Cleaning process when using NMD 80 (new construction detergent) for the post construction cleaning of iron spot brick.
Thoroughly pre-wetting the surface is required. Attention should be paid to having water run down the wall at least 20 feet during the prewet phase. NMD 80 should be applied to an area no wider that the cleaner can easily rinse with the pressure washer in one long pass. This would generally be no wider than 12 feet. After the first application, but before scraping, the chemical rundown should be chased down the wall with water until no foam is apparent (rundown chasing occurs in the area below the cleaning space). Without rinsing the first application, apply a second application. The application person would again chase the chemical rundown with water before doing the final rinse. Thorough pre-wetting is only required on the first pass of the drop. Rinsing achieves the prewet on the rest of the drop.
The height of the cleaning space should be determined by the environmental conditions. Hot weather or direct sunlight would require a narrow (less tall) area. This is because you must chase the rundown and scrape before rinsing. This requires more operator time and generally a reduction in square feet on which the chemical is applied.
It is always wise with this type of brick to not start a drop if it cannot be completed on that day. In fact, experts say if a drop is started and certain dark mortars are used you must complete the full drop.
Mast climbing scaffolding proximity to the wall can make rinsing below a challenge. When cleaning on this type of equipment, the operator should create the maximum allowable space between the wall and deck. A hose “Y” should be placed close to the pressure washer with an auxiliary rinsing hose and nozzle attached with a second operator doing the rundown chasing. An alternative to this is attaching a soaker hose to the deck at the wall to create a constant source of water run down for the wall. This type of brick in a well-constructed wall should not have any excess water problems.
Be aware: If a chemical cleaner runs over the iron spot brick when dry, with mortar present, the glaze will disappear and leave a streaky iridescent or dull appearance. The use of OneRestore® sprayed on and rinsed off will restore the finish.