Adrien Arpel knows it is only the rare woman over 30 who hasn't stared at the TV, in the awe of the actress her same age "who has aged more slowly."

Arpel has done it herself. And even though she knows that the actress has a whole battery of professional working wonders with make-up and dress.

"You have to be born beautiful to be beautiful," says Arpel. "But woemen who are not really pretty, and are in their 30s, 40s, 50s, can greatly boost their appearance by looking 10 years younger." 3

It's important not only in the job market, maintains New Yorker Arpel, but in every social situation. "A man of 45 can go to a cocktail party, and every woman from 20 to 55 is a possible choice for him. A woman leaves with a younger man, and everyone finds it embarrassing."

Arpel said she was impelled into doing a second book, "How To Look Ten Years Younger" (Rawson, Wade Publishers, Inc., $14.95) as the result of questions asked by women at autograph parties an book-signing events.

"I've been dieting, I have three kids, I've done every facial exercise and I still have a double chin," one woman told her. "I lost 20 pounds and I still have a pot belly," complained another.

(Arpel met Patty Snyder, who travels with her to show off makeover changes, in a California department store when she came to seek Arpel's help.)

Most women, she says, know about diet and exercise, but don't know how to find clothing and cosmetics to improve their looks.

Arpel remembers the day she turned 30 and put on a low-cut dress, as usual, with a soft bra. "My bosom had fallen. I looked awful," she says. aI swore I would never wear anything low-cut again."

After a thorough study of the brassiere market, she learned, and has put in her book, an in-depth evaluation of different types of bras and girdles for specific figure needs.

If you know the language, these products, such as minimizers, demi- cup, push-ups, are available at discounters, as well as in expensive department-store brands," she says. "Certainly there are few saleswomen around to give assistance like the old corsetiere with the tape measure around her neck."

She also concludes that support hose not only help shape the leg, but give it a smooth look under pants, and can help a fallen derriere. "And they wear far longer than regular panty hose."

Arpel claims her new book has "zero repeat" from her first, "adrien Arpel's 3-Week Makeover, Shapeover, Crash Beauty Program," which sold 450,000 copies in hardback and was the No. 1 best seller for several months. ("My husband would look at the New York Times best-seller list and say, 'My God, the book of a brilliant economist is number 14 and YOU are number 1.'")

Included in her latest offering are formulas for making beauty products at home, which would seem to be in direc t competition with her own $13-million cosmetic business (started at aged 17 with baby-sitting money). "Women won't accept things without questions as they did five years ago," she says.

"They want to know what is in each product, why it costs what it does. Women are no longer satified with the promise of magic."

Her "brown-bottle formulas," she says, are breakdowns of products used in the best European spars. For her own commerical cosmetics, she has added preservatives and regrouped ingredients to meet government regulations.

In her book, she gives recipes for turning raw ingredients -- not found in drug stores -- into natural treatments. Her Swedish freeze, for example:

Fill an ice tray half with mineral water, half with astringent (or half lemon or lime juice), and two pinches of alum. Return to freezer with icecream stick in each cube. Rub a cube over the face to soften the appearance of wrinkles by tightening the skin around them.

"It is an old trick for European actresses who haven't gotten enough sleep and need to make an appearance in the morning," says Arpel, who uses it herself. "It takes out the puffiness, freezes the lines which stay hidden for hours under makeup."

Among items on her beauty shopping list: soybean oil, aspirn, vitamins, lecithin, liver, glycerine, seaweed, kelp, ginseng.

In her book she also tackles the subject of cosmetic surgery (particularly what it won't do for you). For smoothing facial lines, she recommends acupressure face-lifting, rather than the acupunture variety.

Arpel points to the sun as the major contributor to premature aging of the skin. She believes sun screen and sun block are "essential, even for such short-term periods as a set of tennis." As a doctor once told her, "Do you know what I call women who like to sit in the sun . . .patients."

And finally, it must be said that Arpel looks 10 years younger than her 39. Her bangs -- worn like her 17 year-old daughter Lauren's -- conceal, she admits openly, some forehead lines.

And the Bulgari jewelry? "It helps to have a little Bulgari, but only if you are doing all the rest. The jewelry shouldn't look better than you."