Ideal for both interior and exterior concrete polishing applications, H&C Clear Liquid Hardener & Densifier is a water-based silica solution that permeates concrete to form a durable, even surface. It works well on stained and dyed concrete, repels blushing and yellowing, and is easy to apply, maintain, and polish. Use it for showroom floors, retail outlets, warehouses, airports, and other commercial projects. H&C Decorative Concrete Products.