Kiln Shelf

What it is

A kiln shelf is a flat slab of refractory material — cordierite, mullite or silicon carbide — that carries the work and defines each level of a stacked load. Posting shelves on ceramic props lets a kiln be filled in layers, so the usable volume is several times the chamber floor.

Shelf material determines behaviour. Cordierite is inexpensive and handles thermal shock well but sags at high temperature under load. Mullite and high-alumina shelves are stiffer and better for cone 10. Silicon carbide is the most durable and the most expensive, and it resists glaze drips better than the others.

The single habit that preserves shelves is coating them with kiln wash — a refractory slip that stops a running glaze from fusing to the shelf. A drip on bare shelf material will bond permanently; the same drip on kiln wash lifts off after firing. Re-coat shelves whenever the wash wears thin or glaze has stuck.

How to use it well

• Coat every shelf with kiln wash and re-coat before it wears through.
• Use three or four posts per shelf, placed directly above the posts below, to build a stable column.
• Keep a 2 cm gap between the load and the kiln wall for even heat.
• Store shelves on edge in a rack; stacking them flat invites warping and chipping.
• Mark the underside of each shelf so you always load it the same way up.

Safety notes

• Kiln wash contains alumina and kaolin dust — mix and apply wearing a respirator.
• Never handle a shelf without gloves during or after firing; shelves hold heat for hours.
• A cracked shelf can fail under a heavy load. Retire it rather than risk a collapse.

Compatible materials

Clay bodies

• All bodies

Glazes & surface

• Protects against all running glazes

Where it sits in the process

Bisque, glaze and specialty firings in the kiln.

Firing  Kiln & Firing  Entry tier

Browse every tool in this stage from the Kiln & Firing category.