MOISTURE-STONE ENEMY
NUMBER ONE
Most of the problems associated with stone tile installation
can be traced to moisture or water intrusion of some kind. Many stains are
caused by the presents of water. Water is an essential ingredient for the
setting cleaning and restoration of stone but it can also be its number one
enemy.
What problems are associated with moisture and water. The following is a brief description of the
problems, there prevention and remedies:
Efflorescence
Efflorescence appears as a white powdery residue on the
surface of the stone. It is a common
condition on new stone installations or when the stone is exposed to a large
quantity of water, such as flooding.
This powder is a mineral salt from the setting bed. To remove efflorescence do not use water,
buff the stone with a clean polishing pad or #0000 steel wool pad. The stone will continue to effloresce until
it is completely dry. This drying
process can take several days to as long as one year.
Subflorescene
Subflorescene is what happens when the mineral salts migrate
and do not make it all the way to the surface. In the efflorescence condition
above, the slats are deposited on the surface of the stone. In subflorescene
the salts crystallize just below the surface, causing stress within the pores
of the stone. The result is a condition known as spalling which appears as pits
in the surface of the stone.
subflorescence is very common on green marbles and is very common on
almost all stone surfaces where de-icing salts are used.
Iron Staining
Many light colored stone contain naturally occurring
deposits of iron. Iron is a mineral found in stone and can occur randomly
throughout the stone. If iron is
present, it will begin to oxidize when exposed to water or other oxidizers such
as acids and household bleach. Stone can
remain for years without yellowing then
over time may slowly turn yellow and in severe causes may turn completely
brown. This oxidation process is
accelerated when the stone is saturated with water. This process of oxidation is similar to the
rusting of metal. If you expose a brand
new nail to water and air it will turn brown and rust. The same process is occurring with the iron in
the stone. If water and/ or air is eliminated the iron will not oxidize. This is the reason certain white marble
suddenly turn yellow. The process is
difficult to reverse and replacement of the stone may be necessary. The following stain removal technique has
proved successful in several cases.
Before testing this procedure it is important to first determine if iron
is the cause.
Testing for Iron:
1. Before assuming
the marble is yellowed due to iron be sure to attempt cleaning and stripping
with a good alkaline based stripper. If
these procedures fail then testing for iron will be necessary.
2. If a flood has
occurred or excessive water was used first check the water for iron. There are several inexpensive test kits
available that can be used to check the iron content in water. Check with your local plumbing supply store
or store carrying water softening supplies.
If any amount of iron is detected then it is possible iron has entered
the stone through the water supply. To
eliminate the iron there are chelating chemicals that can be added to the water
to prevent the iron from staining. This
is very important if the stone is cleaned with this water.
3. If the water
contains no iron and even if it does the stone should be checked for iron
content. Remove a small sample of the
stone and contact a testing lab and have
them analyzed it for total iron. If
there are spare tiles that have never been installed also have them tested for
total iron. If iron is present naturally
in this stone, it will probably be detected in the spare tile. If the results return with iron present
then the following procedure should be tested.
4. Check the stone
for moisture. A moisture meter is a
useful instrument that can be employed to check the stone for moisture. If the stone contains water, it is very
possible that iron is beginning to oxidize.
Removing Iron Staining:
1. Prepare a solution
of water and the following chemical: Sodium Hydro sulfite and Sodium
Metabisulfite. These chemicals are
available in a product called Iron-Out(TM) from your plumbing supply or home
center. Mix a solution in water and
apply to the effected area. Allow
solution to soak in and keep wet for several hours. Do not allow solution to
dry. After several hours pick up excess
solution with a wet vacuum and rinse throughly with water and a chelating agent
such as EDTA. Be prepared to repolish
any marble since these chemicals can cause etching.
2. If the above
procedure fails than prepare a poultice with diatomaceous earth and the Iron
Out(TM). Mix the poultice into a thick
paste and apply to a small area. Cover
the poultice with plastic and allow it to sit covered for 24 hours. After 24 hours remove the poultice paste and
rinse the area with water and a chelating agent. If the stain is removed, the entire surface
can be treated. If the stain still remains then replacement is the only
solution.
Before the above procedure can be performed, it is important
that the effected area be dry. If water
or moisture are still present, oxidation of iron may continue
The yellowing of stone is a common problem. New installations should be sealed with a
good quality penetrating sealer(impregnator) Which will help prevent oxidation
of the iron by eliminating moisture.
The above procedure has proven successful in some cases of
iron staining however if the following test does not produce the desired
results I would recommend replacement of the effected areas.
Warping
several type of thin stone tiles are very susceptible to
warping. Many of the green marbles and a few agglomerate marbles are notorious
for this warping condition. Many of an
installer have had the surprise to find that there tile installation has become
warped overnight. Why does this a happen and can it be prevented. Warping is caused by water. Green marble set
with any water based material will have a tendency to warp. The mechanism of why the tile warps is
somewhat a mystery. Some believe that
the water fills the pores of the stone and when the water evaporates the
orientation of the stones crystal change and cause it to warp. Whatever the reason, one thing is for sure,
green marble can warp when set with water based materials.
Cure: Once a green marble tile warps it is difficult to
repair. Attempts have been made to grind the tile flat , but this usually fails
since additional water is introduced during the grinding process. The green
simply warps again.
