SEALERS

The history of sealing stone to preserve it goes back thousands of years. Tung oil which is extracted from the seeds of the tung tree has been used as a waterproofer for centuries in China and Japan. It has been recorded that tung oil was use to seal the Great Wall of China.
Today however, there is much confusion among homeowners, interior designers, architects and contractors about the many different products and treatments available on the market for stone and masonry surfaces, and all the different trade terms associated with them.
A MATTER OF DEFINITION 
The terms “sealer”, “impregnator” and “water/oil proofing”, “water/oil repellent” are often used interchangeably; in fact, they have technically different meanings from each other and this is where some of the confusion and unrealistic expectations originates.
Sealers : Conventionally these are “film forming surface coatings.”

Impregnators : These contain chemical and mineral agents that are absorbed into the pore/capillary structure of the stone or masonry materials that will modify certain physical properties.

Water/Stain/Oil Proofing : “Proofing” implies the application of a protective film forming coating or total pore closing agents that prevents the passage of water or vapor into or through  the stone or masonry material. These are “non-breathable” treatments.

Repellents : These are formulations of chemical and mineral agents that are absorbed into the micro-pore structure, modifying their size thus restricting the natural migration of moisture or oil into the stone. These are “breathable” treatments.
When you see or hear the terms sealers, sealants, impregnators or repellents used they generally refer to one other.

STONE TREATMENTS
Stone treatments have been divided into two major groups…

 Impregnators : These are penetrating subsurface treatments.

Coatings : They are surface film forming applications.

                                                            COATINGS                               IMPREGNATOR

Both groups contain breathable and non-breathable treatments. This is an important factor when considering any treatment for stone and masonry surfaces.

There are a number of categories associated with impregnating treatments…

Water Repellents / Hydrophobic : These are products that repel water, water based  solution and staining substances such as coffee, tea,sodas, liquefied soil, etc.

Oil Repellents / Oleophopic : They are formulated to repel oil based substances.

Water soil and oil staining substances                                               The surface becomes actively water,

combine to penetrate the pores and                                                  oil and stain repellent.
buildup in them.

Densifiers : These are agents that when applied to soft,  moderate to highly porous stones will make them harder. This is a good treatment for some varieties of stone used in heavy pedestrian traffic areas. They will also increase scratch resistance.

Consolidation Treatments : These are treatments for stabilizing and restoring the structural integrity of deteriorating stone and masonry materials due to the weathering processes and natural aging by replacing the lost mineral binders that cement the stone and masonry material together.

Color Enhancers : These products are formulated to impart and highlight the natural colors of unpolished, textured and faded stone and masonry materials. Some of the above products will also act as color enhancers on some materials as well.

Stain Proofing Agents : In certain situations some stones can be made to be stain proof in non-high risk installations…vanities, counters, furniture and off-grade interior flooring.

Many of the products in these categories are formulated in both water-based or solvent-based solutions, and both have their pros and cons. These can be determined when considering the material and situations (interior, exterior, etc.) of the application.

MOISTURE VAPOR TRANSMISSION 
You probably have heard by now that stone has to “breath”, and that this is some how related to the stone being porous.  Well, how does stone actually breath, and why is it so important?

Related to stones porosity is its permeability. This is the extent to which the pores and capillary structures are interconnected throughout the stone. These networks, their size, structure and orientation affect the degree which moisture vapors can migrate from the substrate by capillary action through the stone.

A particular variety of stone may be highly permeable (a well defined interconnected network of pores), although its porosity is low (a low percentage of voids).

So these two physical properties together result in a natural breathing as it were of stone.
Moisture is present in the ground and migrating. It can be wicked into a cement foundation by capillary action, this process of migration through a foundation and the stone is call moisture vapor transmission (MVT). If this natural vapor transmission (breathing) is not allow to take place this moisture becomes trapped and can cause a series of chemical and mineralogical changes to take place in the stone that will result in stone decay. The decay may take the form of spalling, pitting, flaking, or a lose of veining minerals, leaving pits or recessed veins. If the stone contains moisture sensitive matter or minerals these may
cause discolorations in the stone.

This is why it is so important that stone needs to breath!

SELECTING THE PROPER TREATMENT

There are a number of factors that need to be considered in order to select the proper treatment for the stone…

– The type of stone ( marble, granite, etc.)
– Pore / Capillary Structure…small or lager
– Density / Hardness
– Is the product formulated for a dense stone or for a stone with large pores?
– What is its solid content? Vapor transmission is reduced as solids are increased. This may or may not be desirable.
– Is the product compatible with the minerals of the stone. This will affect the products service life and may affect product performance.
– Environmental conditions…
Interior, exterior, wet areas (showers, pool / spa)
Climate conditions, general purpose areas, areas
where foods or oils will be present, etc.
– The finish of the stone…textured, honed or polished
– Will the product darken the stone?
– A solvent or water-based product
–   An impregnator (penetrating subsurface sealant) or a coating (film forming application)
– Is the treatment breathable or non-breathable, if it is breathable what is its vapor transmission rate (VTR). This is very important when

considering  consolidating and densification treatments. The higher the VTR in relation to water & oil repellents the better.
–  Service life of the treatment…6 mos.,1, 2, 5,10 yrs. This is how long the product will work before it needs to be reapplied.

– The products and methods used to maintain the stone after it is treated. Some products and methods will shorten the sealers service life.

Surface preparation and method of application are two other vital elements that will ensure the treatment will perform accordingly to its intended purpose and service life.

Over the past twenty years the results of research conducted by various organizations and product manufactures associated with the stone and masonry industries have indicated that due to the different types of mineral components associated with stone and man made masonry materials that various types of surfaces are more effectively treated with specific compounds.

There is no way to manufacture one type of compound and legitimately promote it as the best product for all types of stone and masonry surfaces.

When considering any type of stone treatment a careful evaluation needs to to done to ensure that the intended results can be achieved and are acceptable.

COMMON CONCERNS

Some common concerns that are frequently expressed when considering the use of a sealer…

Will it make the floor slippery? Or I’ve been told that sealing the stone will make it more slippery…This depends on the type of treatment that is being considered. If a “coating” is being considered this may be the case. However, there are coatings that meet or exceed the ADA requirements for slip resistance. If the treatment is a penetrating sealant they generally do not decrease the slip resistance of the stone or masonry material. If there is any question about the product you may be considering contact the company, they will be able to provide you with the information that you request.

Are sealers safe to use on my kitchen counters where foods will come in contact with the treated areas?…Simply stated, Yes. Penetrating repellents cure within the interior pores of the stone and after this curing process the food does not come in contact with it. Up until December 1995 the USDA required that sealers used in federally inspected meat and poultry plants be certified as safe to use, presenting no toxicological threats, and as of Dec. 1995 the USDA ended these certification requirements. These treatments pose no threat when used in food preparation areas.

It is highly recommended to consult with a qualified stone care professional when considering a stone treatment and what options may be available.