Manufactured Stone Maintenance: Keeping Stones Pristine

Words: Lynneice McNutt 

After a new structure is built, the last impression any stonemason intends to leave behind is messy and unprofessional work. However, when masonry is cleaned incorrectly, or worse, not cleaned at all, it can make a brand-new structure look old and worn, and hide serious defects that should be addressed sooner than later. 

Cleaning new masonry is a crucial step in the completion of a project: it serves to clear the faces of the units of any mortar that may have dripped or smeared onto them during installation, and makes it far easier to inspect the work for chips, cracks, or other forms of physical damage. Without cleaning the masonry, clients and laypeople alike will have a difficult time appreciating the skillful installation, and may focus instead on the smeared, muddy stones of the “new” walls. 

With hundreds, if not thousands, of chain restaurants and businesses operating worldwide with the express intention of achieving uniformity across their image or brand, some buildings are expected to look identical whether they are in humid Miami, Florida or frigid Anchorage, Alaska. To this end, manufactured stone is a strong material that provides the aesthetic consistency many of these companies’ desire. Manufactured stone is often colored artificially, so cleaning after installation can be a slightly different process than that of brick or natural stone. 

Know Your Stone 

Manufactured stone goes by several names: veneer stone, faux stone, manufactured veneer, and more, but its purpose remains the same. Natural stone has been used for centuries to provide strength and visual appeal to built structures. Over time, people have developed cities, villages and the general landscape to the extent that large deposits of natural stone are scarce and no longer a stone’s throw from building sites. Natural stone, while beautiful, is heavy. Transporting these materials can take notably longer and can cost much more than shipping in their lighter, more affordable counterparts. 

Manufactured stone can be made in a variety of ways, each of which contributes to the final look and strength of the stone. Generally, manufactured stones are made of a concrete mix poured into a mold that is often cast from real stones to achieve a more natural appearance. The use of lightweight aggregates makes the stone much lighter than traditional brick or natural stone. It can be hand-painted after it has set for a hyper-realistic stone alternative, or dyes can be introduced while the mix is prepared so the inner composite material more closely resembles the painted exterior. 

Modern machinery makes slicing manufactured stone into thin veneers quick work. The slivers of stone are generally less resilient than natural stone, so even if they are impregnated with pigment throughout, they run a higher risk of damage which could reveal the cementitious components beneath the face. 

The fragility and pigmentation of stone veneers means they may need to be replaced over time, as their color fades and they suffer cosmetic wear. While manufactured stone may be a more cost-effective solution initially, it will rack up additional costs in repairs and potentially replacement as time goes on. 

Maintenance and Cleaning Manufactured Stone 

The seemingly simple, but crucial first rule of cleaning manufactured stone is: follow instructions at all times, including during installation, during cleaning, and for maintenance of the material its lifetime. Different substrates have different compositions, and who better than the manufacturer to provide detailed instructions on how best to maintain a product? Some stonemasons install veneers top down so that falling mortar is less likely to sully the face of installed units below. Either way, following all instructions to a T will ensure cleanup is more streamlined. 

This extends to the use of chemicals to clean stones as well. Many companies are dedicating significant time, money, and energy into developing cleaning agents that can handle a variety of surfaces. This means there are plenty of options when it is time to select a cleanser, and extra care should be taken to ensure the right tool is selected for the job. Knowing whether the stone is integrally pigmented or finished with a colored Portland cement on the surface will inform the decision-making process, since some cleaning agents can be too aggressive for some veneers. 

The frequency of cleaning depends on the job. New constructions and restorations will require cleaning within three to seven days of completion to prevent mortar from drying on the surface of the units. For general maintenance there is no hard and fast rule; for some, every month the façades of their building need to be gleaming like new. Universities may invest more time into maintaining appearances this way. For others, cleaning once a year to every few years may suffice, and the masonry units’ ability to withstand the elements and time are important factors as well. 

The Right Tools for the Job 

Jayson Kellos is a Regional Technical Sales Manager for Hohmann & Barnard, Inc., and with eighteen years of experience as a commercial mason under his belt, he has learned the ins and outs of laundering manufactured stone. He recommends before all else, testing the cleanser on the stone. Taking a piece of the material, preferably an extra that has not been installed, and following the instructions for the cleanser of choice to test for colorfastness is critical. By testing on the installed veneer itself, there is a possibility the cleaner could strip the color, blast the texture away, or etch into the face while rinsing. 

