Glazing a teapot is not the same job as glazing a bowl. A bowl only has to look good and hold soup. A teapot has to do several things at once: the lid must lift off, the spout must pour, the body must survive sudden heat, and the inside must sit with hot water for years without giving anything back to the tea. Each of those requirements opens its own door to a glaze fault. The good news is that nearly all of them are predictable, and most are decided long before the kiln lid comes down.
Pinholes: Gas That Never Got Out
A pinhole is a small crater in the fired glaze, sometimes with an open pore at the bottom. On the outside of a pot you might shrug it off as character. Inside a teapot it becomes a pocket that holds tea and stains, and if the glaze there is thin, it is also a weak spot in the liner.
Pinholes come from gas escaping through a glaze that has already sealed over. The usual sources are a bisque firing that went too fast and left carbon in the clay, dust sitting on the bisque surface, glaze applied so thickly that it skins before the body stops bubbling, and glaze materials that decompose late in the firing.
- Fire bisque slowly and hold at the end of the cycle so carbon has time to burn out.
- Rinse or damp-sponge the bisque and let it dry completely before glazing. This removes dust and gives the glaze something to grip.
- Keep coats thin. Three thin layers heal better than one heavy one.
- Add a short soak at the top of the glaze firing so bubbles can rise and the surface can level.
Crawling: When the Glaze Pulls Back
Crawling looks like the glaze retreated into islands, leaving bare clay channels between them. It is a bonding failure, and it almost always starts before the kiln. Dust or oil on the bisque, a fingerprint on the shoulder, a glaze mixed too thick, a recipe with so much clay that it shrinks hard before it melts, or a firing that climbs too fast through the early stages while the glaze is still fragile.
Handle bisque as if it is about to be photographed. Every fingerprint you leave is a spot where the glaze may refuse to stick.
Wear clean gloves or handle only the foot ring. Wipe the whole pot with a damp sponge and let it dry before dipping. Sieve your glaze rather than trusting the bucket. Build thickness in layers with drying time between them, and slow the first part of the firing so the glaze can melt and grab the clay before anything else happens to it.
Drips, Runs and Pools
Teapots are full of places where glaze collects: under the spout, around the handle roots, along the belly of a round body, and in the gallery where the lid sits. A run that reaches the kiln shelf becomes a chipping job with a chisel, and a drip that sets on the spout makes the pot look tired before it has poured a single cup.
Practical control
- Keep the glaze at a consistent thickness and time your dips. A bucket that gets watered down over a session will give you thin pots by evening.
- Use wax resist under the spout, at the handle roots, and on the foot.
- Wipe the foot ring and the lid seat while the glaze is still damp. Dry glaze crumbles; damp glaze wipes clean.
- Rest the pot on a stilt or a waster so a run lands somewhere harmless.
If a run survives the firing, wet silicon carbide paper will knock it back without gouging the surface around it. Work slowly and keep the paper wet.
Stuck Lids
This is the one that ruins an otherwise good teapot. Glaze on the gallery fuses to glaze on the lid flange, and now you own a sculpture.
The cause is usually clearance. Glaze adds thickness to both surfaces, so a lid that fit nicely in the greenware stage will be too tight once it is glazed. Teapot lids should feel slightly loose before the first firing, with a little more play than instinct suggests.
Wax the gallery ring and the lid seat, or wipe them clean with a sponge right before the pot goes in. Fire the lid in place but rotated a few degrees from where it sat, or prop it up on three tiny wads of clay so the two surfaces never touch. If a lid does fuse, tap the edge with a wooden mallet. Never lever it with a screwdriver; you will chip the rim and lose the fit for good.
Clogged Spouts
Glaze runs into the bore and fills it, sometimes right to the tip. The pot looks perfect and pours nothing.
Wax the inside of the spout before dipping, and pour glaze rather than dunking the spout end if the form allows it. Immediately after glazing, run a pipe cleaner or a twisted paper towel through the bore and check it against the light. Don't forget the strainer holes inside the body, which fill with glaze just as easily; a needle tool clears them before firing.
If a thin film survives the kiln, ream the bore gently with a drill bit turned by hand or a round file. A spout that tapers slightly and stays smooth on the inside will clear faster and pour cleaner for the life of the pot.
Problems on the Inside
The interior is where teapots get judged by use rather than by eye. Pooling glaze at the base, bare patches near the rim, drips running down the wall, and crazing all show up here first.
Pour-and-drain the interior rather than dipping it. Swirl the glaze, count a steady few seconds, then drain it back into the bucket through the spout and the rim. Give the inside a thinner coat than the outside; it only needs to be a sound liner, not a second skin. Matte glazes look lovely on a teapot's exterior and behave unpredictably inside, so keep the liner simple unless you have tested it.
Crazing is a fit problem, not just a cosmetic one. Crazed surfaces in a pot that holds hot liquid are harder to keep clean and can release material from a poorly formulated glaze. Use a liner glaze you know is made for food contact, and test new recipes rather than assuming. If you sell your pots, it's worth checking the food-contact rules where you live before you ship a batch.
A Short Routine Before Every Glaze Load
Most of these faults come from the same handful of causes: dust, thickness, clearance and speed. A five-minute routine catches nearly all of them.
- Sieve the glaze and check its thickness.
- Wax the gallery, the lid seat, the spout bore and the foot.
- Handle the pot with clean hands or gloves only.
- Apply thin coats, drying between each one.
- Wipe every seat and mating surface while the glaze is still damp.
- Fire slowly at the start and soak at the top.
Then write it down. A notebook line for each pot — body, glaze, how many coats, firing, result — is the cheapest tool in the studio. After a dozen teapots you will spot your own pattern: the pinholes that follow a rushed bisque, the crawls that follow a muggy afternoon, the lid that stuck because you were in a hurry at the wax pot. Fix the pattern and the teapots take care of themselves.
Photo: kummod / Pixabay
