Reactive Acid Concrete Stains react with the minerals in your concrete to physically change the color of your concrete. With RAC Reactive Acid stain you will create a colored translucent, variegated and sometimes marbleized effect that will be unique and elegant. No two pieces on concrete will ever color exactly the same; the texture of concrete, age and dilution ratio affect final color appearance. The translucence of RAC Stain also allows the many unique characteristics of the concrete to show through. Staining your concrete will transform it into a work of art.