Spring 2014 - Our 33rd year in business.
The economy is starting to show some signs of life, especially in the service sector where most of our market resides.
Capital investment is way down and a lot of cash is on the sidelines just waiting for some assurance that the economy is really moving forward again. We have seen some
improvement this season and I hope it portends a positive trend upward.
Good service and an aggrissive sales program will get us all through this major bump in the road.
Please let me know if Hydroclean can assist anyone in any way.
Tom Rudder
President
Procedures for the Cleaning of Interior Stone.
Our industry is generally involved with the cleaning and
restoration of building exteriors. One hears very little about the cleaning
of interior substrates. This article is dedicated to the cleaning of the
limestone, marble, granite, brick or terra cotta found in building
interiors. Architects have always appreciated the color and architectural
accents that interior stone can bring to building lobbies and other
impression rooms within the building. Stone is used on floors, baseboards,
wainscots, or on entire walls and ceilings. Although interior substrates do
not have to endure the ravages that weather imposes on exterior stone, they
do have their own contaminants that can compromise their beauty.
Interior
contaminants are mostly carbon based and come from misplaced hands, shoes
and hair. Soot from old oil or coal fired heating systems is another
carbon-based contaminant that gets deposited on interior stone. It was not
that long ago that people were allowed to smoke within a building and thus
more carbon.
Carbon-based
interior contaminants are generally easy to remove and will react best with
a mild alkaline cleaner. If a given cleaner is capable of removing the dirt
and is mild enough, the cleaning can be accomplished with a one step
process. If a stronger alkaline is required, then the cleaning process will
require a second step that will consist of a mild acidic after wash. The
acid after wash will perform two functions. The first is to remove any
inorganic material (metals) that may be on the surface and the second is to
neutralize any residual alkalinity from the first step. For polished stone
use only mild cleaners. The polished surface limits the porosity of the
stone so most of the contaminants stay on the surface and are easily
removed. Exercise extreme caution using the stronger cleaners on surfaces
that have been honed to a polished finish. The stronger cleaners may
compromise the finished surface.
The
best results for interior cleaning are achieved using the following
process. First perform some test cleaning areas to determine the proper
cleaning product and the appropriate dilution ratio of the product. Give
the sample areas plenty of time to thoroughly dry and then observe the
results. Make sure, through testing, that the end result is what is desired
before commencing on the project. The manufacturer of the cleaning products
can have their representative assist the contractor/architect/owner in
determining the correct product and its dilution. After applying the
cleaning product and waiting the proper dwell time, the stone must be
rinsed. In all cleaning projects the rinse cycle is just as important as
the choice of a cleaning product. For interior cleaning the best results
are achieved by using water pressurized through an airless sprayer that is
capable of 1500 psi and a gallon per
minute. The sprayer's gun will deliver the spray in a 15 to 25 degree fan
making the rinse even and controllable. The effluent from the rinse process
can be easily collected with one or more wet vacuum cleaners. The entire
process is an efficient, controlled closed loop system.
The
pressurized water rinse is necessary to reach into the pores of the stone
and to remove all traces of the cleaner and the contaminants.
Workmen
who have experience using the cleaning system outlined above will have
little trouble with the protection of contiguous areas. Normal common sense
applies. If there is a rug at the base of the wall that is being cleaned,
it must be removed or at least rolled back. The floor or wall electrical
outlets must be covered. Any artwork or signage must be removed and any
wooden surface must either be protected or removed. The wet vacuum cleaner described
above will easily be able to control the effluent.
It is always best for any
cleaning work to be performed after normal working hours when the workers
will have the building to themselves. Although interior cleaning products
and the application and rinse process is generally non-hazardous, it is
always preferable to keep the building's occupants away from the work
areas. Even a mild smelling cleaner can cause some people to have
unrealistic concerns and to complain.
The exterior
of a building will dry fairly quickly after cleaning. It has the wind and
the sun helping the moisture within the stone to evaporate. Not so with
interior stone. The air pressure of the ambient air within the building is
relatively high and constant, so it will take some time for the residue of
the rinse water to evaporate into the building's atmosphere. In the
meantime, due to the varying porosity of the stone, it may dry unevenly.
