Kiln Shelves, Posts & Kiln Wash: Complete Setup Guide

Kiln Shelves, Posts, and Kiln Wash: Everything You Need to Know

Your kiln is only as good as how you load it. Even a perfectly tuned kiln will give you uneven, frustrating results if your shelves are warped, your posts are mismatched, or your kiln wash is flaking onto your glazed pieces. This guide covers everything you need to know about kiln furniture and how to set up a proper kiln load.

What Is Kiln Furniture?

Kiln furniture is the collective term for the refractory shelves, posts, and other supports used to stack pottery inside the kiln during firing. Without kiln furniture, you could only fire one layer of pottery on the kiln floor. With proper shelf and post setups, you can stack multiple layers and dramatically increase how much you fire per load.

Kiln Shelves: Types and Sizes

Kiln shelves come in several materials. The most common are:

Cordierite shelves: The standard choice for most electric kiln potters. Cordierite handles thermal shock well, is relatively affordable, and is widely available in round and rectangular shapes to fit different kiln interiors.

Advancer (nitride-bonded silicon carbide) shelves: Thinner, lighter, and more durable than cordierite. They conduct heat better, which means more even firings. Significantly more expensive — but many serious production potters consider them worth the investment because they warp less over time and require less kiln wash.

Shelf size matters too. Use shelves that leave at least a half-inch gap between the shelf edge and the kiln wall on all sides. This allows heat to circulate evenly around the load.

Kiln Posts: How to Stack Properly

Posts support the shelves and create the vertical spacing between layers. They come in a range of heights — typically from 1" to 12" — so you can customize shelf spacing to fit your tallest pieces.

The key rule: always use three posts per shelf, not four. Three points of contact are inherently stable on any surface, even if the shelf is slightly warped. Four posts create a rocking platform that stresses the shelf and causes uneven weight distribution.

Place posts directly above the posts on the shelf below — stacking forces should travel straight down through the kiln. Never cantilevered or offset.

Kiln Wash: The Essential Shelf Protector

Kiln wash is a refractory coating applied to the top surface of kiln shelves to prevent melting glaze from bonding permanently to the shelf. Without it, a single glaze drip can ruin a shelf.

The standard mix is roughly 50% alumina hydrate and 50% EPK kaolin, mixed with water to a thin cream consistency. Apply with a wide, soft brush in even strokes — you want full coverage but not a thick, lumpy coat.

Apply kiln wash only to the top surface of shelves, never the bottom. Kiln wash on the bottom of shelves can flake off and fall onto pieces below, ruining your work.

Reapply a fresh coat before every glaze firing. When build-up becomes thick and starts to crack or flake, grind or scrape the shelf down and start fresh.

What Not to Do

Never glaze the bottom of a pot and fire it directly on a shelf — the glaze will melt and permanently bond the piece to the shelf. Always leave the bottom half-inch of any glazed piece completely glaze-free, or use a wax resist on the foot ring.

Never overload your kiln. Leave airspace between pieces for heat circulation. Pieces touching each other can fuse together in a glaze firing.