Forty shared buckets, a dog-eared notebook and a narrow middle: glazing is measurement, not magic, and the liner glaze matters most.
The glaze shelf in our studio is a shared language and a shared argument. Forty buckets, each label corrected twice in two different hands. The black that goes green over a thick edge. The white that crawls if you look at it wrong. The tenmoku somebody decanted into a jam jar and never owned up to.
Learning to glaze in a shared studio means learning to read other people's results and not fall in love with them. A bucket is not a recipe, and the same dip on a different clay can come out a different colour entirely.
Thickness decides more than colour
Almost every glaze fault on that shelf is a thickness fault. Too thin and the surface is dry, patchy, or barely there after the firing. Too thick and it runs onto the shelf, crawls back from the rim, or shivers off the body in flakes. The middle is narrow, and the only way to find it is to measure the time you dip.
Count it out loud. Three seconds, five, eight. Write it down with the tile. The same glaze that pools at eight seconds can be a lovely eggshell at four, and you will never remember which was which without the note.
Water is the other half of that measurement. A bucket left open in a warm studio thickens by the afternoon, and the same four-second dip that worked at nine o'clock will be eight seconds by four. Add water before you start, stir from the bottom, and sieve the bucket at the beginning of each session rather than the end.
Keep the rim of the bucket clean. A crust of dried glaze on the lip drops into the mix in flakes, and a flake on a pot is a lump under the surface that no amount of sanding will hide.
The liner glaze is not optional
Anything that will hold food or drink gets a liner: a stable, glossy glaze on the inside, tested on the body it sits on. A beautiful matt exterior with a rough interior is a bowl that stains, and a glaze with a high metal content can be perfectly safe on a vase and wrong on a mug.
Our liner is a plain off-white, mixed in a small batch and kept on the top shelf where nobody borrows it. It is the least interesting glaze in the room and the one that matters most.
Test tiles and honest notes
Every new glaze goes on three tiles of the same body before it goes near a pot. One at the thickness I think is right, one thinner, one thicker. The tiles go through the kiln together, on the same shelf, and the notes go in the book with the date and the batch code.
The book is dog-eared and full of crossings-out. It is also the only reason the studio has four glazes that work reliably rather than forty that sometimes do. When a bucket is re-mixed, the page gets a new entry; a glaze is not a fixed thing, and pretending otherwise is how a good surface quietly turns bad.
Glaze does not forgive a rushed rim
Some glazes are also simply not for the shelves. A runny copper red that looks magnificent on a vase will weld itself to a plate and take the foot with it. Give those a catch tray and a footnote in the book, and think twice before putting them on anything that has to stack.
Wipe the foot. Wipe a thumb's width below the rim. Do not dip a pot straight from the damp cupboard. Do not stack greens and whites in the same firing without a catch tray underneath. These are not superstitions; they are the difference between opening the kiln and opening a bill.
And when a glaze comes out wrong, keep the tile. The shelf of failures is the best teacher in the studio, provided you wrote down what you did to earn a place on it.