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Kateriin Ambrozevits

  • Faculty of Art and Culture
  • Cultural Heritage and Conservation
  • BA
  • Dry-ice blasting for wooden architecture
  • Tutor: PhD Maris Mändel, PhD Urve Kallavus (TallTech)

This thesis presents an overview of the various methods of cleaning different surfaces. The method of dry-ice blasting, primarily focusing on cleaning air pollution residue and even finishes from wooden architectural elements, is explained more thoroughly.

Maintenance of monuments demands more attentiveness and preparation than usual. Cooperation between the operator of the equipment and the conservation specialist is paramount. It would also be beneficial to conduct some pre-studies to determine the specific attributes of the particular object – e.g. wood species (some are softer than others), the number of layers of finishes and so on, in order to ascertain their mutual effects.

Determining the paint types with infrared spectroscopy
Counting the number of layers of paint

After theoretical research empirical tests were performed on three wooden objects from historical buildings which were treated with a dry-ice blaster. The object was to determine if and in which conditions it is possible to clean a relatively soft wooden surface from accumulated residue (such as air pollution) or finishes while concurrently not damaging the surface itself and preserving historic tool marks or even the first layer of paint.

Dry-ice pellets
Removing finishes

The analysis of these tests was supported by laboratory research which enabled to understand the treated materials (tree species, paint types) and the effects of dry-ice blasting on the surface structure.

Determining tree species – spruce
Scanning electron microscope image of tangled wood fibres illustrates how important it is to determine the right work methodology

Unfortunately the right equipment can not yet be found in Estonia for treating wood with no concurrent surface damage. Yet there are options available even when they have not been originally designed for delicate surfaces – cleaning everyday smudges off round logs, especially when done indoors and even without the aim to cover up later or cleaning off lightly attached finishes with the intention to repaint is feasible when done on objects other than monuments.