The areas around the substrate's joints will hold more moisture and might,
at first, look darker than the surrounding stone. The impression can be
that it was incompletely cleaned and the temptation will be to re-clean the
wall. But it is best to just leave it alone and give the surface the time
it needs to dry. Depending on the humidity, the season and the building's
air handling system, it may take as long as three months for interior stone
to completely dry.
The
results of a properly managed interior cleaning program are generally very
satisfactory. The advice to follow, as on all building cleaning projects,
is to use experienced contractors and cleaning products from manufacturers
who have a long demonstrated history of successfully cleaning stone.
Thomas H Rudder
President
Philosophy of chemical formulation
Manufacturers
of restoration cleaning products as well as restoration contractors have
had to deal with much misunderstanding over the design and safety of
chemical cleaning products for masonry. Even with the array of
sophisticated building cleaning products on the market today, we are
unfortunately still dealing with the unsavory reputation that the building
cleaning industry earned during the 1950's and 1960's when building
exteriors were cleaned using raw hydrofluoric acid and the strong alkalis
that were, and still are, used as floor strippers. Many beautiful building
exteriors were compromised during that era. The industry has come a long
way, but we are still fighting the connotation that chemical cleaning is
unsafe for historic substrates. I would like to attempt to review the
process of how a product for cleaning stone is designed and formulated. The
purpose is not to offer a definitive course in chemistry, but to give the
architect, contractor, historical consultant and building owner a general
understanding of the thought process that a modern manufacturer uses to
develop safe, effective cleaning systems for masonry substrates.
The
first step in designing a cleaning product is to identify the contaminants
that we are trying to remove. In large metropolitan areas masonry buildings
have some carbon build-up, various salts, silicates and oxides from the
incomplete combustion of fossil fuels. The over simplified chemistry of
fire is that the exhaust (smoke) is acidic and the ash is alkaline. So when
the exhaust from power plants and automobiles is deposited on buildings we
have, in addition to the carbon contamination, sulfur oxides from the
incomplete combustion of high sulfur fuel oils and nitrogen di-oxides and
tri-oxides from the incomplete combustion of gasoline. Reintroduce moisture
in the form of humidity or rain and these oxides form sulfuric acid and
nitric acid, both of which are extremely detrimental to masonry substrates.
Other exterior contaminants include various metals such as magnesium, iron,
copper, aluminum and other metals and their salts that are inherent to our
industrialized economy.
Most
manufacturers attack the contaminants found on brick, granite, sandstone,
limestone or marble building exteriors with water-based cleaners that either
have an acidic or an alkaline pH. The acid(s) or alkaline(s) in the
formulation perform various functions necessary to break the bond of the
predetermined soils from the stone. Wetting agents are added to the formula
to release the surface tension of water and thus allow the water based
cleaner to penetrate into all areas of the contamination. The job of
emulsifiers is to hold the contaminants in suspension until the rinse cycle
can be applied. Good emulsifiers will also help to insure that the product will
rinse well which will assure the removal of all traces of the
cleaner/contaminant effluent during the rinse cycle. Buffers are used as a
safety factor and their job is to retard the reaction of the acids or
alkalis. Even though some products necessarily use a percentage of acids or
alkalis in their formulations that are considered, by themselves, to be
very strong, the buffers serve to retard the reaction to the point that the
formulation is safe for use on masonry. Thickeners give the formula some body
and that allows the product to hold on vertical surfaces. Some products
have humectants that attract moisture to help the product stay wet until it
is time to rinse.
Brick, granite and sandstone
can generally be cleaned using a one step, single product process that can
remove both the organic (carbon) and inorganic (metals) contaminants from
the building. The rinse cycle, which is a separate but equal part of the
cleaning system, serves to both flush the product/contaminant effluent from
the stone and to neutralize the stone so that upon completion of the rinse
process the substrate is left evenly cleaned and with a neutral pH.
