HMK® S741 Stone Hardener – 10 liter


SKU: HMK-S741-10 Category:



For interior and exterior use on weather beaten, crumbly and worn-out sandstone and other soft, highly absorbent mineral surfaces. Surface treated with HMK® S741 remains 100% vapor permeable, UV resistant, and leaves a natural appearance. Not effective on marble and most limestone.


The stone must have no less than a 5% absorption and be at least 3/4 inch thick. Temperature must between 40-75 F.


All loose layers, crusts and particles must be removed prior to application of the S741 because they can not be re-bonded. Apply to a clean and dry surface with HMK® Z170-171 Sealing Brushes, a natural bristle brush, or roller. Several, wet on wet, applications should be made until complete saturation is achieved. Protect the surface from rain and heavy sunlight for one week to allow humidity to successfully polymerize S741 into (SiO3) Quartz. Complete hardening is achieved 2-3 weeks after application. Impregnation with HMK® S31 Silane Impregnator is recommended because hardening process does not provide protection against water and dirt.


Depends on surface, 1-5 liters per 11 sqft. (1 square meter)


Chemical product. Contains Turpentine Substitute Flammable. Keep away from heat, sparks and flame. Harmful or fatal if swallowed or inhaled. Use with adequate ventilation. Avoid eye/skin contact, breathing of vapor or mist. If exposed, wash/flush with water. Get immediate medical attention. Keep container secure and away from children. See Material Safety Data Sheet.


1/4 liter cans (8.5 oz.) 25 per case, 1 liter cans 34 (oz.) 12 per case, 5 liter cans (5.68 qts.) 4 per case, 10 liter cans (11.36 qts.) 2 per case.


Store in cool place. Keep lid tightly closed.


Always test product in an inconspicuous area and in actual installation to determine number of applications necessary to achieve proper hardening. In the case of extremely damaged stone, repeat S741 application in three weeks increments.


Limitation of liability: The liability of HMK® for defective products and any claims for damages whatsoever is limited to the purchase price of the products. HMK® shall not be liable for any consequential damages. No other warranty or representation is made or implied.

Additional information

Weight 20 lbs
Dimensions 14 × 9 × 6 in