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CLEANING MARBLE AND STONE

DESCRIPTION OF PROBLEM

There are several types of finishes and stain problems associated with marble and stone. This article will address the types of finishes as well as the types of damage and whether that damage is restorable.

NOTE: Before using any of the solutions below, test the treatment in an inconspicuous area to determine its effect on the stone.

DESCRIPTION OF SOLUTION

Marble is an alkaline material. Acids will eat into them and "etch" the stone. The following cleaning methods are safe for most genuine marble and other natural stones, but may damage other materials including some types of "cultured marble."

FINISHES

Polished: glossy surface that reflects light and emphasizes the color and marking of the stone.

Honed: satin surface with relatively little light reflection. Generally preferred for floors, stair treads, thresholds and other high traffic areas.

Textured: rough surface mainly used for exterior applications to avoid slipping or to create a contrast to polished or honed finishes.

STAIN REMOVAL

POULTICE METHOD

* Generally used for the removal of deep-seated, time-set dirt and grime. It is particularly useful on intricate carvings, moldings and other detailing.

* Mix white absorbent material (molding plaster, diatomaceous earth, untreated white flour, white tissue/paper towels, white powdered chalk, talc, Fuller's earth) with a common laundry bleach or a 6% solution of hydrogen peroxide to form a paste the consistency of oatmeal or cake icing.

* Apply the poultice (estimate at one pound of poultice/square foot of surface) paste to the stain (and surrounding area to prevent soil from being forced into clean stone). Use a plastic or wood spatula only to avoid the possibility of scratching the surface as well as to insure a uniform thickness of 1Ž2". Ensure there is full contact with the stone, leaving no air pockets or voids.

* Tape a plastic sheeting with masking tape over the poulticed area to concentrate and retain moisture. Allow it to set for 48 hours.

* After the setting period, dampen the poultice with clean, cool water to control dust. Remove the poultice with a wood or plastic spatula and rinse the cleaned area thoroughly with clean water; blot or wipe off excess water; allow to dry.

* Once dry, inspect for remaining dirt. A second poultice application may be necessary.

OIL STAIN REMOVAL (darkened stone)

* In order to remove this type of stain (a darkened area due to butter, milk, cream cosmetics, mustard, etc.) an acetone poultice must be used. [NOTE: ensure the area is well ventilated. Keep acetone away from sparks or flame]

* Apply the poultice in the same manner as above.

ORGANIC STAINS (pinkish-brown stain)

* Wash the surface with clean water and apply a poultice with a liquid base of hydrogen peroxide in a 6% hair-bleaching solution.

* Apply the poultice in the same manner as above.

* [NOTE: if the stain is from urine, a strong chlorine-bleach poultice should be used. For instance: If the area around a toilet is stained, sprinkle with chlorine-bleaching powder cleanser, dampen, and leave over night. Any etched marks can be removed with a marble re-polishing powder.]

RUST STAINS (orange to brown stain)

* Superficial stains may be removed with a vigorous scrubbing with a pH-7, 100% natural soap. Seated stains may be removed by the application of a commercial "Naval Jelly" or other rust remover, following manufacturer's directions for use.

* If this process fails, application of abrasive scouring powder followed by a second application of the "Naval Jelly" will remove the stain.

* If this fails, apply a poultice for not more than one half-hour using either sodium hydroxide (NH4OH), ammonia, or sodium hypochlorite (NaCLO), bleach, as the liquid base.

* Under no circumstances should cleaners containing bleach be combined with a cleaner containing ammonia since this produces toxic fumes.

PAINT STAINS

* Paint should be removed only with an acid-free paint remover. Do not use acids or flame tools to strip paint from marble. Follow the manufacturer's directions for use of these products.

* Use only wood or plastic scrapers and stiff fiber or jute brushes for removing the sludge and curdled paint.

* Oil-based paint stains will then need to be removed with the oil stain method above.

ETCH MARKS

* Wash the surface with clear water. Poultice the area following the above methods for your particular stain. Then polish: