How To Wash Cast Stone

We produce more than 6 million pounds of cast stone per year, and every piece of it ends up on a structure somewhere in the USA. Often, our cast stone is a principal architectural element of a new structure. Despite its eye-catching position, we often see installed stone that is just one wash away from a lifetime of absolute beauty. Best practices for washing cast stone aren’t often discussed, and many masons are fearful to wash the cast stone they install due to hearsay or fear of product degradation, burning, decreased durability or difficulties washing cast stone of deficient quality.

Additionally, there is some age-old confusion dating back to the days before admixture was developed to control concrete absorption rates. Back then, acids used during masonry washing could degrade the stone, which was a scary proposition. However, washing the architectural stone on a finished structure is a vital step. 

before and after washing cast stone
Before and after washing

Practically speaking, cast stone will encounter a gauntlet of harsh, grimy enemies between the factory and the finished install, such as jobsite rust, jobsite dirt, dust, mud, clay, mortar smears, green vanadium, brown manganese, white efflorescence, white scum, oil and grease, lime runs, atmospheric dirt, and black carbon stains. These, coupled with the misperception that using little or no detergent in the wash has led to some pretty ugly masonry projects. 

Cast stone showing white efflorescence
Cast stone showing white efflorescence

At Marcstone, we set out to solve the problems and eliminate any worry about washing cast stone. Rather than trying to avoid the unavoidable jobsite grime, we anticipate it. We designed our stone to have half the average absorption rate the Cast Stone Institute recommends to ensure that the detergent’s cleaning power is focused on the surface rather than soaking in and burning the product.

We produce stone at a higher PSI than the Cast Stone Institute’s specification, which significantly minimizes any worry of product deterioration that you may experience with other manufacturers. We anticipate a robust, efficient, and worry-free masonry wash, and we finish our cast-stone with that in mind. When you complete your final job site wash, the stone is in perfect, optimal condition.

Properly washed, vibrant cast stone

So next time you use Marcstone, grab that detergent, mix it strong and wash the grime off and expose the natural beauty and perfection of your cast stone.


Marcstone’s cast stone is designed to receive a final masonry wash using a standard masonry wash product.

We recommend these three, in this order: 

  1. Prosoco Sure Klean® Custom Masonry Cleaner
  2. Prosoco Sure Klean® 101 Lime Solvent
  3. Prosoco Sure Klean® 600

101 Lime and Custom Masonry Cleaner leave no white residue. Sure Klean 600, which is usually easier to find at major hardware chains, can leave a white haze, especially on darker colors, however with a little extra effort that can be removed with a more thorough rinse along with a light brush.

Prosoco® Sure Klean® Custom Masonry Cleaner

Prosoco® Sure Klean® 101 Lime Solvent

Prosoco® Sure Klean® 600



  1. Always pre-wet the surface with clean water, working from the bottom to the top. On vertical surfaces, keep the lower areas wet to avoid streaks.
  2. Apply the prediluted cleaner directly to the surface from the bottom up using a masonry brush or low-pressure spray.
  3. Leave cleaner for 2–5 minutes. Do not let the cleaner dry into the surface. If the surface begins to dry, reapply the cleaner.
  4. Reapply cleaner and remove any heavy buildup of excess mortar using a wooden scraper or piece of brick. Take care not to harm the masonry surface.
  5. Working from the bottom to the top, rinse thoroughly with fresh water. If pressure rinsing equipment is not available, then brush the surface while rinsing.
  6. Reapply as needed following steps 1–5.


As a final protectant where salt is more prevalent, Marcstone recommends sealing with a topical masonry sealer such as Prosoco Sure Klean® Weather Seal Natural Stone Treatment WB Plus or similar.

Prosoco® Sure Klean® Weather Seal Natural Stone Treatment

If you have any additional questions or concerns regarding how to wash or care for your cast stone, please reach out to use at 651-437-7972 or email

Printable Version