Casting organic materials (burnout)

Some natural materials (leaves, twigs, seeds, dried flowers) burn away completely inside a hot mold. They leave a cavity of their exact shape, which is filled with metal.

How it is done #

1. Choose a dry material that burns without much residue.
2. Attach a sprue with wax and mount it in the flask with investment.
3. The burnout kiln burns away the organic material and the wax, leaving the cavity.
4. The metal is cast as in lost wax.

Result #

A metal piece that reproduces even the veins of a leaf. Each piece is unique, because the model is destroyed.

Difficulties #

Ashes and gases can leave residue or pores; the model must be dry and clean.

Ethics #

Use responsibly collected materials and avoid protected species.

Step by step #

1. Choose the object. Leaves, twigs, dried flowers or husks.
2. Dry. Let it lose all moisture.
3. Attach a sprue. Fix it to a wax stem.
4. Invest. Cover with refractory plaster.
5. Burn out. The object burns away in the kiln.
6. Cast. Pour the metal into the cavity.

Tools and materials #

• Dried organic objects
• Refractory investment
• Burnout kiln
• Metal (crucible)

Common mistakes #

• Damp object: bubbles in the piece.
• Object too fine: it does not fill.
• Burning out insufficiently.
• Using protected species.

See also #

• Lost-wax casting
• Silver
• Centrifugal casting