Limestone
and marble are comprised of the more sensitive calcium carbonate, so these
building substrates usually are cleaned with a two-step process. The first
step is to apply an alkaline cleaner that will loosen the organic (carbon)
based contaminants. After a dwell time the effluent is rinsed and then a
mild acidic product is applied and rinsed. The acidic product will perform two
functions. The first is to remove the inorganic contaminants (metals) and
the second function is to neutralize any residual alkalinity left from the
first step. It is important that any building be left with a neutral pH,
but as calcium carbonate buildings are basically alkaline to begin with, we
do not want to leave any excess alkalinity imbedded in the pores of the
stone. Calcium carbonate based substrates are extremely sensitive to harsh
cleaning methods, so great care must be taken when choosing acid or
alkaline constituents for their cleaning products.
Interior
contaminants are much less complicated to clean and generally consist only
of carbon-based soils such as hand sweat, cigarette smoke and soot from the
building's heating system. Generally all that is needed is a mild alkaline
cleaner that can emulsify the soils and then a thorough rinse using a
rinsing system designed for building interiors.
Some
building cleaning projects require the removal of paint. The buildings may
be totally coated with paint or there may just be some graffiti. Paint
removal requires a different type of chemistry that will be discussed in a
future article.
Manufacturers
of chemical cleaning products will provide detailed instructions on the
proper use of their products. These instructions must be followed exactly.
Depending on the individual formulation, the application of the product,
the dwell time and the rinse process may vary from manufacturer to
manufacturer. So for the best results, the contractor must pay close
attention to the outlined procedures. Each product is designed to safely
emulsify building contaminants and hold them in suspension until the rinse
cycle can be applied. The rinse cycle is just as important as the
application of the cleaner. Its function is to flush all traces of the
contaminant/cleaner effluent from the stone and to leave the stone
neutralized. The rinse cycle must be accomplished in a timely manner and
must be performed slowly and deliberately thus assuring a complete rinse of
the substrate.
The
rinse process must have a certain pressure and volume ratio to accomplish
the task of thoroughly rinsing the stone. The hitting force of water is
determined by both the volume of water and the pressure at which the water
is delivered to the surface of the stone. Any good cleaner is designed to
migrate into the stone in order to emulsify the interior soils as well as
the surface soils. Therefore the rinse cycle must have the power to flush
into the substrate to remove all traces of the contaminate/cleaner
effluent. Water hose or other ludicrously low pressure/volume combinations
will not adequately rinse a building unless the rinse process goes on and
on poring great volumes of water into the building. Most non-friable
building substrates can be safely cleaned using a pressure of 1500 to 1800
pounds per square inch (psi) and a volume of 4 to 5 gallons per minute
(gpm). The water/pressure rinse combination is delivered through a
high-pressure water gun with a 15 to 25 degree fan tip. This
pressure/volume will work with brick, granite and most sandstones. It will
also safely rinse most calcium carbonate based limestone and marbles. These
pressure/volume combinations have been successfully used for many years and
will not harm the substrate or any sound mortar. In addition to assuring a
complete flush of all traces of the cleaner, these pressure/volume
combinations play a vital role in assuring that the building is evenly
cleaned and that the rinse effluent is dilute enough to enter the City's
sanitary sewer system.
In the case where a substrate
is extremely friable, lower pressures may be necessary. It will be the
contractor's responsibility to be sure that the building has been
thoroughly rinsed. The contractor can test for any residual acidity or
alkalinity remaining in the building's substrate by using pH paper, which
should be on every building cleaning jobsite. The objective is to leave the
building's surface as close to a neutral pH as possible.
A
properly cleaned building will display a symmetry of evenly cleaned stone
that will showcase the natural color and hue of the masonry. The cleaning
will have been accomplished without altering the surface or the porosity of
the stone. Once completed, it will accurately represent the original
architect's atheistic design and intent.
Remember that cleaning a
building requires the adoption of a system that includes the choice of the
right cleaning product, the right pressure/volume rinse combination and the
right contractor who will perform the work. Compromising any of these three
elements could compromise the entire cleaning project. The best safety net
is for an owner/architect/building manager to insist on using experienced
product manufacturers and experienced contractors both of whom should have
a long demonstrated history of cleaning historic buildings.
Thomas H Rudder
President
|