Kiehl Impranet Kiehl impregnating for stone, solvent free 5L Impranet is a stone impregnator that can be used on both exterior and interior surfaces. Impranet penetrates deep into the pores and, once cured, protects the treated surface from water and oil penetration. It prevents frost damage, prevents the growth of algae and moss and softens the effects of weathering on permanently wet surfaces. It contains no organic solvents and has a neutral odour. Thanks to its innovative formula, it is also excellent for use inside buildings.