Louhisaari lime kiln

experimental project

from 2023

Louhisaari Castle, Askainen

Senaatti

 

It has proven difficult to repair old brickwork with modern mortar. In 2023 a lime kiln was planned, built, and tested, with the goal to manufacture mortar that is equivalent to old mortar, in terms of properties and durability. In the lime kiln, located in the garden of Louhisaari castle, limestone from Parainen was burned. The heated lime was turned into slaked lime by adding water and mixed with sand according to tradition. The grey coloring was achieved with carbon black. The lime mortar was successfully used to render the kiln itself. Some smaller brickwork tests were also made. Nordic collaborators and thin section surveys made on mortar from the 1600’s contributed with insights to the process. The project will continue with more testing and systematic analysis of the mortar.

The kiln was built by Restart and Muurasliike Johansson.

The limestone was delivered by Nordkalk.

The cycle of lime. Limestone (calcium carbonate) is heated to quicklime (calcium oxide), which is turned into slaked lime (calcium hydroxide) by adding water. The lime mortar will then slowly carbonize in the wall.
The lime kiln without its hat before ignition.
The kiln is filled with limestone with wooden rods in between, which functions as flues.
The burning went on through the night.
Brick hard limestone turns into brittle quicklime when heated.
Crushed quicklime, to which carbon black and sand will be added next.
Quicklime covered with sand is carefully made into slaked lime by adding water.
The process of turning quicklime into slaked lime is starting, and some of the water is boiling away.
When enough water has been added, the mixture will be stirred into mortar.
The first test done with the lime mortar was rendering of the lime kiln itself.