ForMatter/Finishes/glaze/Raku glaze (post-fire reduction)
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Raku glaze (post-fire reduction)

glaze · iridescent · raku-yaki, American raku, Western raku, post-fire reduction glaze
highlast updated 2026-04-28

A low-fire glaze pulled from the kiln red-hot and dropped into combustibles — sawdust, newspaper — that smother and reduce the surface. Copper turns metallic and rainbow; black slip carbonizes deep black; clear crackle glaze cools fast and crazes immediately. The signature finish of Western studio raku since Paul Soldner's 1960s adaptation of Japanese raku-yaki.

Glaze fired to ~1000 °C (cone 06), removed from the kiln glowing with tongs (uniformly thermal-shocked), dropped into a metal can with sawdust / newspaper / pine needles which ignites and is then sealed; oxygen-starved smoke reduces metallic-oxide colorants and carbonizes exposed clay. Copper-carbonate glazes go iridescent / metallic; clear / crackle glazes craze on the rapid cool, then trap smoke in the cracks for a black-line-on-white pattern. Body porosity high (low-fire), so raku ware is decorative — not for food / liquid hold. Modern American raku diverges from the Japanese tea-ceremony tradition (Raku-yaki, hand-built tea bowls, family lineage since 1574) which uses different clay and fires to lead-glaze chemistries.

character — iridescent metallic copper-and-bronze with black-crackle accents, soot-blacked clay, fast theatrical firing.

Finish properties

  • leveliridescent
  • subcategorylow-fire post-fire reduction
  • applies toceramic
Pairs with materials
Stoneware Clay
Terracotta (Low-Fired Earthenware Clay)

Second life

reversibilityzero — fired ceramic glaze cannot be unfired; the glassy layer is permanent. Damaged or chipped glaze can be re-glazed and re-fired with chemistry-compatibility planning.
blocks substrate recyclingno
renewabilitymoderate — re-glazing and re-firing is a studio-renewability path for damaged ceramic; the constraint is the original-firing temperature (the re-glaze must fire below the original).

Robin Hopper The Ceramic Spectrum (Krause, 2nd ed.); Daniel Rhodes Clay and Glazes for the Potter.

Citations