Detecting forgeries: knowledge is the best protection

A wave of collecting generally brings in its wake a beckoning signal to suppliers of the false in the fine-art and antiques market. It has happened a number of times before in history and appears now to be reaching new pinnacles of deception.

If the total annual turnover of large and small establishments, country sales , and small auctions were added up, the resulting figure would approach $3 billion. An expert has suggested that about 12 percent of this sum is realized by the sale of spurious copies fraudulently provenanced, reproductions that have been given the appearance of age, ''marriages'' of two or more broken pieces, and outright forgeries. Indications are that 1 fine art object in 8 will be a bad one.

The principal underlying reason is that the number of genuine articles from each artist or craftsman is strictly limited and cannot possibly meet the eager demand. Couple this with the fact that many people searching for treasures let themselves be guided by signatures, hallmarks, and makers' symbols rather than by the stylistic quality, the feeling of original craftsmanship that emanates from a master's hand. It is so easy for a ''floating signature'' to be placed on a painting or drawing, so simple to change the mark on a piece of porcelain, and only a matter of patience to fiddle with the hallmarks on silver or gold.

Not all reproductions set out to dupe collectors. The trouble comes at the succeeding sales, when the handler cannot resist the often large sums that can be made.

In 1845 the famous factory of Edme Samson et Cie was founded in Rue de Beranger, Paris. At the outset the intention of Samson was to help customers whose dinner services and other sets had been depleted through breakage; the factory would supply replacements. Over the years he and his staff became remarkably skilled at copying the productions of others. Examples of fine Dutch Delft, Meissen, Bristol, Chelsea, Marseilles, and Oriental ware poured forth. All pieces made were supposed to have been marked with an ''S'' to show their origin, and they generally had the mark of the factory being copied. But how easy to have overlooked putting on the ''S'' or for someone later to have abraded this symbol with a quartz stick or removed it with a drop of hydrofluoric acid.

Is there a field for the collector that is safe from the wiles and skills of the faker? The answer, regrettably, is a definite negative. Admittedly, today the scientist in his laboratory may have a number of highly efficient methods for proving an object is a fake, including X-rays, ultraviolet radiation, infrared rays, microanalysis, thermoluminescent dating, and pigment analysis. Very few fakes could successfully pass this trained scrutiny. But the snag is that the scientist has to be alerted, and it is quite impossible for every art object to be given such an examination.

You are liable to meet deceivers anywhere - dealing in antiquities, coins, documents, furniture, jewelry, paintings, prints, scientific instruments, sculpture, stamps, and even in the area of ''bygones'' or collectibles.

Yesterday's biscuit tins, for example, are faithfully copied and then given a ''distressing,'' a treatment that can include scratching, slight denting, staining, and other falsification. Gleaming pewter reproductions of 16th-century ware are lowered into tanks of viscous caustic solutions that can add the appearance of centuries in minutes. Present-day copies of 18th-century furniture by master makers are placed in humidity chambers that will produce the warping of centuries in a fortnight.

Another device of the spoiler is to break and restore. He knows that many people who see signs of restoration take these as statements of guaranteed authenticity. In fact, they should alert the buyer to undertake a very thorough examination.

What can help the would-be collector? Books can do much to build up knowledge and experience. So does a visit to a museum that is bold enough to display fakes beside originals. But the fact remains that when a new faker comes along, the odds are heavily on his side that the first productions will slip past all the guards available.

Look long at the object you have selected. Do not be hurried. Remember that the faker does not work with the free spontaneity of the original creative artist, but must copy with exactitude. Thus the more you look at a fake, the more it will die. Conversely, the longer a true original is regarded, the more the full beauty and truth of the master hand will stand out.