Powerwashing alone does not take the red dirt stains out. Why are red clay stains so hard to clean from concrete and masonry? Possibly because what gives the reddish color of the dirt is iron oxide or better known as rust, which is highly insoluble in water. In fact, iron oxides are often used as inexpensive earth tone pigments in coatings, paints and colored concrete.
The process to remove red dirt stains is a chemical (cleaner) and mechanical (power wash) combination. An acidic based cleaner is more powerful because it will bubble up the red clay that is deeply imbedded in the concrete. Yet, one has to be careful as not all acid cleaners are equal. Straight acids (or highly concentrated) may be too powerful and actually burn or harshly etch the concrete. If an acid cleaner is diluted too much, then its not going to break the bond the iron oxide has made to the masonry or concrete.
Our balanced Red Clay Stain Remover is buffered with water and surfactants to only micro etch the concrete, thus removing the red clay but not adversely affecting the surface. Apply the Red Clay Stain Remover using a hand pump sprayer, let sit for 3 to 5 minutes and then power wash off. It's important to use a power washer so that you move the clay completely off the surface. Otherwise the red clay may resettle in another area. The picture below (compliments of Dionne Thompson of Detail Pressure Washing in West Union, SC) shows our cleaner taking off red clay stains from a brick foundation wall.
After cleaning the surface, consider using our Trojan Masonry Sealer that will permanently penetrate the surface without changing the look of the exterior. It will make future cleanings much easier as the red clay cannot absorb into the pores.