Stain Removal

All stone is absorbent, some more so than others. This is due to the stones physical properties related to its porosity, permeability and absorption.

The staining of stone and masonry surfaces can prove be problematic for a variety of reasons. 

• Some spots that look as if they may be a stain are actually etches or a hazing
  or dulling of a highly polish surface. Marble, limestone and travertine are typical
  stones affected by these situations. These types of situations may also be a
  combination of a etch and a staining substance or a prolonged soiling of the etch
  causing it to appear as a stain.
• The minerals in stone have a definite chemical composition, because of this in some
  situations certain chemical reactions can take place between a part of the chemical
  composition and the staining substance producing a permanent stain to occur.
  Some plant fertilizers can cause permanent chemical reactions to occur.
• Some stones have moisture sensitive minerals and substances that can cause the stone
  to develop stains.
• The ingredients in some stain removal compounds can cause a slight irreversible
  bleaching effect to dark colored marbles and limestone's.
• Using the wrong chemical can carry the stain deeper into the stone or set the stain
  making it permanent.
• Old or deep-seated stains may not be fully removed leaving a slight shadow or they
  may not be removed at all.
• A hazing, dulling or etching of a polished finish may occur.
• The longer a stain remains it migrates deeper into the fabric of the stone and becomes
  more permanent.

Identifying the Stain

Stains have been classified in a few ways...Organic and inorganic, water-based, oil-based
and have been fitted into five categories...

• Organic : Food, fruits, coffee, tea, beverages, cosmetics and tobacco.
• Oil Base : Greasy foods, cooking oils, grease, tar, skin and hair oils.
• Inks / Dyes : Felt tip markers, pens, natural and synthetic dyes.
• Biological : Vegetation, mold, mildew, algae, fungus, etc.
• Metallic : Iron (rust), copper, bronze, etc.

It is important to try to properly identify the source of the stain for a couple of reasons.

• Different types of stains respond to different types of chemical agents and
  removal methods.
• If the wrong chemicals and methods are used they may spread the stain, and carry it
  deeper into the stone and permanently set it or create a whole new stain.

Sometimes the cause of the stain is unknown. If this is the case than ask yourself a few question and look around to see if the stain fits into one of the five categories, also color may provide a clue.

Color Clues to Stain Identification

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Stain Removal

In order to draw out the staining substance that has been absorbed into the stone an
absorbent material needs to be applied to the stained area. This process is referred to
as a poultice.

There are several premixed wet poultice products available, as well as powder poultices
that only require the addition of water to activate them. They are more convenient and
safer to use than formulating your own stain remover. These usually can be purchased
at a marble or tile store. I highly recommend that this type of product be part of your
stain removal kit so that when a staining situation does happen you can address it as soon
as possible. Make sure that the product you buy is compatible with the stone you
intend to use it on. Example...Some products will say that it is not to be used on some
types of stones, read the label thoroughly and do not just take the word of the
salesperson for granted.

Poultices are more effective when plastic is placed over them and taped down. This
prevents the poultice from drying out to quickly, allowing the chemical to work on the
stain. The poultice should remain covered approximately 24 hours, then the plastic
removed. If the poultice is not dry at this time it should be allowed to air dry so the
staining substance can be drawn into the poulticing material. When poultice is dry
remove using a wooden or plastic spatula and rinse well.

The stone may have a dark damp spot where the poultice was, this may take a day or so
to dry in order to determine if the poultice has worked or if another application is needed.
Some stains require a few treatments. A good rule of thumb is...If after two applications
the stain has not changed it may be permanent or it is not responding to chemical and at
this point I would recommend that you call a stone care professional.

It has been estimated that approximately 85% of the stains in stone and masonry materials
can be removed successfully and the remainder will either lighten to one degree or another,
or they are permanent.

Do not wipe a wet stain to pick up the solution, this may spread the stain. Use an absorbent
cloth or paper towels to blot it up.

The following is a general guideline for known stains. If in doubt call us at Cornerstone Granite for advice or service.

Stain Removal Guide

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Stains can be categorized as...very light, light, moderate, severe, and very severe.

Moderate to very severe oil stains in granite and quartzite can prove to be stubborn to
remove using a commercially premixed poultice.

If you have moderate to very severe staining of any kind or you're not quite sure what
caused the stain it is recommended that before you attempt to remove the stains that
you consult with a qualified stone care professional first.

In your Stain Removal Kit you will need...

• Tape (tan painters tape 2 to 3 in. wide)
• A wooden or plastic spatula
• Plastic (food warp, etc.)
• Hydrogen peroxide 6 to 35%, the higher %
  can be bought at a beauty supply store.
• Ammonia, bleach
• A product named "DI DI Seven" and "Iron Out",
  KMart, WalMart and some hardware store sell them.
• Acetone, lacquer thinner these are solvents that can
  be bought at a hardware stone. They are safe to use
  on all types of stone.
• A nylon scrub brush and rubber gloves

Stain Protection

The stone should be treated with a water and or oil repellent. These types of treatments modify the absorption factor of the stone and minimizes staining.

There are several factors to consider when choosing a sealer for stain protection.

• The type of stone ( marble, granite, etc.)
• Its absorption %...See Stone Types
• The type of finish...Polished...Honed...Textured
• The stones location and the possible staining conditions.
• The Color Clue chart above will give you an idea.
• Is the product ( sealer ) formulated for a dense stone or
  for a stone with large pores? Sealers are not alike in certain respects.
• What is the service life...6 mos.,1, 2, 5,10 yrs. This is how long the
  product will work before it needs to be reapplied.
• Will the product darken the stone?
• The products and methods used to maintain the stone after it is treated.
  Some products and methods will shorten the sealers service life.

It is important to understand what a repellent treatment will and will not do.

They will not prevent etching from acidic foods and beverages on marble and limestone.
However, a treated surface will minimize the degree of etching by keeping the offending
substance at the surface not allowing the damaging effects to migrate deeper into the
stone to cause severe etching.

A treated surface is not a total guarantee against staining. Repellent treatments
are not stain-proofers. If an offending substance is left in contact for a prolonged period
of time a stain may develop, however it will not become deep seated. Therefore, care should
be taken to remove any spills or foods from the surface as soon as possible.

Treating the stone does not make it maintenance free, it still needs to be maintained
with the proper stone care products. Honed and texture surfaces in interior settings will
receive further protection from using a "stone soap". Stone soaps dress the stone leaving a
residue behind which may act as a sealer and a soil releasing agent.

Understanding stone and the products that are available for stone care leads to realistic
expectations and are vital elements for a successful stone maintenance program.

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