Asbestos-ceramic is a type of pottery manufactured with asbestos and clay in Finland, Karelia and northern Scandinavia c. 1900 BC–200 AD. These pottery exhibit adiabatic behaviour. A certain vessel-type with insulating properties is also sometimes called asbestos-ceramic although it does not contain any asbestos.
The most probable origin of this style of ware is the shores of lake Saimaa in Finland, which is the only place for richer easily accessible natural deposits of asbestos in its area of distribution. Finds from inland Finland are the oldest. In Finland real asbestos-ware is known from ca. 3900–2800 BC to ca. 1800–1500 BC. In northern Scandinavia, asbestos ware appears apparently from ca. 1500 BC to ca. 500 BC.
Asbestos ware is usually classified under comb ceramic ware. From the times of the earliest comb ware (ca. 5000 BC) in Finland, asbestos was mixed with clay as an adhesive. At some point, people started to make use of the characteristics of asbestos: its long fibres allowed large vessels with thin walls, which made them lighter, without compromising durability. Some of the vessels had 6 mm thick walls with a diameter of around 50 cm (Pöljä-style). The ware is divided into the following styles (Finland):
- early asbestos ware:
- Pit-comb ware with asbestos
- Kaunissaari ware
- main styles:
- Pöljä ware
- Kierikki ware
- late asbestos ware:
- Jysmä ware
There are two variants of asbestos-pottery depending on its asbestos amount. Asbestos pottery had an asbestos amount of 50–60%. It is usually found along with evidence suggesting metal work, i.e. crucibles, moulds, slag, fused clay, artefacts of bronze and copper and stone sledge hammers. There are a few finds of pure copper artifacts among asbestos ceramic finds. These include a bracelet and a hatchet (Finland) and some pieces of copper (Sweden). Asbestos ceramic may also have been used as a heat-storage medium. The vessel patterns are identical to the Neolithic and Bronze Age Jōmon culture in Japan (jōmon = rope pattern). The most common patterns, however, are the comb and pit decorations typical of North-Eastern Europe at the time (Finland).
The term asbestos ware refers to vessels containing 90% asbestos and 10% clay. Asbestos ware can resist heat up to 900–1000 °C. The clay made shaping of the vessel possible, but the high amount of asbestos does not classify it as pottery in a formal sense. It is believed that the asbestos ware was used in iron production such as spearheads, arrowheads and artefacts. The vessel is also drilled with many holes. The fact that the reduction of iron ore (FeO3) with abundant carbon generates large amounts of carbon monoxide (CO) may suggest that the drilled holes were used to increase the influx of air (oxygen) required for proper glowing process. Iron ore is abundant in lakes e.g. in Finland.
Lastly, the term hair-temperature pottery refers to ware made of fine, sorted clay tempered with about 30% finely cut hair and chamotte with similar shape, size, and surface treatment (including decoration) as the asbestos pottery. It does not generally contain asbestos, but some samples have small traces. Hair, when used as ceramic temper, leaves thin pores in the ware after firing. Its intended use is unknown, but its adiabatic capacity suggests some kind of insulating usage (but not heat resistance).
The analysis made by University of Lund, Department of Quaternary Geology, on asbestos pottery was quite unexpected, since this part of Northern Europe, usually considered to be a step behind the rest of Europe, actually introduced iron production in the pre-Roman Iron Age.
The style seems to disappear around 200 AD in Finland but continues in Scandinavia. The disappearance is thought to be related to the transition to a semi-nomadic reindeer husbandry lifestyle.
- Hulthén, Birgitta, On Ceramic ware in Northern Scandinavia during the Neolithic, Bronze and Early Iron Age (1993).