Station: [4] Firing

Now, the heat is on.

About once a month, the kiln is fired up. Kilns like this one – though usually twice as big – were common in Bürgel from the Early Modern period until the first decades of the 20th century.

For the firing process, the potter skilfully stacks the leather-hard – in other words, air-dried – “greenware” pots in the kiln chamber. The idea is to leave as little free space as possible. That’s because each firing uses up several cubic metres of wood, so it’s very expensive. The arrangement of the various pots needs to be carefully considered and precise, because they shrink, and this firing shrinkage is around 15 per cent. A mistake during stacking could lead to all the pots collapsing, ruining a whole month’s work. It doesn’t bear thinking about.

Once the kiln chamber has been filled, wood is added at the front and set alight. Then the kiln is bricked up, apart from two or three small openings. Throughout the entire firing process, wood constantly has to be added through these openings. They’re also used to toss in the smalt – the mixture that leaves the “blue apron” on the pots at the front. The more blue there is on a pot, the closer it’s stood to the flames, and the higher the temperature at which it was fired – and ultimately, the better the quality. Simple, really.

The temperature has to remain at the same level for around 30 hours by continually adding more wood. The pots are in direct contact with the flames. The highest firing temperatures are achieved at the front on the right, where the fire is, and at the top, where the heat gathers. That’s where the stoneware is produced. The pots standing farther back, where the kiln chamber is less hot, go on to become earthenware—which has a different colour, but also sounds different and is more porous than stoneware. While stoneware is only fired once, glazed pottery requires at least two firings: the first, known as the bisque firing, fixes the shape of the piece. The subsequent glaze or glost firing fuses the glaze to the pot. 

Very elaborately glazed pieces are bedded into two large dishes called saggars that form protective containers. Tripods and other pieces of kiln furniture are added to prevent the pots adhering to one another during firing because of the glaze.

After the firing is complete, the kiln and the pots are left undisturbed for roughly another thirty hours. Finally, the kiln can be opened and cleared out. If it’s opened too soon, and the temperature suddenly drops, the thermal shock can crack the pots.