Fire damage of trachyte: investigations of the Teplá monastery building stones
Stephanie Gillhuber, Gerhard Lehrberger, Jürgen Göske, 2010. "Fire damage of trachyte: investigations of the Teplá monastery building stones", Natural Stone Resources for Historical Monuments, R Přikryl, Á Török
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The building stones of Teplá monastery (founded 1193) experienced a huge fire in 1677. Trachyte as a major rock type responded by changing colour from light beige to pink-red. Laboratory tests, during which the fresh unaltered stone from the original quarry was heated, proved the same reddened surface. Three varieties of local trachyte were examined: a greyish, naturally very fresh type (TA), a yellowish, slightly weathered and therefore iron hydroxide-bearing type (TB) and a trachyte typical with black manganese oxide dendrites and patches (TC). The changes of the physical properties and composition of these rocks were examined by ultrasonic velocity, thin section analysis, SEM observation and XRD tests. The experimental studies showed that Teplá trachyte is generally fire resistant up to 1000 °C.
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Natural stone is considered to be a versatile, durable and aesthetically pleasing building material. From the beginning of civilization, important structures and monuments have been built from, or based on, natural stone. Until the end of the nineteenth century, the use of local stone resources was mostly in balance with the local environment. Strict environmental legislation has resulted in the closing of many long-standing quarries in industrialized countries, which has led to a shortage of traditional stone varieties. This has caused problems for restoration practice. Cheap, imported stone from less industrialized countries has become more widely available in recent years.
Some of the issues related to built stone conservation and restoration covered by this volume are: the establishment of inventories of possible replacement stones; understanding the decay mechanism and use of preventive conservation methods for slowing down decay processes; evaluation of the properties of natural stone; and assessing the risks of using replacement stones of different qualities.