HMK S731 Silane Impregnator

HMK S731 is intended for absorbent soft and hard natural stone, artificial stone, concrete, and unglazed brick. It can be used on compatible interior or exterior surfaces. Because absorption differs by material, HMK recommends testing an inconspicuous area to confirm suitability, coverage, performance, and appearance.

The silane-based formula penetrates the absorbent material and reduces the entry of water and dirt. By limiting water absorption while allowing vapor movement, it protects from within rather than creating a decorative finish on top of the surface or changing its appearance.

HMK S731 leaves little to no aesthetic change on properly treated surfaces. It is intended for customers who want water-repellent protection without color enhancement, gloss, or a visibly altered finish. Always test first because absorbency and appearance can vary across different materials.

HMK specifically states that S731 reduces water and dirt penetration and helps reduce potential frost damage. The manufacturer does not identify it as protection against oil or grease, so customers needing oil-stain resistance should select a sealer expressly rated for those contaminants.

Yes. HMK S731 is vapor permeable, allowing moisture vapor to continue moving through the treated material. This breathable protection is useful on absorbent mineral surfaces where reduced water penetration is needed without trapping normal vapor transmission within the stone, concrete, or brick.

Yes. S731 is suitable for both interior and exterior surfaces. By reducing water penetration into absorbent material, it also helps reduce the potential for damage associated with freezing moisture. Exterior surfaces must be protected from rain and humidity for three days after treatment.

No. HMK identifies S731 as a silane-based impregnator, and its safety information states that it contains a turpentine substitute and is flammable. It is supplied ready to use, but adequate ventilation and separation from heat, sparks, and flames are required during application.

The surface should be chemically clean and dry before treatment. HMK recommends cleaning with diluted R155 Intensive Cleaner, flood rinsing, and allowing at least 24 hours to dry to 6 to 8 percent residual moisture. Apply one or two thin, even, wet-on-wet coats and remove excess before it dries.