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FIRING OF VIKING AGE CERAMICS

Artefact type: Reconstructed clay vessels in an experimental firing.

Use: Pre-heating of pottery prior to the actuall firing process.

Location: Krookila.

Period: Modern.

Dating: 1997 A.D.

Photographer: Jari Näränen

It is essential that the clay vessels have dried thoroughly prior to the firing. The best result is obtained by drying the pottery slowly in a cool, medium dry atmosphere where there is no draught. Thus the drying process can proceed evenly and the cracking and bending of clay is reduced to the minimum.

In order to allow any remaining free water to evaporate prior to the actual firing, the pottery is set to warm up next to an open fire. During the pre-heating process the free water molecules will evaporate and leave the clay slowly and peacefully, using the natural channels left in the clay body during the drying process. During the heating procedure special caution should be taken as to insulate the unburned clay vessels from any exterior moisture source, such as damp ground, in order to inhibit them to take in additional humidity.

Should there be any free water present in the clay body during the actual firing process, the extreme effect caused by the boiling water to vaporise and to escape from the clay body is likely to cause the vessel to break. The risk increases if the pores in the clay body are small and the structure is tight (caused by for example polishing the surface).

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