The correct preparation of the subsoil is a very important issue. Professionals know the basic rule for substrate preparation: The surface to be treated must be dry, load-bearing, evenly absorbent, clean and smooth. However, because ideal conditions are rarely found in practice, floors, ceilings and wall surfaces must first be thoroughly inspected. This is the only way to play it safe during pre-treatment. Various methods are recommended for further substrate testing: - Testing for moisture Dark discolorations on plaster or concrete surfaces as well as moulds and mildew stains indicate moisture. Where doubts exist, the foil sample provides clear results: After 12 to 24 hours, residual moisture can be seen in the form of condensation behind the film. Of course, the test can also be carried out with a moisture meter, which provides proof of the moisture values ? especially in border areas ? Before starting any further work, the substrate must always be dry. - The surface strength can be ideally determined with the scratch or pressure test: If parts of the surface burst out under moderate pressure with a hard, angular object, the substrate is often not strong enough for wallpapering. If chalking abrasion is detected when rubbing the surface by hand, this surface must first be carefully cleaned and, if necessary, solidified with a water-based wallpaper base. Old dispersion paints can be tested for their load-bearing capacity by means of an adhesive tape test: To do this, stick a strip of adhesive tape onto the substrate, press firmly on and pull off with a jerk. If clear parts of the paint stick to the tape, the paint should be removed. - The absorbency of ceilings and walls can be tested simply by wetting them with water: If the water beads off, the surface is non-absorbent or only slightly absorbent. If the substrate shows a rapid absorption of water or if the surface quickly turns dark, this is an indication for highly absorbent substrates. Fine hairline and mesh cracks will also appear. This information is certainly not complete and no warranty claims can be made. We just want to give you some tips and suggestions. If you have any questions before placing an order, it is best to call our application technology department for advice.