It was early in the morning, but the lobby of the Washington Hilton was filled with disoriented people. In coats and ties and T-shirts and jeans they rushed about, and only a few seemed to know whether they were rushing off to a seminar or the bus tour of Washington that was leaving outside.

Over by a pillar near the registration desk Sande Webster stood laughing - perhaps because she's been to seven of the eight national conventions of the Professional Picture Framers Assn., but maybe because she has a degree in physics and, at least yesterday, better understood the nature of the universe.

"I think it's wonderful," said Webster, dressed all in black and wearing a wide-brimmed straw hat, "you go to an AM convention, you meet all doctors. Here you meet people from all kinds of different backgrounds."

Therein lies the discreet charm of the PPFA convention, since, it seems, nobody sets out in life to become a picture framer. Organized eight years ago by six Californians, the PPFA checked more than 4,000 members into the Hilton and the DuPont Plaza down the street, all in town to borrow ideas from each other and to see the latest in circular mat cutters on the exhibit floor below.

Webster was going stale in a Philadelphia suburb after her children went off to school; she wanted to do something in art, she said, so she apprenticed herself to a framer for seven years. In 1969, she opened her own gallery and framing business. "My husband didn't want his little woman working," Webster said, so she ended up getting a divorce and moving into the city and marrying a design director at a Philadelphia advertising agency.

"Some of the people here are good with their hands, others have creative minds," she said."Both can profit. I have this theory that we're all born creative, but you go to school and the teacher says there's no such things as a purple sun, and you lose it. That's what this convention is all about."

Up the hall in one of the small conference rooms people were packing themselves in to hear Fred E. Webster (no relations to Sande Webster), a tall courtly, southern gentleman who, with his white goatee and mustache, looked more like a framer of the Declaration of Independence than of pictures. He was conducting a seminar in authenticating prints.

"Not so long ago, a framer's business was in reproductions, but now more people are buying original prints, and somebody has to say what's what," Fred Webster said. And a good picture framer he said, has to know his way around lest he be switched.

Being "switched" refers to the shady practice of sending a framer a reproduction of a picture the customer already owns to be framed. Then the reproduction comes back, the customer pulls out the bill of sale for the original, claiming switch and crying fraud.

So intent were his questioners that they kept Fred Webster nearly an hour after class. "Now Currier and Ives, for instance," Fred Webster said in reply to one woman, "look at this print through the glass. See the grain the stone left?" She couldn't.

"Well, I tell you about most Currier and Ives prints," drawled Webster. "They had an assembly line 50 years before Henry Ford, paid girls to paint in the outlines just like a coloring book as the prints moved past. Sometimes you'll find a green cow or something where they got to talking - sometimes you'll find a print where something's got no color at all." Webster smiled a riverboat gambler's smile at the woman. "That's a real find."

"I still don't think I could tell. Could I send it to you on consignment?" she asked.

Webster threw up his hands. "No ma'am. Then you're talking switch. You bring it to me - I live in Arab, Ala. You can't miss it - it's right in the middle of Hog Jowl, Scant City, and Egypt. Where you from?"

"Omaha," said the woman.

For all his down-home manners, Fred Webster is a pretty shrewd man, even as he says, "Dice is better than authenticating old prints - with dice you know the odds." He has been an authenticator for eight years, but before that he was chief industrial engineer at NASA in Houston, having followed Werner von Braun to Cape Canaveral from Redstone Arsenal in Huntsville, Ala. While at Redstone he got to know Arab, and decided to move back there when he retired.

"I have a good life," Webster said, "I only work about six months and 200 hours out of the year, and I never go north of the Mason-Dixon line." Arab suits him just fine, he said. But the other six months of the year?

Webster looked sideways out of his long face, and his lip curled in genteel disgust, the disgust of a wine connoisseur whose guest has just asked for a jug wine. "I contemplate my navel," he said, the gravity of the syllables his own eloquent defense of rural living. "I moved to Arab because I knew I'd live longer there than in Houston.If I wanted to make this more than an educated man's hobby, I'd move to New York or Washington," he said, and gesturing after the Midwestern lady with the Currier and Ives print, "or Omaha."

The convention was a mixture ranging from professional esthetes to hard-nosed small businessmen. A few years ago William Sethrie took the expertise gained in 14 years in the New York business world and opened a framing business in Fresno, Calif. Sethrie, dressed in a smart blue linen suit and white shoes, told the conventioneers about the success he had with his own TV commercial.

"I got Michelangelo up on a scaffold painting the Sistine Chapel left-handed," Sethrie explained, "and Michelangelo holds up one of my artist's lights and says, 'If I'd just had one of these, think how many ceilings I could have painted'!'" he grins. "I'm not going to make a living selling lights, but it might get some people into the store."

Downstairs on the exhibition floor, the selling was going on in a big way. Sandwiched in between the more than 350 displays of the tools of the trade - saws and mat cutters - and the hundreds of frame displays and selections of prints, was Dennis O'Connor of the Rising Paper Co. of Housatonic, Mass. The young O'Connor, one of the few people on the floor in a suit, was explaining why Rising Paper was the best to use to back a print.

"We put real linen scraps in our paper - we get them from Fruit of the Loom underwear. And the water we use comes from an artesian well right on the grounds - the water has a pH of 7." Neutral acid paper is the best; acidic paper can buckle and spoil a print.

"Come up and see us some time in Housatonic," O'Connor yelled. "The mill was built in the 19th century - we've got the only paper mill in the country that's a National Landmark."

At the other end of the hall, Sean Hunt was explaining to an interested couple how he suspended prints between glass, with no visible sign of support. Hunt was at the convention working for the Bainbridge Co., the largest maker of print matting in the country, but on his own time he runs a gallery and framing business in Manchester Center, Vt. like many people Hunt drifted into picture framing - in the '60s, he was a member of the New Christie Minstrels. But by 1971, he had tired of music and retired to rural Vermont.

"I began framing my own work, trying things nobody had ever done before because nobody told me not to. I can't complain. Excuse me." Hunt was off again to explain the suspension trick.

"My only regret is that I didn't get to enter anything in the new-ideas competition," he called over his shoulder. "I'm just too busy."

The competitions - one for framing, one for new ideas - are the hottest attractions of the convention. All along one wall of the narrow exposition space are strange objects in stranger frames: a bird's nest, butterflies, old matchbooks, even a stuffed owl, all under glass in a frame. But it is the other wall that commands the most attention - 76 reproductions of William Harnett's still life "My Gems" in frames that vary from standard wood to the one that drew the most attention, which included a quill pen, a china cup, and an old shred of sheet music, all objects from the painting.

"Can't say it's my style," said one man, examining the frame closely. "Pretty loud," his companion said critically, "but you know, it'll probably win. They go for something that stands out."