To Techniques

Copper fuming is a raku variant in which copper compounds are introduced into the reduction chamber during the smoking stage, producing metallic, iridescent surfaces in blues, pinks, golds, and greens rather than the classic black-and-white crackle of standard raku. The copper vaporises in the heat and settles back onto the pot's surface as a thin, lustrous film — closer to the sheen on a soap bubble than a painted colour.

Where Copper Fuming Comes From

Copper fuming grew directly out of the Western raku tradition established by Paul Soldner and other American potters from the 1960s onward, as ceramicists experimented with introducing different materials into the post-firing reduction stage. Where standard raku relies on carbon from smoke settling into the crackled glaze, copper fuming works differently — copper carbonate or copper matte glazes are heated to the point of vaporising, and that copper vapour deposits a thin metallic film directly onto the piece's surface inside the closed reduction container.

It's become one of the most visually striking raku variants precisely because the results are so unlike anything else in ceramics — genuinely metallic, shifting in colour depending on the angle of light, closer to the surface of an oil slick or a beetle's wing than to a fired glaze.

How the Process Works

1. Bisque fire first — as with all raku work, pieces must already be bisque-fired.

2. Apply a copper-rich surface — either a copper matte glaze, or bare burnished clay with copper carbonate to be introduced during reduction.

3. Fire fast and hot — the kiln is brought up to raku temperature, typically 950–1000°C, until glazed surfaces are glossy and molten.

4. Pull it red-hot — the piece comes out of the kiln glowing, using long tongs.

5. Fume it — the hot piece goes into a reduction container along with combustible material and additional copper carbonate or copper wire, which vaporises in the heat.

6. Seal, reduce, and clean — the lid goes on, starving the chamber of oxygen so vaporised copper settles onto the surface; once cooled, the piece is gently cleaned to reveal the metallic fuming beneath any soot.

What Creates the Colour and Marking

• Copper carbonate or copper matte glaze — the source material for the fuming

• Reduction intensity — how starved of oxygen the chamber becomes affects the depth and shift of colour

• Cooling speed — slower cooling within the chamber can shift tones toward pinks and golds; faster reduction often favours blues and greens

• Surface preparation — burnished or terra sigillata surfaces take the metallic film more evenly than rough bisque

Is Copper-Fumed Pottery Food Safe?

No. Like all raku work, copper-fumed pieces are non-food-safe and porous. The rapid firing and reduction process, combined with the copper surface itself, make these strictly decorative pieces — vases, sculptural forms, wall pieces — never intended for food or drink contact.

What You Need to Try It

• Bisque-fired stoneware with a copper matte glaze, or a burnished/terra sigillata surface for bare-clay fuming

• Copper carbonate or copper wire for the reduction stage

• A raku kiln capable of a fast, hot firing

• A sealed reduction container, combustible material, tongs, and heat-resistant gloves

• Good ventilation — copper fuming produces more noticeable fumes than standard raku, so outdoor or well-ventilated firing is essential

This is not a beginner-friendly technique to attempt solo without guidance — the fuming stage in particular benefits enormously from hands-on instruction the first several times.

Try It Yourself

I run raku copper fuming workshops at my studio in Koringberg, in the Swartland, about an hour from Cape Town — often paired with obvara firing across a single workshop day. No experience is necessary; I provide the kiln, copper materials, and guidance through the fuming process.

See Copper Fuming Workshops

Frequently Asked Questions

Can beginners do copper fuming?

Yes, with guidance. The firing and reduction stages need close supervision the first few times, but no prior raku experience is required.

How is copper fuming different from standard raku?

Standard raku relies on carbon smoke settling into crackled glaze for its black-and-white effect. Copper fuming introduces vaporised copper into the reduction stage instead, producing a metallic, iridescent surface film rather than a crackle pattern.

Why do the colours vary so much between pieces?

Reduction intensity, cooling speed, and surface preparation all influence the final result, and small variations in any of these produce noticeably different colour outcomes — this unpredictability is part of what makes each piece unique.

Is copper fuming safe?

It requires the same fire safety precautions as standard raku, plus good ventilation, since vaporising copper produces fumes that shouldn't be inhaled in an enclosed space.

How long does a copper fuming firing take?

Similar to standard raku — a single piece can go from kiln to finished result in under an hour, though a full workshop day typically includes multiple firings and preparation time.