Reactive Concrete Acid Stains contain inorganic salts dissolved in water that penetrate deeply, creating a durable and permanent color. Perfect for patios, building exteriors, driveways, garage floors, residential projects, and sidewalks, the stains can be applied by spraying, brushing, or rolling. Each gallon stains approximately 200 to 300 sq. ft., depending on the porosity of the concrete. Triple-S Chemical Products Inc. 800-862-5958.