STONE TREATMENTS
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.
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.
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.
