When Glaze Runs: Damage Control
Even experienced potters occasionally have a glaze run: a pot where the glaze flowed down and stuck to the kiln shelf, or pooled around the base of another pot. Knowing how to deal with the aftermath saves both the pot and the shelf.
Glaze Stuck to the Shelf
If a pot has fused to the shelf with hardened glaze:
- Do not force it. Trying to lever a pot off a shelf by hand will crack the shelf or the pot.
- Use a chisel and hammer to carefully chip the glaze crust around the base of the pot. Work in small taps around the perimeter, not one heavy blow.
- Once the pot is free, grind the remaining glaze off the shelf with a rubbing brick. The kiln wash under the run should have protected the shelf itself.
Grinding the Foot Ring
After a run, the bottom of the pot will have sharp, hardened glaze residue. Use a diamond grinding pad or a bench grinder to smooth the foot ring so it does not scratch surfaces. Always grind in a wet environment or wear a dust mask; glaze dust contains silica and flux materials that are harmful to inhale.
Preventing Runs in the First Place
- Wipe the bottom 1 cm of every pot clean of glaze before loading.
- Keep glaze thickness consistent; thick glaze flows more.
- Test new glazes on small test tiles before using them on finished pieces.
- Never trust a new glaze on a treasured piece the first time you fire it.
Run-Risk Triage
When loading:
- Place known runners on higher shelves over catch tiles
- Give risky pieces extra foot clearance
- Keep a mental note of which combos need thicker wash under them
This way, occasional experiments do not take whole shelves with them.
The maintenance work is unglamorous, but it keeps your studio running and your work coming out cleanly. Every skilled potter knows their grinding brick as well as they know their favourite tool.
Keep Exploring
Preventing glaze runs is closely tied to understanding glaze defects and how different glaze chemistries behave at temperature. The discipline of testing new glazes on small tiles before committing them to finished work is a hallmark of studio pottery practice worldwide.
Common Mistakes and Quick Fixes
- Trying to pry fused pots off by force: Chip carefully in stages instead.
- Not smoothing run scars on feet: Grind feet clean so finished pieces are usable.
- No risk strategy for known runners: Place risky ware over catch tiles and safer zones.
- Skipping post-mortem after a run: Record glaze combo and thickness to prevent repeats.
Practice Exercise
Build a “run-risk” list of your top five glazes, with notes on overlap behavior and safe placement zones in your kiln. Update after each firing. This converts accidental runs into controlled experimentation.
