When the substrate is painted with an oil paint, it is always necessary to remove it. The paint can be removed mechanically (scraping, knocking off), thermally (burning) or chemically (with a special agent). Bear in mind, that the substrate might be weakened by using chemical agents or heat. It may become necessary to strengthen the surface with ALPOL AG 700 deep-penetrating primer or ALPOL AG 707 silicate-polymer primer for mineral substrates. Paint residual on the substrate may cause the tiles to fall off the wall after some time. Adequately treated surface, free from paint, dust, dirt, oil, grease etc. is the guarantee for proper bonding strength of the cladding being fixed. The following tile adhesives are recommended: ALPOL AK 515 flexible for porcelain tiles, ALPOL AK 513 flexible ALPOL AK 512 quick-setting flexible adhesive, characterised by increased flexibility and bonding strength, to guarantee that the tiles will not flake off the wall.