE.

"MAGICOLORMAN"

A VERY SMALL, RANDOM  SAMPLE OF THE COLORS THAT COME FROM

 IRON IN A VARIETY OF GLAZES, FIRED AT DIFFERENT TEMPERATURES IN BOTH OXIDATION AND REDUCTION

IRON IS THE MOST COMMON AS  WELL AS THE MOST USEFUL OF THE COLORING OXIDES. ALMOST ALL CLAYS AND MANY GLAZE MATERIALS CONTAIN TRACES OF IRON THAT AFFECT COLOR, EVEN WHEN  IRON IS NOT ADDED TO DEVELOP A SPECIFIC COLOR. IRON IS THE MOST COMPLEX OF OXIDES IN ITS EFFECT ON BOTH BODY AND GLAZE COLOR. IN OXIDATION, IT PRODUCES YELLOW, ORANGE, RED, BROWN, PURPLE AND BLACK. IN REDUCTION, IT CAN PRODUCE BLUE, GREEN, GREY, YELLOW, PURPLE, PINK, ORANGE AND BLACK. IN BOTH OXIDATION AND REDUCTION, COLOR WILL BE DEPENDENT ON THE THREE VARIABLES. IN CONJUNCTION WITH IMPREGNATED CARBON, IT WILL CAUSE THE DEVELOPMENT OF A BLACK BODY IN EITHER PIT-FIRING,  OR THE POST-FIRING REDUCTION OF RAKU.  IN HIGH-FIRED STONEWARES AND IMPURE PORCELAINS, RED TO PINK TO BROWN COLORS CAN DEVELOP AS FLASHING DURING THE RE-OXIDATION OF REDUCED WARE DURING COOLING. IRON CAN ALSO PRODUCE A GREAT VARIETY OF MICRO CRYSTALLINE SURFACE COLOR AND IN-GLAZE SPARKLING CRYSTALS SUCH AS AVENTURINE GLAZES. IN OXIDATION, IRON REACTS AS A REFRACTORY, RAISING THE TEMPERATURE SLIGHTLY. IN REDUCTION, IT REACTS AS A FLUX, LOWERING THE TEMPERATURE SLOWLY.

IRON COMES IN MANY FORMS BUT IN THE FIRING THEY ALL TURN INTO OXIDES. ONE BENEVOLENT ASPECT IN USING YELLOW IRON OXIDE, AS OPPOSED TO RED IRON OXIDE IS THAT IT DOESN'T STAIN HANDS AND CLOTHES AND JUST ABOUT EVERYTHING ELSE, BUT GENERALLY BEHAVES JUST LIKE RED IRON IN THE FIRED CERAMIC FORM.

MUCH FURTHER INFORMATION ON IRON CAN BE FOUND IN  CERAMIC SPECTRUM, CHAPTER 15, ON IRON COLORED GLAZES, SHINO GLAZES, CHUN AND CELADONS.

THE NEXT POST WILL PRIMARILY DEAL WITH THE EFFECTS OF COPPER IN GLAZES.

ALL BEING WELL, IT WILL APPEAR ON WEDNESDAY, 7TH MARCH, 2012.