How do I use SILRES® WH?

SILRES® WH is usually diluted 1:4 to 1:9 with water for direct application to wood. SILRES® WH can also be added undiluted to waterborne stains in concentrations of up to 3%.

Can SILRES® WH reduce the use of biocides?

Yes. Using SILRES® WH provides long-lasting protection from water and water-related damages. That opens up the door to reductions in the use of biocides, especially fungicides. In the case of many biocides, it eliminates their use entirely.

Can wood be painted after impregnation with SILRES® WH?

Wood treated with SILRES® WH can in principle be painted, if some weathering of the impregnated substrate is allowed first. However, it is important to note that smooth wooden surfaces will absorb only some of the silicone – the rest remains on the surface. As a result, and especially in the case of highly concentrated wood preservatives, paint adhesion may be restricted and leveling impaired. For this reason, SILRES® WH should not be employed as a primer.

Will beading be visible right away?

Yes, but the beading effect becomes visible best after it has been exposed to the elements for a while (approx. 2 weeks). Thanks to SILRES® WH, however, beading will then be visible for an unusually long time.

Does SILRES® WH keep wood from graying?

No. SILRES® WH does not prevent graying, because this is caused by UV radiation, which silicones are transparent to. SILRES® WH does, however, help make graying uniform.

Is SILRES® WH compatible with acrylic resins?

SILRES® WH has been combined with different acrylic resins. So far we did not see any incompatibilities. As typical for combinations of organic resins with silicones the dry film appears hazy, but that has no impact on the product’s properties.

Is SILRES® WH compatible with common pigments?

Pigmented wood coatings/wood stains can be modified with SILRES® WH (1–3% dosage level) without any problems – therefore no compatibility issues are expected.

How much SILRES® WH can/should be used per m2?

Application trials on spruce have shown an approximate amount of 100 g/m2 of the diluted product (e.g., 1:9) to be sufficient. Of course, the precise amount best used depends strongly on the absorption capacity of the wood.

Can SILRES® WH be used for temporary wood protection (e.g., on freshly sawed wood until construction)?

Basically yes – a dilution of 1:4 to 1:9 should be useful for the protection of construction timber. However, we have no certificates for SILRES® WH in this regard.

What is the maximum wood humidity at which SILRES® WH can be applied? (The recommendation for standard wood protective coatings is 25%, but there are products for 40% wood humidity available.)

We have no figures on this. But with SILRES® WH being a water-based product, it is to be expected that high wood humidity will limit/reduce the penetration depth.

What is the penetration depth of SILRES® WH into the wood substrate?

The penetration depth strongly depends on the type, density, and natural resin content of the wood. Also the penetration depth is strongly influenced by the method of application – grain-cut timber/fiber direction.

How does the combination of SILRES® WH with a biocide or alkyd resin/biocide complex affect the product’s penetration depth?

Whether or not the penetration depth is influenced in any way is unknown at this time.

Which tests have been conducted regarding product performance?

We tested SILRES® WH as it is (not combined with other products). The focus of our trials was the durability during weathering. The outdoor weathering showed very good visual beading and low water absorption after 17 years of natural exposure (video clip, trial with Karsten tubes). Mainly though, we use a QUV-B chamber and observe the impact of weathering on the beading effect (the weathered wooden stripes on our demo-tool for the ECS have been weathered in a chamber).

Which light frequency/light spectrum is applied for the tests?

To date we have used UV-B light with frequencies from 280 to 315 nm. The main frequency is 313 nm. Future tests will involve UV-A irradiation with frequencies of 315 to 380 nm and a main frequency of 340 nm.

Does SILRES® WH improve the cracking resistance of the substrate?

SILRES® WH maintains the wood breathability on a high level, meaning shrinkage and expansion will not be completely prevented. However, since the silicone resin is flexible it will not flake off due to shrinkage or expansion. Also the silicone resin reduces the amount of moisture absorbed and therefore keeps shrinkage and expansion at a lower level. This has a positive influence on the cracking tendency.

The brochure mentions that with SILRES® WH wood is effectively protected for up to 17 years. Can you confirm the dilution rate for this (1:4 vs. 1:9)?

We worked with both dilutions. The 1:9 dilution even shows slightly better results in terms of the visual beading effect. In the video regarding the wooden façade, the panels on the left are treated with a dilution of 1 part SILRES® WH to 9 parts water.

Does SILRES® WH change the appearance of timber when applied? If so, does this differ depending on the type of timber?

We tested for a change of appearance on spruce, oak, beech, and ash. With a 1:9 dilution there was no or only minimal influence on the appearance (slight darkening).

Has SILRES® WH been tested for fire repellency and smoke/fume emissions?

So far this has not been tested, but the reaction to fire will be examined in our labs. In this respect, it is important to note that silicone resins generally do have a high resistance to fire. They are, for instance, also used as binders in heat-resistant paints. The first positive feedback was given for the use of SILRES® WH in intumescent coating for wood.

TDS mentions the product increases the longevity of stains/coatings because of hydrophobicity effects. Can we assume this applies to both solvent-based and water-based stains and coatings?

SILRES® WH should only be used in water-based stains as it is an emulsion. We are, however, already working on solvent-based versions as well.

Can SILRES® WH be used to replace waxes?

Yes, because SILRES® WH has outstanding durability and is not decomposed by weathering. This is why we regard it as a very good solution for replacing waxes.