Our Research‎ > ‎

Architectural Stone


This is a common question for property owners, managers, contractors and suppliers all over the world. Many factors can cause stone stains. Most stains are due to insufficient maintenance, inappropriate water-repellants used to seal precast, caulking leaching onto adjacent stone materials, and careless window cleaning practices.

If the precast on your building was sealed but is still leaching minerals onto glass surfaces, click here.


There are many different types of architectural stone material, all of which have different characteristics which need to be understood before determining the best means of maintenance or restoration. 

It is important to select a product that will allow you to achieve the desired results when cleaning stone materials. Each of Presto’s products has a suitability chart, within its product data sheet, that shows the differences in stone types, and their compatibility with the individual product.

Presto’s Five Stone Classifications:

  • Architectural Materials: Comprised of multiple ingredients that are mixed, and cured, to create the stone material; Examples: concrete, precast, cast in stone, terrazzo, stucco
  • Siliceous Natural Stone: Mostly comprised of silica and/or silicates that have naturally crystallized in order to form the stone material; Examples: granite, quartz, slate, sandstone
  • Calcareous Natural Stone: Mostly comprised of calcium carbonate that has naturally formed to create the stone; require special cleaners and sealers, as this type of stone is easily damaged using acidic products; Examples: limestone, marble, travertine
  • Masonry & Grout: Free-standing manufactured stone or siliceous natural stone units that are held together by mortar; Examples: brick, block, slate
  • Tile & Grout: Tiles are cemented to a surface, with grout filling the spaces between each tile.


For years people have believed that more pressure was better for cleaning stone. Each time a stone surface is washed using high pressure, a layer of the stone material is removed. This is especially detrimental to precast and concrete materials that have a thin top layer on the material that covers the coarse aggregate within the stone. In many cases, using lower pressure in combination with the proper products will safely and effectively clean the stone without altering the surface of the material.

Stone Restoration Before After Photos
View Before & After Photos


Many times damage is caused by incorrectly choosing or incorrectly using a product. Products should always be utilized in the manner outlined on the label, and in the product data sheet.

When you are cleaning stone, damage is normally caused in the last few applications of the chemical, especially when trying to get the material just a little bit cleaner. Sometimes stains are so deeply imbedded into the material, that they can never be 100% removed. Knowing when to stop applying a product can save the stone from damage. 

It is important to realize that when using an acidic product, like Presto’s Stone Restore® HD, a very thin layer of the stone material is dissolved in order to remove stains that have permanently adhered to the stone material. Each application of this product will dissolve another layer of the stone as well as the stain that is imbedded into it.

Many times adjacent surfaces are damaged due to performing restoration or cleaning services without preventing over spray from residing on unintended areas. It is very important to protect adjacent building surfaces, or include the restoration of adjacent surfaces when using chemical processes.

Overspray is a common occurrence during the application of stone sealer. Many sealers are very difficult to remove from surrounding metal and glass surfaces, often despite “glass friendly” claims made by the manufacturer. Products are often determined to be "glass friendly" when tested in a laboratory environment; since it is easily removed after application to perfectly clean glass, or removed without first baking in the sun. 

In real-world application, after washing a building’s stone, there is stone sediment on the glass and frames. The stone sealer overspray reacts with the sediment forming a sticky, oily residue that is baked on by the sun, and becomes difficult to remove. In this situation, Presto’s EnviRestore® products will often effectively remove these stains from glass, metal and polished stone surfaces, without damaging the substrate.


Imagine taking a shower and not using soap, or washing the dishes with oil instead of dishwashing detergent! This may alarm you as much as it does us when we see contractors using mediocre or incorrect products to perform building maintenance services. For example, many times pressure washing is performed on concrete without using chemical cleaners, and without the application of a sealer after the pressure washing is finished. 

Properly selected cleaners loosen many different types of soils that adhere to concrete similar to the way dishwashing detergent carries oil away from dirty pots and pans. De-greasers help to loosen oils and grease, bleaching agents work to remove mold and algae, acids work to remove stains such as rust and efflorescence. In conclusion, choosing the right product is essential to the overall outcome of the project. 

It’s important to choose the most suitable product for: 1) The stone material to be cleaned, and 2) The stain that is to be removed. 

Many times the wrong product is selected due to the consideration of only one of these factors, and the desired results are not achieved. Presto has developed a product to tackle every stain commonly found on stone surfaces. 

Below are links to our suitability charts for cleaning many different types of stone materials and stains. These charts will guide you to the product best-suited for your specific cleaning need.
When the correct products are used, stone is restored to a state similar to that of its original manufactured condition. When a test area is performed with our products versus our competitors’ products, it is visibly clear that Presto's products provide the most impressive results on the market.


