How would you feel if you ordered a bottle of wine in a restaurant, a good wine, and the waiter, after showing you the label, twirled his fingers, flicked his wrist, screwed off the metal cap and poured the wine for your approval? Exactly. There's no esthetic substitute for the cork. Cork producers and winemakers know that. They say that it is the strongest reason for the continued use of cork in all but jug wines. Other seals, metal or plastic, are plainly plebeian.

Cork, made from the bark of the cork oak tree of the Mediterranean basin, has been the most effective way of keeping wine in and air out of a bottle for more than 300 years. It still is.

For generations, it was believed that the spongy, resilient cork, made up of millions of tiny cells, actually allowed the transference of air. "The wine breathes through the cork," it was said. Today, the experts say that this is incorrect. There's enough oxygen entrapped in the bottle to help the wine to mature. The role of the cork, or any seal, is to prevent any more air from entering the bottle.

Then, in principle, could not a manufactured product, such as the ROPP metal cap (roll-on-pilfer-proof) be just as effective? Yes, and it's a lot cheaper. But, says Bill Scott of Scott Laboratories in California, a producer of finished corks and other seals, manufactured products are not fail-safe. As long as they have been fitted properly and the bottle's rim is perfectly shaped, there is no problem. But, any imperfection and the air will leak in. A cork, in contrast, pushes up against the inside of the neck, expanding to fill the spaces caused by poor quality glass, or an imperfect cut. Cork is more forgiving.

Yet we've been using the cork as a scapegoat for so many faults in a wine. Corked and corky are two of the bad words in the wine vocabulary. Scott says that less than 10 percent of spoiled wines are caused by faulty corks. The culprits are more likely to be found in the filtration and bottling processes.

So, we like corks because they look more dignified. And corks can do as good, if not a better job, than the substitutes. However, they do have a couple of serious disadvantages: supply and price. Portugal and Spain are the largest producers of cork, but they can't provide enough top quality material for the expanding international wine industry. It takes 50 years before the first crop of bark can be taken from the tree. Nine years are required for regrowth between harvests. Growing cork is obviously a long-term proposition and it's not surprising that there's a shortage of the better grades.

The universal puzzle for wine producers is how to find good corks and how to keep up with increasing prices. The standard 13/4-inch cork costs seven cents. The two-inch cork used for wine intended for long aging costs from 81/2 cents to 101/2 cents each. These are one-piece corks, stamped out of a single strip of bark. Less expensive alternatives are being developed, with names like composite cork and conglomerate cork, but their success to date is mixed..

An ROPP seal costs 11/2 cents. Perhaps we'll have to get used to the indignity of manufactured seals on those 90 percent of bottled wines that are not for aging. However, the cork is still the answer for the finest wines. If no expense has been spared in the vineyards and cellars, why risk all with an inferior or unproven seal?