These are paste-like cleaning agents that contain a carrier material and active cleaning substances. When applied, they dissolve impurities in the substrate, which are taken up into the compress together with the solvent used, where they are bound. Once the cleaning process is finished, the compress will be almost completely dried out. These pastes can be used with a range of different active substances, e.g. for removing tar stains, rust spots, gypsum crusts, greasy deposits, heavy metal residues, etc.
Clean Galena is one such emission-free cleaning compress. It contains no ammonium carbonate nor EDTA. Various readily biodegradable complexing agents that are used in the food industry (substances that can bind various metal ions, such as iron, copper, lead and other heavy metal ions) are used as active agents. They are combined in a manner that further increases the cleaning effect of each individual active ingredient. The carrier material is bentonite, a layered silicate that binds various dissolved substances and colloids through adsorption and electrochemical processes. It also regulates moisture transport during the cleaning process, with the help of a small amount of cellulose. After one day – or a little longer at very low temperatures and high humidity – the compress will dry out and detach from the substrate. Once removed, the dried material must then be disposed of according to the applicable local regulations. Here, it is only the dirt removed from the facade that needs to be considered, not the compress material itself.
A variety of laboratory tests also show that Clean Galena has a high potential for cleaning not only on natural stone substrates, but also on dirty bricks.
Further information on emission-free cleaning of historic natural stone surfaces can be found in our brochure.