Sealers should be used after the stone cleaning process to close up the pores of the concrete or stone, in order to prevent the penetration of water and oil which act together to stain the stone again. Sealers will help keep stone cleaner for longer and help to protect from water damage, therefore, prolonging the life of the material.

When restoring stone, it is always important to identify the cause of the stain, and prevent the stain from reoccurring at the source. After restoration, and curtailing the source of staining (if possible), it is important to protect the surface in order to help prevent future restoration.
  • To prevent the need for frequent pressure washing - Sealed stone stays cleaner for longer, and resists staining and discoloration.
  • To guard adjacent materials from mineral leaching - Excess minerals leach from precast onto architectural glass, metal, and other materials where mineral stains are form relatively quickly. Sealing your precast keeps adjacent windows looking cleaner for longer.
  • To prevent oil, water, and stain penetration - Many types of soils can adhere to stone surfaces: vehicle exhaust, tree sap, fluid from leaking vehicles, and many other environmental contaminates.
  • To prevent mold and mildew - Sealing stone material prevents the penetration of water. Without water, green and black algae stains are unable to develop as they normally would.
  • To avoid water damage - If water is allowed to penetrate your precast, it starts to erode the bond that holds the stone together. This is especially damaging during winter months as water freezes and expands, compromising the strength and bond of the manufactured stone composition. This causes cracks, and even separation of material components, and is extremely expensive to repair. In situations with precast panels, water damage normally only occurs at the surface level, therefore requiring a product designed for superior surface protection.
  • To protect your steel components - If water is allowed to penetrate your concrete, and is exposed to steel components that hold your building together, they will start to rust. This can cause structural damage and material staining.


There are many different types of water repellant materials available today. Silanes, siloxanes, silicones, acrylics, waxes, epoxies, siliconates and fluoropolymers; just to name a few. In addition, many of these materials can be mixed together to create a totally new material for use on various surfaces. It is important to not only chose the correct product for the required application, but to also ensure that the product is applied properly. 

Presto is the first company in the world to create an exclusive line of products to specifically combat the problems involved with precast leaching onto, and staining, adjacent glass surfaces. 

Below are links to our suitability charts for cleaning and sealing many different types of stone materials. These charts will guide you to the product best-suited for your specific stone restoration or stone sealant need.



Silane is an oily liquid that is designed to react with the silica in stone. Upon application, silane forms a resinous gel that fills in the cracks and crevices in the stone, blocking water from penetrating into the stone. Over time this resinous gel hydrates, and creates a harder, glass-like material that becomes part of the stone itself. 

Silane is one of the smallest of all water-repellant molecules, enabling it to penetrate deep within the substrate, and protect structural materials. While silane water repellants are suitable for many situations, they are undesirable for use on high-rise buildings with flush mount window systems because this material can actually help to create unsightly stains. It’s important to select a company that creates products with all of your building surfaces in mind.

The water repellant most commonly used today to seal architectural stone consists of 40% solid content silane. We have seen countless buildings that have sealed their precast using 40% silane only to have the material break down and produce excessive leaching in as few as two years from the date of the application. In our experience 40% silane is one of the least effective product options available for vertical precast surfaces, especially when flush-mounted windows are present.

It’s also important to understand the disadvantages behind using silane so that you will have all the information that you need in order to make the smartest decision possible when selecting a sealer for your building’s stone surfaces:
  • Silane is oily, UV- and heat-sensitive - When the atmospheric elements meet silane-protected surfaces, their molecules degrade and leach out of the building materials, decreasing the concentration of protection on the surface. Since the molecules deteriorate so quickly, product manufacturers use a higher strength of silane than needed in order to compensate for the loss, which is why a 40% concentration is commonly used.
  • Products made with silane react with the silica in stone to create a resinous-like material - This in turn creates the water-repellant effect. With such a high concentration of silane molecules, much of the silane material does not come into contact with the silica within the stone, and therefore cannot react and become the resinous, repellant material. The remaining product leaves behind an oily residue and leaches onto surfaces below.
  • Stone is a breathable, porous material - Stone surfaces that are protected by silane are still breathable and allow the molecules to exit the stone material freely. After the stone is heated by the sun and cooled again, it breaths allowing moisture and silane oils that have not bonded with the stone’s silica to leach out and reside on other building surfaces. There it absorbs dry, airborne materials like dust and dirt that are also made of silica. This triggers the reaction that causes the silane to turn into a resinous, repellant material on unintended surrounding surfaces. This is a major cause of hard-water stains, the worst type of stain to have on glass. Additionally, minerals in tap water, window washing detergents and other environmental contamination are fused into this mixture and baked onto the building surfaces as well.
  • Surfaces sealed with silane materials offer poor surface protection - Water is allowed to penetrate the surface of the “protected” stone immediately, allowing water to come in contact with the stone material. Under the surface, the stone is protected; however on a high-rise building, it is more important to consider the protection – and appearance – of the outermost layer of the stone material.
  • Silane is organic and breaks down rapidly, attracting pollutants that eventually wash down the building - This waste collects around the base of the building where it resides in high concentrations, often near public seating and eating areas.
  • When organic silica materials degrade, they disperse into the soil and ultimately the water supply - Because millions of gallons of silane based products are running down buildings each year, the silica content of our water supply increases, due to the fact that the water system is not designed to filter out minerals. While this has not been proved to be hazardous to our health, this high mineral content water causes other expensive problems such as stains on glass, buildup in cooling systems and spotting in car wash applications.

