Discovery of the Week 25

NEWS | Published: 9.7.2010

Pieces of limestone

The discovery of the week series presents pieces of limestone. Limestone appears naturally in very few areas in Finland. In Kimito (Kemiö) and Pargas (Parainen), limestone has possibly been quarried already in the Middle Ages. It was also imported to Finland from e.g. Estonia. Limestone was a significant element in medieval as well as later stone and brick building, for it could be burned into lime mortar.

Limestone, crushed into small pieces, was burned in temperatures of up to 1 000° Celsius for days. The resulting product was lime, which was still burning, and put out with water. After this, the dough-like mass could be improved by storing it in a hole in the ground for severeal years. Water, sand and the masoner\s special ingredients such as volcano ash were mixed with the lime mass in order to create mortar. After the brickwork was finished, the lime began crystallizing back to stone form. Burning lime required the work of a highly specialized craftsman. The burning lime could cause trauma in for example the eyes.

The pieces are most likely linked with the construction of the stone house next to the excavation site. The pieces suggest that at least part of the lime needed in the building process was not burned until at the construction site.

Archeological excavations 2010

Excavations are taking place inside the Aboa Vetus Museum once again
this summer. The museum features a part of the medieval Convent Quarter
whose inhabitants were mainly rich merchants and their servants. This
summer, the backyard of largest stone building in the museum area is
being excavated. The building dates back to 1401-1404.

Much is being expected from the excavations of the area because the
backyard has been used for various kind of activities in the Middle
Ages: animal care, gardening, housework and also the household waste was
thrown in a heap in the yard. Therefore, one can presume that remnants
of animals and vegetables as well as pieces of various items are found
in the area. The manure-rich soil layers of the yard also preserve
organic material, such as leather items, better than the ordinary clayey
soil layers. In earlier excavations next to the yard, the oldest wooden
structures of houses and the finest luxury goods in the museum area
have been found. The oldest soil layers date back to the beginning of
the 14th century, that is, the earliest phase of Turku. 

Each week, a new Discovery of the Week from the excavations is
displayed in the museum from June 11th to August 20th.