When testing at the extreme end, like with undiluted cleaning solution, it can be determined if the stone is resilient enough to handle the cleanser in its strongest form (or in a worst-case-scenario). Take special care in the tools used to apply and rinse the detergents. Kellos recommends Diedrich’s Green Clean 250, a cleaner advertised as a safer alternative to muriatic & hydrochloric acids with an extended dwell time of five to ten minutes to permit use of safer concentrations. Even though it is advertised as safer, instructions should still be closely followed to protect the stone. “Educate yourself on the product you are using, as well as the material being cleaned,” Kellos says. “Never let the cleaner dry on the wall, and always use proper diluting ratios.” 

Cleansers like Diedrich’s Green Clean 250 can be applied with a soft, natural brush and rinsed using low to no pressure. Kellos recommends, “when washing, a wide 20- to 40-degree spray tip should be used. This will give the user a productive spray, while preventing the face from being carved or etched by the spray pattern.” In addition, keeping the stone clear of mortar during installation will make the final cleaning easier. For mortar that lands on the masonry units, avoid wiping it away, as it will smear and become difficult to remove later. Allowing it to dry slightly will make it easy to remove using a wooden scraper. 

Some products, like EaCo Chem’s NMD80 and SOS-50, are considered aggressive cleansing agents due to how easily they can strip color from stone veneers if they are not used correctly. Lynn Penden, President of EaCo Chem, says “anyone can use our process, but it is important like with any new tool to understand how to use it appropriately.” He recounts the story of a contractor who, against clear instruction provided with the cleanser, brush the cleanser onto the substrate (where it is marked as a ‘no brush zone’) and followed it by using high pressure to rinse (when instructions dictate to use the application tool with low pressure). The color bled from the manufactured stone and the contractor blamed it on the product. However, when EaCo Chem’s products were used on the same type of veneer and applied according to the manufacturer’s directions, the stone was completely colorfast. 

“From our standpoint,” Penden says, “the misconception that comes along with the cleaning process [for manufactured stone] is if I want to scrub, it’s alright. If I want to rinse with high pressure all the time, it’s all right. It is not alright.” Different tools and chemicals react very differently, so things like dilution, pressure and even air/weather conditions should be taken into consideration before applying a chemical to the finished installation. Testing the cleanser in similar conditions to when it will be used is crucial. 

Penden explains that the chemistry of the product can be sensitive to things like changes in humidity or temperature, but at the same time, the beauty of chemistry is in its versatility. EaCo Chem’s Ultimate Safe Urban High-Rise Restoration System is designed with the surrounding environment in mind; some cleansers can be used at extremely high dilutions, like 30:1 or even 50:1, and when the cleanser was applied with a pressure washer using a five gallon/minute output, it underwent neutralization as it came into contact with the alkaline surface of the structure. When the rinse water flew over the surrounding area, there was no risk of harm to the redwoods, people, or wildlife. 

Even with perfect chemistry and an experienced contractor at the helm, one cannot understate the importance of testing. As Penden puts it, “the critical thing is that [you perform] one test to determine whether it’s no scrub, no high pressure, or [if] you can scrub and [use] high pressure, and you go ahead to whichever way is appropriate. So just take a piece that’s not on the wall and determine what’s appropriate, that’s the smartest thing you can do to guarantee success.” 

Keys to Successful Cleaning 

Testing is a vital part of the cleaning process when determining what approach will leave manufactured stone clean and unscathed. There are other tips to keep in mind when tackling the laundering of a new construction or renovation: 

1. Pre-wet the area: masonry is notoriously porous, so if the joints are dry when the cleaning chemical is applied, expect it to be soaked straight into the wall where the chemical can erode the masonry. Think of it this way, if a sponge is already soaked, it cannot absorb anything further. 

2. Pay attention to the mortar: Some say that mortar joints do not require intense scrubbing as the intent of cleaning is the remove excess mortar that may have smeared onto the masonry units during or after installation. Other experts, like Hohmann and Barnard’s director of technical services, Jeremy Douglas, emphasize that dyed mortar joints are as liable to have their color stripped if the cleaning process and chemicals used can do this in the stone itself. 

3. Use the right equipment: There are a variety of pressure washers on the market today that boast power, heat and other features to get walls clean. Remember that manufactured stone may not be able to stand up to the power of these washers. See what the cleanser calls for and if it needs a proprietary applicator or system. 

Brick and natural stone are strong, versatile, and aesthetically pleasing options for all sorts of projects. But, in cases where a lighter option is needed or the budget is a little tighter, manufactured stone can be a great solution. To keep it looking like new will require care, but the sight of the veneers gleaming in the end will make it all worth the effort.