Prevention; The only way to prevent warping is to install it
properly with a non-water based material such as epoxy. Some installers have
also ben successful in sealing the back of the tile with epoxy and installing
it in a water based system(see July Stone & tile Report). Do not attempt to seal the back of the tile
with a silicone sealer. The silicone
acts as a water repellant and will cause the setting material to fail resulting
in a bond loss.
Erosion
Erosion is a condition found when stone is exposed to
constant amounts of water. This is especially true with marble that is used in
water fountains. While marble is a very
decorative material, it is one of the worst materials to use in or around
water. Marble is composed of calcium
carbonate. Calcium carbonate is a water soluble mineral. Quite simply this
means it will dissolve in water. Want proof, visit the Grand Canyon. Erosion can be recognized by a slow
deterioration of the stone surface. With polished stone the polish will be worn
off. In older installations, the stone may become very soft, brittle and in
extreme conditions, it will powder.
If any architects or designers are reading this article I
beg you no to use marble for water fountains.
If you do, plan on very high maintenance costs and plan on replacement
in about five to ten years if not sooner.
Stabilizing erosion:
If your faced with trying to stabilize a marble fountain
that is already deteriorated there are some treatment that can be applied that
will extend the life of the marble. These treatments are general called
consolidants and serve to replace the natural binders that are lost through
erosion. Consolidants can be tricky and quite often will cause discoloration of
the surface. Be sure to test the consolidant carefully before use.
Mineral crusts or Lime Putty
Mineral crusts or lime putty can be recognized by its white
crust like formation on stone surfaces. These crusts are often found on outdoor
stone stair, water fountains and other areas where stone is exposed to water.
The crusts are a deposit of hard mineral salts consisting of calcium,
magnesium. These minerals ordinate form the soil, setting bed or from the water
itself. These salts are similar to efflorescence in that they are a mineral.
They differ in that they form a hard crust that can be difficult to remove.
Crust Removal
there are only two ways to remove these mineral crusts.
Abrasion or chemical. The mineral salts
should be remove with an abrasive. I have found that a stiff non-ferrous wire
brush can work well. Brushes can also be
purchased that attach to an electric drill. Be careful and do not get to
aggressive. Avoid damaging the stone surface.
Quite often abrasion alone will not remove all salt
deposited. Strong Acidic chemicals will be required. These chemicals can be
purchased from most chemical companies that supply stone cleaning
products. Be careful when using these
products around calcium based stone since the acid can also damage the stone
itself.
Prevention.
The best prevention from mineral salts is to prevent
moisture form entering the stone. On
steps and fountains make sure all grout joints are caulked with a water proof
material. When installing steps outdoors make sure a water proofing barrier is
used. It is also a good idea to use a good stone impregnator on all surfaces to
prevent water from entering the stone.
Caution; Stone inpregnators will not waterproof stone. Do Not use them
where hydrostatic pressure is a concern.
TESTING FOR MOISTURE
To properly test for moisture a protimeter is necessary. A
protimeter is an instrument that reads moisture. The common protimeter has been
designed for use with wood, drywall and other similar substances. The protimeter contains two sharp probes that
are inserted into the wood or drywall to give a direct moisture reading in
percent. Unfortunilty you can not push
these probes into the stone, but the protimeter can give you important data oon
stone moisture. By placing the pins so
that the just touch the stone a relative reading can be obtained. For example, A reading of 0-6% is considerely
relativly dry. A reading between 7-20% is wet. A reading of of 20% is very wet. These readings only tell you that the stone
is wet, a little wet or dry. A direct percent reading can not be obtain with
these instruments, but can provide useful information.
Another simple technique for determining moisture in stone
is to take a piece of plastic about 12 inches square and place it on the suspected
stone. Tape all four edges and allow it to stay overnight or 12 hours. After 12 hours, if there is any moisture
present , you will see condensation collecting under the plastic.
TESTING FOR SALT
A protimeter can also be used to check for the presents of
soluble salts. The following procedure
will only tell you that salts are present. It will not tell you how much or
what type. But in many cases the simple presents of salts can indicate
potential spalling and/or pitting.
For this test you will need the following materials:
A rubber block
filter paper
distilled water
a protimeter
forceps
Any type of rubber will do as long as it is clean and does
not contain any salts. A piece of hard plastic can also be used. Filter paper can be purchased from a
scientific supply store and sometimes from the supplier who sells
protimeters. Distilled water can be
purchased from the grocery store.
The forceps are used to pick up the filter paper.
To check for soluble salts pick up a filter paper with the
forceps. DO NOT touch the filter paper with your fingers. The human skin
contains soluble salts which could be transferred to the paper giving a false
reading. Place the filter paper on the
rubber block. Add a drop of two of distilled water to the filter paper. Place
the probes of the protimeter to the filter paper and record the reading. Next, take a new filter paper and place it on
the stone to be tested. Add several drops of distilled water and take a
reading. Record the reading on a piece of paper.
If the reading obtained on the filter paper from the stone
is higher, then there are slats present. If it is the same or lower, salts are
absent. The protimeter works by reading
ionic changes. When salts are dissolved in water, the ionic changes are higher,
which gives a higher reading.
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