Fans of the PBS program "Antiques Roadshow" will know the moment well. The appraiser pauses before giving the value of a piece and then says, "If you hadn't cleaned it . . . " And you know the rest.
So how can you determine if you're reducing the value of your old chair or cabinet by cleaning it, or if cleaning the piece will not only improve its look, but prolong its life and usefulness?

According to Jerry Van Slambrouck, interior design instructor at The Art Institute of California - San Francisco, before attempting to clean an antique or mid-century wood piece (including the '50s), seek a professional opinion to determine its value.

A reputable antiques dealer is usually a good source. If you can't transport the actual piece itself, Van Slambrouck recommends taking pictures of the front, back and sides, as well as close-ups of any details.

"I have taken photos of pieces to shops that deal in a particular period for advice and they're usually very happy to help and excited to see the piece," says Van Slambrouck. If an antiques dealer or other expert is uncooperative or just makes an offer to purchase the piece, he suggests moving on to another source, for example, a local ASID (American Society of Interior Designers) chapter or the ASID website at www.asid.org.

Once you know the value of your piece, and you decide you want to take on restoration yourself, you'll be happy to know that the products used to clean or strip old furniture have come a long way.

Chris Natale, interior design instructor at The Art Institute of Phoenix explains that "Before you would need real protective gear like rubber gloves, a respirator and goggles, but today there are so many different products, many of which are water-based and generally easier and safer to use."

Start any furniture restoration by working in a well ventilated space, says Khoi Vo, an interior design instructor at The Art Institute of California - Orange County.

Start by taking a small amount of paint thinner on a soft, clean rag and begin working on a hidden area of the piece to determine how the solution is affecting the wood. If it's working well, says Vo, then continue to clean the rest of the piece.

The paint thinner will clean any residues and dirt that have collected through the years. After it's cleaned, "You'll have a much better idea of what kind of repairs may need to be made," she says.

If you're restoring an old painted piece, try a diluted solution of face soap on a soft cloth and then immediately dry it with another soft cloth. After cleaning, you may want to try and tackle wobbly legs or joints. A good wood glue can take care of many simple repairs.

Once repairs have been made and the piece is cleaned to your satisfaction, Kim Morrison, interior design instructor at the Bradley Academy of Visual Arts in York, Pennsylvania, suggests playing with different finishes such as crackling, sponging, glazing or color washing, as a great way to give an old piece a whole new look. A local craft or paint store is a good place to start for information and supplies.

She recently helped a friend design his new dental office. At a flea market, she found a "seen better days" bureau as she describes it, and used stenciling, sponging and crackling techniques to turn the piece into "a focal point in the waiting room that also serves as storage for children's games, magazines and dental literature.

"Think of old furniture as a canvas, a place where you can create a 'one-of-a-kind' piece of art," says Morrison.