Waterproof and Breathable

But on leaving the building, it is immediately obvious how time has slowly but inexorably ravaged this Wesel landmark, with algae and lichens covering parts of the basalt base. Dust and dirt from the air have over the centuries discolored some windowsills and cornices to gray or black. But now a product from Evonik’s chemistry labs will eradicate the marks of time and also protect the Cathedral over the next few decades.

TEGO Phobe is the name of this product, a special active ingredient for formulations to protect large buildings or small single-family houses against water. Its special feature is that in silicone resin paints and waterproofing formulations the product repels rainwater; it does not, however, seal the stone but allows water vapor to escape from the interior to the exterior. "The principle‘s the same as for a Gore-tex® jacket," says Jürgen Kirchner, an Evonik engineer. "Drops of rainwater bead off, but the far smaller molecules of water vapor penetrate through the pores of the stone from the interior to the exterior of the basalt." This allows moist masonry to dry without fresh moisture penetrating from the outside. The method sounds simple enough but underlying it is a fund of chemical expertise acquired through years of research, as quickly becomes evident during a tour of Evonik‘s Essen site where special additives for paints and coatings are developed. TEGO Phobe is industrially available as a milky emulsion or solution, which is then formulated to the end product, silicone resin paint or impregnation.