Silane is hardly a “Green” solution to building maintenance!

Silicone and other new fluoropolymer materials, react with moisture in the air, and harden without requiring contact with silica. These more suitable materials will evenly cover the surface of the stone, and cure in place, remaining on the surface, and protecting it for up to 20 years. These products are extremely UV-resistant, and repel water as well as many types of environmental staining, including oil. These materials are approved for spray applications, and it is easy to see why they are considered to be the “greenest” option available today.


It is critical to select the right combination of products to protect the environment, and maintain the exterior beauty of your building. Presto has designed products to work synergistically – not against one another.

Follow Presto’s three-step process: Restore, Protect and Maintain.


Stone Restore® CT (Citrus Technology): Powerful, environmentally friendly, citrus-based concrete cleaner clears the toughest oil stains as found in parking decks

Stone Restore® NC (Neutral Duty):
A medium duty restoration cleaner specifically developed for use on chemically sensitive architectural stone surfaces such as limestone, marble and travertine

Stone Restore® PS (Polished Stone):
A mildly abrasive restorative cream that removes waterproofing overspray, lime and calcium stains, soap scum and other tarnishes from polished stone surfaces

Stone Restore® CB2 (Chlorine Bleach): Double-strength chlorine bleach contains builders and surfactants that effectively fight oil stains and microorganisms such as green or black algae and mold allowing them to be easily removed using water

Stone Restore® A+ (Alkaline Technology): Removes stubborn environmental staining as well as oil and grease stains from most types of stone

Stone Restore® HD (Heavy Duty): Acid-based cleaner for all types of stone that effectively removes a wide variety of stains, including mineral-based stains such as efflorescence and rust; special precautions are required when using this product to clean limestone, marble or travertine



Leach Stop®: Clear, penetrating treatment designed to protect GFRC, precast and concrete surfaces from mineral leaching, stain development, water penetration and water erosion

Protect-A-Stone®: Clear, penetrating sealer that utilizes proprietary UV-resistant fluorochemistry to create a barrier against oil, water and stains without altering the stone’s appearance; protection can be renewed with ReJuviClean® stone preservation product

Stone Guardian®: Clear, deep-penetrating surface protection that utilizes proprietary UV-resistant fluorochemistry for superior water, oil and stain resistance; protection can be renewed with ReJuviClean® stone preservation product

ReJuviSeal®: Clear, penetrating sealer that utilizes proprietary UV-resistant fluorochemistry to create a barrier against oil, water and stains without altering the stone’s appearance; protection can be renewed with ReJuviClean® stone preservation product

Presto product applied to a 
stone surface. The protected 
stone forces water to bead up and 
run off the surface.


After one month of oil and 
transmission fluid on a stone surface protected with Protect-A-Stone. Coating allows for beading and not penetration of outside elements.



ReJuviClean®: Light-duty cleaner that renews three oil, water and stain repellants in Presto’s product line (Protect-A-Stone, Stone Guardian, ReJuviSeal)

— Capturing the water in cleaning processes is essential to protect our environment. Never allow any cleaners, oils or other products - even biodegradable products - to wash down drains. Building owners, property managers, and service contractors are subject to large penalties by the EPA if caught allowing degreasers or oil to run into drains. Presto supports the EPA in their efforts to prosecute offenders.

Click here to view all of Presto’s Stone products

Judah Clark,
Jan 7, 2010, 5:30 PM
Judah Clark,
Jan 7, 2010, 6:49 PM
Judah Clark,
Jan 7, 2010, 6:49 PM
Judah Clark,
Jan 7, 2010, 5:40 PM
Judah Clark,
Jan 7, 2010, 5:40 PM