FAQs - Wacker Chemie AG


If You Have Questions about Silicone Resin Emulsion Paints, This Is Where You Will Find the Answers

We have compiled the answers to the most frequently asked questions on silicone resin emulsion paints in the following section.

All facades contain flaws (e.g. hairline cracks). These are weak spots, where moisture can penetrate into the facade. The substrate must be able to dry out whenever ambient conditions permit. Otherwise spalling, or other damage, will occur. Additionally, dry substrates do not promote the growth of microbes, such as algae and fungi.

Silicone resin emulsion paint is a mineral-like coating and is accordingly just as breathable (water-vapor permeable) as silicate paint and whitewash. The reason for this is its microporous structure, which permits free movement of gases. In the 3-class classification used in European standard ISO 7783-2 for water-vapor diffusion current density, silicone resin emulsion paint falls under Class 1 (highly permeable).

Due to the low water uptake, as little water and moisture as possible penetrate into the facade. However, no exterior paint offers 100% protection against damp. That’s why it’s important that the paint system features high water-vapor permeability. This is the only way that water in the facade can dry out again – the masonry can “breathe.”

The combination of these two properties makes silicone resin emulsion paint the prime coating system for facades, and is the reason for their extremely high durability and dirt-repellent effect.

The beading effect of silicone resin emulsion paints is apparent during weathering (rain, snow, etc.) and is retained throughout the coating’s service life. A treated facade thus keeps its perfect appearance even after many years.

The beading effect can be witnessed, in particular, when it rains: water droplets bead up into little balls and roll off the silicone resin emulsion paint, thus preventing the formation of standing water. This effect also ensures the appropriate waterproofness. Waterproofness is the property of preventing standing water from penetrating into the substrate even after an extended period of time.

Silicone resin emulsion paints owe their great durability to the properties of low water absorption combined with high water-vapor permeability. These properties are conferred on the paints by the silicone resin binder, which forms a strongly hydrophobic (water-repellent) network, penetrating deep into the structure of paints and plasters. This permanently protects it against UV light and washout.

Dry facades are less prone to attack by algae, fungi and mold than damp ones. Mineral-type coatings are less susceptible than thermoplastic coatings. Silicone resin emulsion paints keep facades dry. They are non-thermoplastic, mineral-type coatings and thus provide protection against the growth of microorganisms. For facades that are highly at risk, there are silicone resin emulsion paints that contain additional protection against microorganisms.

The binder in silicone resin emulsion paints comprises 50% mineral-type silicone resin and 50% polymer emulsion. The paints thus combine the useful properties of organic and mineral coatings in a single system.

Silicone resin emulsion paints have been used successfully for 40 years. More than a million buildings all over Europe have been coated with these paints, and many of them have endured over 20 years without needing any further renovation.

Provided they are suitably prepared and cleaned, all kinds of paint can be overpainted with silicone resin emulsion paint (see also Question 16), including firmly adhering emulsion coatings. However, to avoid compromising the silicone resin emulsion paint’s breathability, old coats of emulsion paint should be stripped off or removed mechanically.

As a rule, freshly plastered facades cannot be painted until the plaster has set (carbonation), which usually necessitates re-erecting the scaffolding. Silicone resin emulsion paints, by contrast, can be applied to fresh mineral plaster right away, since they are highly permeable to CO2 and do not impede carbonation (CO2 permeability guarantee).

Substrates with salt damage must always be properly repaired first: remove all of the damaged substrate, apply repair plaster and a silicone primer. Then you can paint the facade with silicone resin emulsion paint.

The paint/substrate interface is the Achilles’ heel of any coating system. This is why a silicone primer is so important for the effectiveness of the paint coating. It creates a dry zone under the paint and thus prevents substances such as alkalis and salts within the construction material from damaging the facade.

Thermal insulation causes a change in surface physics. The facade is heated by the sun from the outside only. At night, it cools down. Condensation may be produced, exposing the facade to more moisture than a non-insulated one would be.

This nocturnal moisture-induced stress, combined with the fact that the insulation layer reduces the heat flow from the inside out, slows down the rate of drying. As a result, algal growth is often promoted. Thanks to their excellent diffusion properties, silicone resin emulsion paints achieve a significant improvement in such cases.

All coatings containing a wetting agent (emulsion paints and silicone resin emulsion paints) will adhere to silicone resin emulsion paints, but silicate paints and whitewash will not.

No (see also Question 10). You merely need to clean the facade, remove any loose particles and, ideally, treat it with a silicone primer. This also applies to old mineral coatings (silicate and organosilicate paints and whitewash).

The quality of an exterior paint is measured by the length of time it protects the facade from external influences and keeps it looking perfect. Slicone resin emulsion paints are unparalleled in these respects, which makes them much more economical in the long term.