Month: November 2020

Station Lunda – Painted with Clay

THE MAIN BUILDING AT STATION LUNDA is now newly paneled and is supplemented with an outer panel lining around windows and doors. This has since been painted with clay paint. This is a paint that is little known, but that has an ancient origin.

In this case, the paint of the walls consists only of clay and nothing else. The clay is excavated from the Uppsala plain's reservoir of blue clay in a riverbank close by. It has then been slurried to filter out sand and coarser particles and has then been diluted with water to a suitable consistency. It is important to keep the fine particles. It is the nanoparticles in the clay that make it adhere to almost everything. I have even painted over smooth plastic and found it to stick there better than any paint on the market. The fine particles in the clay hold the color together and penetrate an outdoor panel of sawn timber. It is to some extent also possible to paint on a planed surface, but it then has less weather resistance. I have painted the underside of the porch roof and the eaves with the clay paint on that planed surface and it remains well because it is a protected surface.

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The Lunda Wood Stove

THE LUNDA STOVE came about in an attempt to improve the wood stove in general and to create a stove that could be built on-site and that also would improve both combustion and heating efficiency. It took a year to plan and build this stove. The result was very good. It is perhaps one of the world's best wood stoves with very high efficiency and the smoke is invisible and odorless when fired properly, except for a short time when ignited, which indicates very low emissions.
The Lunda Stove has a concrete frame. But so that it would not be too heavy, many tests were done with lightweight concrete mixtures that were subjected to fire tests. Once the concrete mixture was determined, molds were built to cast the outer casing in a single piece. This was done so that the stove would be completely smoke-tight. The interior is a rather complicated network of walls and ceilings that allows supply air to be taken in from the outside through a hole in the floor and which can then be taken directly into the combustion chamber floor or redirected so that it instead enters from the combustion chamber roof. The stove was designed to allow for reverse combustion when the supply air to the combustion chamber is taken from above and the flue gases pass out through the bottom of the combustion chamber and then pass on its outside and up to the convectors.
The combustion chamber is very well insulated to provide a high efficiency by allowing high combustion temperature. The principle of the stove is to first burn all gases as well as possible, and only when they have burned, take out the heat in the remaining flue gases. Most stoves are built so that the heat radiation from the hearth itself will contribute to the heating in the room. With this principle, you get worse combustion because there are heat losses in the combustion chamber and lower combustion temperatures.

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