A ready-to-use primer intended for ULTRASILICA and AZURO silicone facade paints. It can be used on typical construction bases, also those covered with acrylic paints, also for renovation purposes. It does not contain solvents. It strengthens chalking substrates and levels their absorbency. It is very permeable to water vapor and improves the hydrophobicity of the paint coating. It limits the formation of efflorescence.