You can choose a paint colour by looking at a card. A potter firing celadon cannot simply point to a shade of green and expect the kiln to obey. In Longquan, Zhejiang province, traditional makers prepare a glaze, coat a vessel and watch it pass through carefully controlled stages of heating and cooling.
UNESCO says that over- or under-firing can spoil the effect. Makers use a thermometer and watch the colour of the flame. That detail is especially revealing: the fire is not just heat; it is information the craftsperson has learned to read.
Two results from one tradition
UNESCO describes different Longquan celadon finishes, including one with a crackled surface and another with a thick, softly coloured glaze. These are not defects and successes on a simple scale. They are styles produced through knowledge of materials and firing.
The craft has been passed through families and teachers. Its materials include mineral ingredients and plant ash, but a list of ingredients is not enough to make the bowl. How they are mixed, applied and fired matters enormously.
The second firing matters
The vessel and its glaze don’t begin as the same material. UNESCO describes the glaze being applied to a stoneware vessel that has already been fired, followed by another firing. The green surface is the result of further work on the object, rather than a colour painted onto a finished bowl and left to dry.
The account identifies six stages of heating and cooling in the repeated firing cycle. It also mentions temperatures reaching as high as 1,310 degrees Celsius. That figure helps explain why the process cannot be treated like changing the colour of an ordinary painted surface. It belongs to a specialist craft using a kiln.
A high temperature alone doesn’t tell the maker that everything is correct. The order of the stages matters, and so does knowing what is happening at each one. UNESCO describes using both a thermometer and the colour of the flame. One supplies a reading; the other supplies a visible sign that an experienced person has learned to interpret.
It is tempting to see a measuring instrument and assume that judgement has become unnecessary. Here, the description puts the two alongside one another. The person controlling the firing brings knowledge to the information the tools provide.
The finish also complicates an easy idea of perfection. A crackled effect may be part of a particular Longquan style rather than evidence that someone simply failed. To appreciate the result, you need to know what the maker was trying to produce. One smoothness test won’t explain every bowl.
Recipes passed through teachers and families carry part of that knowledge, but a recipe isn’t a guarantee. Preparing the glaze, applying it and controlling the firing all contribute to the final surface. The finished vessel lets us see the result of those decisions, even though we cannot read their entire sequence from its colour.
Would you trust the kiln?
Putting a carefully shaped bowl into a kiln brings another set of decisions. The maker still controls the process, but cannot see the finished object until the fire has done its part. There is skill in choosing the moment to stop, and some uncertainty that even experience cannot make disappear.
Longquan celadon can be an artwork or a usable vessel. That may be the nicest surprise: a beautiful result of a demanding process can still hold something as ordinary as tea. The paper made in Anhui offers a similar question about the work hidden inside an everyday object.
Look more closely at a glaze, then at the work of a porcelain city: Why is celadon green? and How many people make one bowl?.