WE STOOD in a semicircle around a long table in Washington's Textile Museum, each clutching some timeworn family treasure: a quilt, a carpet, a shawl, a wedding dress, an ancient sampler.

It was First Wednesday, the day each month when the museum holds open (and free) house for people who need to know what to do about dear Aunt Isabella's yellowing lace mantilla, or Great Grandfather Smiley's moth-eaten, homespun butternut Civil War breeches.

One by one we stepped up to plead our cases to conservator Jane Merritt, who spread each offering on the sheet-draped refectory table and examined it carefully, testing the textures and stitching with gentle, knowing fingers. We looked on, solemn and attentive as jurors at an inquest, awaiting her verdict.

Here was Mrs. G., with the little carpet that she and her mother and her mother's mother had stood on when they were married. When she got it out in anticipation of her daughter's wedding, she found the fabric full of holes.

"I never dreamed there were moths in it," Mrs. G. said in a small, guilty voice. "I know it's not a fine carpet, but, well, it's a family tradition, and I'd like to save it if it's at all possible. I mean even if it costs so much that it wouldn't make sense."

"It's a very nice carpet," Merritt said, "and you're the only one who can say what it's worth. I would regard something with such a long tradition behind it as priceless."

She turned the carpet in her hands and pursed her lips. "This doesn't look like moths, it looks like the sort of damage carpet beetles cause. And the fibers are too supple for it to be dry rot." She looked up at Mrs. G. and smiled. "A rug dealer -- by that I mean a serious dealer, one who handles antique carpets -- could restore it to look like new."

Mrs. G. smiled. We all smiled. If this ratty- looking piece of carpet wasn't hopeless, then there was hope for us all.

A young man stepped up with a brilliant primitive Caribbean tapestry that had been glued to particle board. Merritt shook her head sadly. "I can't recommend that you do anything with this," she said. "It's going to self-destruct, but probably not in your lifetime. Perhaps before it's too late someone will develop a method for getting it off that backing without ruining it."

The young man's face fell and we all frowned in sympathy. He thanked her and walked slowly out of the high-ceilinged room, holding the tapestry in front of him like a herald leading a funeral cortege.

Next was an old China hand with a large swatch of ancient Laotian silk. Almost weightless, the midnight-blue fabric shimmered with gossamer threads as she swirled it onto the table to display the deep and permanent crease that had developed along a fold. "I want to mount this for a wall display," she said, "but it's too big and won't lie flat, so I thought I'd cut it across here and overlap it."

"Oh, no," Merritt gasped, then curbed her tongue. "I mean, of course you may do as you see fit, but it's a fundamental principle that we never cut anything unless we absolutely have to. You can bring the borders in and hide the crease by folding it, so" -- she did some magic with her hands and the cloth lay in an artless rectangle that was just right.

Merritt sometimes knit up a raveled sleeve of care and sometimes dashed a hope, but was always and endlessly patient. The treatments she recommended were generally extremely simple: gentle vacuuming, minimal stitching, patching instead of reweaving, learning to live with a stain rather than risk widening the discoloration. Most often she said to seek professional help, "which unfortunately can be hard to come by, and very expensive."

Eventually it came my turn to show Great- great-great-great-great Aunt Olivia's sampler, sewn when she was eight. It had followed the family from New York City to Abilene, Texas, to Maryland's Eastern Shore and to Arlington. Lost in a move 25 years ago, it was found last fall, folded in one of a stack of moldering books in a leaky shed.

Brown with age, mouse-nibbled, colors faded, the little scrap of linen is all the dearer to us because of the uncertain stitches and backward, skipped and out-of-sequence letters. It seems to have been done with tatting rather than embroidery thread, and it's a hodgepodge of random hues; we like to think of little Livy filching remnants from mother's sewing box and working in some secret corner of a house in Harlem, preparing her surprise: Olivia Van Tuyl Her Work May 28 1806.

"Oh, this is lovely," Merritt said. "It's in good shape, for its age. What a wonderful thing to have such an old family piece that's documented." She looked it over critically and then looked me over, perhaps more critically.

"You may not want to try to work on this yourself," she said gently. "It will certainly have to be steamed to relax the folds, and probably should be washed to get the dirt and acids out. The techniques involved are extremely delicate, and I'm sure you wouldn't want to take a chance on damaging it."

"My sisters would kill me," I said, writing down the name of the professional fabric conservator she recommended.

Again and again Merritt repeated the cardinal rule of fabric conservation: Doing nothing is almost always far better than doing the wrong thing or doing the right thing wrong.

"Many of the fabrics that are brought to these workshops are being slowly ruined, by improper hanging, by dirt, by ultraviolet light, or by careless storage," she said as she unwound over lunch after the three-hour session. "But that's better than having them quickly ruined by drastic efforts at restoration.

"People come to the museum looking for solutions, and they're often disappointed that there is no solution to a particular problem, either because it would be too expensive to save a given piece, or because no safe method has yet been developed. As a conservator you have to be ultraconservative, because the whole idea is not to make things worse."

Merritt, 31, has always been fascinated by fabrics, and taught herself to sew and weave when she was little. She did curatorial work at the Cooper-Hewitt Museum and conservation at the Metropolitan Museum in New York, as well as spending a couple of years studying in Europe, before she came to Washington to mount a show 21/2 years ago and wound up on the Textile Museum staff.

She's been doing First Wednesdays for two years. "In a way I dread it," she said. "It's a terrific responsibility. People, particularly those who sew or weave, think they know a lot about fabrics and expect to do the work themselves. But it just isn't that simple, and I usually have to tell them to take it to a professional or just leave it alone. There have been fantastic strides in fabric conservation in the past twenty years and there'll be twice as much progress in the next twenty; meanwhile, we just try to preserve many of the textiles whose condition now seems hopeless.

"Every session is much the same, but each is also very different. Last month I had an absolutely stunning Persian carpet, apparently formerly the property of the Shah; today it was the colors, so many vividly colorful things that came in."

Merritt's midday workshops are complemented by simultaneous fabric-identification sessions in a nearby room, and on the first Saturday of every month the museum is thronged with rug owners trying to discover -- or verify -- the origins of old carpets they've bought or inherited.

The reputation and authority of the institution have become so widely respected that when Sonia Gandhi, wife of the Indian prime minister, came to Washington with him this month, the Textile Museum was one of only two stops designated as "musts" on her itinerary. Mrs. Gandhi, herself a noted fabrics expert, spent several hours in the conservation lab with Merritt.

Cynthia Sapia-Bosch of Bethesda, the conservator Merritt sent me to, confirmed that the sampler's in pretty good shape for the shape it's in. Washed and mounted on acid- free backing and beneath air-permeable but ultraviolet-proof Plexiglas, she said, it'll be something the family can fight over for a couple of centuries. UNRAVELING TEXTILE MYSTERIES

The Textile Museum is at 2320 S Street NW. Fabric conservation and identification workshops from 11:30 to 1:30 (or whenever) on the first Wednesday of each month (call ahead). Rug appreciation workshops at 10:30 on the first Saturday of each month. Museum hours: 10 to 5, Tuesday through Saturday, 1 to 5 Sunday. Suggested donation of $2 adults and 50 cents for children. 667-0441.