MY FRIEND from Italy just had marble counter tops installed in her kitchen earlier this summer -- to remind her husband roll out pasta dough at least twice a week on the lovely, soft-to-the-touch counters. Recently, however, she wondered about cleaning the marble. "We want to be careful of what we use," she said "since so much of our food passes over these counters."

Cleaning marble involves more than just a quick sponging of its surface. Unlike the round gueridon tables of marble in the White House, whose tops are attended to by servants, average homeowners are on thie own.

Robert Hund, public relations director of the recently reestablished Marble Institute, says that the ring marks you may see on marble are either surface etchings or a combination of etchings and stains. Both are caused by acid substances -- wines, beer, fruit juices, carbonated beverages etc. -- that have condensed and slowly penetrated your marble. In the case of stains, the acid penetration has progressed further.

"Any acidic substance can break down marble, which is composed of calcium carbonate," says Jack Kelly, co-owner of Jack T. Irwin Marble in Rockville. "And," adds John F. Hardtke Jr., senior vice-president of Hilgartner's in Baltimore, "you don't necessarily have to spill the coke or fruit juice directly on the marble to get a ring. What usually happens is that the condensation that forms around the glass of the acidic substance comes in contact with the marble and this is what penetrates, leaving you with a ring."

Hund suggests you begin cleaning your marble-top table by wiping it down with just water. Then, "make a poultice out of blotting paper or paper napkins. Apply this to the marble's still-wet surface. The poultice should react on the acid stain by drawing out the stain -- like a mustard plaster was supposed to work on your chest cold." If the stain is oilbased, Hund suggests soaking the poultice in acetone first, being careful that the area is well ventilated since acetone is flammable. If the stain is organic (coffee, tea) soak the poultice in a hydrogen peroxide or household ammonia solution. This won't harm colored marble, claims Stanley Hornatko of Hilgartner. "The colors in marble are natural -- created by chemical compounds. Unlike the sun's ray's these bleaches are not on marble long enough to chemically react with its colors." Hilgartner's also uses a Comet Cleanser poultice.

To prevent stains in the first place, Hund says, "Apply a silicone or oilbased sealer on your marble. Marble is very porous and the sealer will fill in these pores, preventing acidic substances from penetrating." Hund says Hil-tex II and Onex-Seal II are two good sealers; both manufactured by Hillyard Products.

Beverly Ford, vice-president of Antonio Troiana in Beltsville, agrees "Marble should be sealed with clear silicone.Just pour it on; let it soak in. Repeat until the liquid can't be absorbed any further." But, Ford warns, "don't use polyurethane as a sealer. It cracks and will peel off. It also ambers and scratches easily."

Mary Bowen, a saleswomen Dept., krecommends a solution made of equal parts pumice powder and salt. "Mix them with water until the substance becomes paste-like. Apply it to the marble. Allow it to dry.Then remove." Pumice powder can be bought at most hardware stores. And Bowen says the salt from your table is just fine.

Or if you prefer ready-made mixtures, Bowen also likes Goddard's Marble Stain Remover ($2.50 for a 4 1/2 oz. bottle), used in conjunction with Goddard's Marble Surface Restorer (which is also $2.50 a bottle).

"Do not," says Bowen "use soap and water for regular cleaning. I use warm water mixed with a couple of teaspoons of salt. Apply this to the table top. Let it dry overnight. Then apply a polish." Ford of Troiano's is also reluctant to use soap, but says if you insist on using soap, use only very mild ones like as Ivory of Lux Liquid.

Also available and recommended by the Door Store in Georgetown and by Ellet Edwin's in the District, is Italian Craftsman, a liquid cleaner that is rubbed onto the marble with a soft cloth so as not to scratch the marble. It costs $4 per pint.

It's also important to know how to properly polish your marble. Bowen often tells her customers to apply Stanley Weyman's Marble Polish ($5 for a 12 oz. bottle) to new marble "once a day for the first week. This builds up a barrier between the actual marble and whatever you put on it. Following this treatment, Bowen claims, you don't have to apply polish for three to four months. "It's not good after this initial treatment to over-polish your marble since over-polishing will wear it down."

To get a professionally polished looked, Ford advises using a pumice stone and a hard buffing pad. Rub pumice into the marble until the buff returns.

But if your marble is past the point of no return -- where you can't get it clean and polished on your own -- then consider taking your table to a marble fabricator/installer. That will grind down the table, past the stain marks, and then repolish it to a fine gloss. Mayble comes in two finshes: a bright finish and a matt finish. The bright finish is pretty but due to its high-gloss look, scratches are more visible than finishes are mostly outdoors.

Area shops use special machines to redo table tops, charging between $20-40 an hour.

Ceramic Tile, 12240 Wilkins Ave., in Rockville, uses polishing stones of different grits (rough and smooth), then a pumice stone and finally a buffer to achieve a bright luster. They chare $37.50 per hour, and $15 for each additional half-hour. Ceramic Tile will give you a cost estimate once they've seen your table top.

At Franklin Marble and Tile, 6196 Central Ave. in Capitol Heights, md., the cost for cleaning, polishing and buffing is $25 an hour, which, says saleswoman Kay Bromwell, is usually enouh time to do a small table top.

And at Irwin's, 601 E. Gude Drive in Rockville, repolishing an average table costs between $20-30. Co-owner Jack Kelly doesn't believe that the average homeowner the rings over and over again," says Kelly "you just end up polishing the area around the ring as well, so the ring still shows."

Antonio Troiano, 10742 Tucker St. in Beltsville, Md., charges $25 per hour to repolish most marble tops, but more if the stains is very deep. If they have to they will grind the top off, says Beverly Ford, until they reach an untouched, undamaged surface. Then they return its original sheen by careful, consistent polishing and buffing.

And now for the pasta...