Mastering the Art of Glazing Iron in Pottery and Ceramics

The Art of Glazing Iron

Glazing iron to achieve vibrant colors and textures has been a beloved pottery technique for generations. When done properly, iron glazes can transform plain clay into stunning works of art with deep, lustrous hues. As iron glazes mature over extended high heat firing, they develop their signature jewel-toned colors and mesmerizing drips and runs. Mastering the iron glaze requires an understanding of chemistry, patience through trial and error, and an artistic eye for beauty.

The Science Behind Iron Glazes

Iron glazes derive their intense colors from the dance of oxidation and reduction that occurs in the kiln. When clay pots coated with iron glaze are first placed in the kiln, the iron oxidizes in the heat and turns various shades of orange and brown. As the kiln temperature continues climbing, oxidation gives way to reduction, wherein there is less oxygen available. This causes the iron and other metals to break down and recombine as new vibrant compounds like spinach green copper, mustard yellow tin, and deep red-brown iron.

The glaze chemist balances various minerals, fluxes, and colorants to create the ideal environment for this transformation. Common ingredients include silica, borax, soda ash, dolomite, red iron oxide, and black copper oxide, though the possibilities for variation are endless. Controlling the kiln atmosphere during firing enables the artist to direct where drips flow and which colors emerge from the molten glass surface.

Achieving the Perfect Iron Glazed Finish

While glaze chemistry lays the foundation, the artist controls the final aesthetic through clay body selection, glaze application technique, and firing effects. Porous bodies like stoneware and earthenware provide the ideal canvas for iron glazes to spread, pool, and erupt. The clay body itself peeks through thin glaze layers, imparting flecks of brown and tan amidst the jewel tones. Brushing on glaze in irregular thick and thin layers encourages running rivulets and texture.

Raku and soda firing create signatures pitted peeling surfaces as carbon traps get burst open in the extreme heat. Alternately, reduction cooling in the kiln or smoking pots in a metal trash can draws out vivid glossy colors unachievable through oxidation alone. Sand, soda, salt, and other materials introduced during firing can leave delicious craggy textures and regional variations behind.

Designing With Iron Glazes

While high temperatures unlock the best colors, the relatively soft nature of iron glazes makes them ideal for low-temperature earthenware pots and tiles too. At cone 04-06 oxidized firings, iron mottles surfaces in rosy amber tones or applies slick and shiny like lipstick when over a colored slip. By imprinting fabric patterns and latex resist designs under runny iron at mid-range temps, the images emerge hauntingly diffuse through a veil of glass.

Vessels for Food and Drink

From mugs and goblets to serving platters, iron glazed pottery graces tables worldwide. As iron is toxic, such functional wares require a durable layer of transparent glaze over the iron to prevent leaching. Soda firing’s signature orange peel surface makes an exceptionally fitting backdrop for the jewel red peony glaze of Japanese raku tea bowls. The tradition of British ale drinking vessels sports blue pocked iron surfaces reminiscent of the night sky.

Sculptural Statement Pieces

Unencumbered by functional constraints, iron glazes liberally applied to sculpture and decorative ceramics display the best overall visual effects. Tree-like container forms encourage running drips that capture nature’s randomness beautifully. More abstract sculptures focus attention on the glaze surface itself as contours shape negative spaces around areas of dense pattern and color. The organic fluidity of iron glazing aligns effortlessly with ceramic’s plastic nature.

From traditional celadons to modern interpretations, iron glazed pottery always captures the imagination. Its depth, mystery and variability across firing methods position it securely among the great classic ceramic techniques.

FAQs

What clay bodies work best for iron glazes?

Porous earthenware and stoneware clay bodies provide the ideal surface for iron glazes to pool and run. The clay peaks through for an added depth and texture.

Do iron glazes require special firing methods?

Reduction firing, raku, and soda firing create signature looks impossible through oxidation alone. Controlling the kiln atmosphere is key to achieving vibrant colors.

Can I put iron glazes on functional pottery?

Yes, with an extra layer of durable transparent glaze over the iron to prevent leaching and toxicity.

What colors result from iron glazes?

Deep jewel tones like emerald green, sapphire blue, amethyst purple and ruby red. Natural clay tones also peek through for added depth and contrast.