A Glaze Kiln Is Not a Bisque Kiln
After bisque firing, your pots have no glaze on them and nothing sticks to anything. Loading a bisque kiln is relatively forgiving: you can stack pieces inside each other and pack the shelves tightly. A glaze kiln is completely different. Glaze melts. Any piece touching another piece, or touching a kiln shelf without a barrier, will fuse permanently.
The Golden Rule: Nothing Touches
Every glazed surface must have clearance from every other surface and from the kiln shelf. This applies to:
- Pot-to-pot: Two glazed pots must never touch. Even a 2-3 mm gap is enough.
- Pot-to-shelf: The base of every pot must be free of glaze. If glaze runs to the foot, it will bond to the shelf.
- Glaze on the bottom: Always wipe, scrape, or wax the bottom centimetre of every pot before loading. This is non-negotiable.
Glaze-Load Precheck
Before you start loading:
- Visually confirm every foot is clean and/or waxed
- Group pieces by height to plan shelf spacing
- Set aside any “drippy” glazes for top or sacrificial shelves
A few minutes of planning prevents hours of grinding later.
Kiln Wash
Kiln wash is a refractory coating brushed onto kiln shelves before every glaze firing. It creates a sacrificial layer that glaze will not bond to permanently; if a glaze drip reaches the shelf, you can chip it off the kiln wash rather than destroying the shelf.
Apply kiln wash in thin, even coats with a wide brush. Let it dry fully before loading. Never apply kiln wash to the underside of shelves or to the kiln walls.
Go Deeper
Kiln shelves and posts are made from refractory materials designed to withstand repeated high-temperature firings without warping or cracking. The importance of proper kiln loading becomes especially clear when working with glazes that approach vitrification temperatures, where even small errors in clearance can fuse pieces permanently.
Common Mistakes and Quick Fixes
- Bisque loading habits in glaze firing: Never stack glazed ware or let surfaces touch.
- Skipping bottom checks: Build a foot-clean check into loading flow.
- Treating kiln wash as optional: Refresh shelves regularly to protect expensive furniture.
- Packing too tightly near drippy glazes: Give high-flow pieces extra space and safer placement.
Practice Exercise
Before your next glaze load, stage all ware on a table and do a dry-run shelf map by height and run risk. This planning exercise usually increases capacity and reduces breakage in the same firing.
