The big caution on tomatoes is not to can overripe ones." "If they're potholders, are they stitched tight enough so your fingers won't poke through?"

"There are some things that look better with a purchased button, and some that look better with a handmade button."

I'd always known there were schools for baseball umpires. Supreme Court justices start out by studying law. But a workshop to train county fair judges I'd never heard of before. When I read the intriguing announcement from the Cooperative Extension Service, I dropped my Whopper Junior and drove up to Waldorf.

Waldorf, mind you--home of the burger strip and the car lot--doesn't seem to be the sort of place that would foster what county fair folk call the "home arts." But the old Waldorf School, a staid relic just a few hundred yards from the hectic intersection of Rte. 5 and Rte. 301, offers a measure of peace and quiet, a feeling for time passed and enduring skills.

Here, 175 women (and a male or two) from throughout Southern Maryland gathered recently to learn what separates a blue-ribbon potholder from a merely serviceable one, why button style can knock a sweater out of the running and how to identify the quintessential jar of tomatoes.

Their instructors were extension specialists from the University of Maryland, their texts the homemade foods, crafts and clothing they brought themselves.

Cakes, pies, cookies and breads were clustered on a scuffed wooden table at the front of a classroom--mouthwatering specimens that would be mentally dissected in the morning and then consumed during the lunch break. In the auditorium, quilts, shawls, baby booties, embroidered pillows and an abundance of other handcrafted goods covered tables and hung from stand-up bulletin boards.

The homely old school, with its high ceilings and pale Venetian blinds, couldn't help but brighten it. Indeed, it was as if the women had set up a small-scale, one-day fair of their own. The spirit was one of serious amateurism, in which communal scrutiny and practical wisdom seeemed to thrive.

I am a lover of county fairs--of the spectacle, the noise and, above all, the livestock. (In my daily life, alas, I meet poultry mainly in the grocery store aisles and cattle in the form of an occasional Whopper Junior.) I must admit, though, that I rarely pay attention to the prizes awarded at the fair.

The one exception comes with the judging of the Holstein cows. Through an old connection to New England, I feel an affinity with the dairy farmer and his placid milker. And so, at the fair, I try never to miss the time when some gravelly voiced judge, carrying a microphone around the dusty ring, recites the praises of the best bovines.

To me, one of the great mysteries of the county fair (and of life itself, perhaps) is the concept of "dairiness," the term the judges also use to express their admiration of a cow when they've exhausted all the objective criteria, such as "configuration" and "cleanliness." Ah, dairiness! What heifer does not aspire to this blessed state?

At the workshop, the concerns were less metaphysical. It seems that for needle arts, home furnishings, crafts, food preparation, clothing construction and canning--the subjects covered in various sessions--firm standards can be made to stick. A crocheted item, for example, can be judged on appearance, design and workmanship, according to a sheet handed out by Judith R. Williamson, the specialist in housing and home furnishings.

Good workmanship, more specifically, depends on such factors as the execution of the stitching, the uniformity of stitching tension and the inconspicuousness of the yarn ends that are joined and woven into the piece.

Dorothy VanZandt, the food and nutrition specialist, pointed out to the prospective judges that, when confronted by dozens of jars of home-canned green beans, they could immediately weed out a bunch on technicalities. Did the entrant use the kind of lid specified in the fair rules? Did she use a mayonnaise jar instead of a standard canning jar? Is the jar clean?

Then there are more substantive matters. A jar of beans should not be cloudy at the bottom--a sign of overripeness. Nor should there be free beans floating on top.

Nevertheless, this science of judging is far from exact. What is "creativity," a key standard in the needle arts? How can you tell when a quilt design has a "pleasing rhythm?" The judging sheet and fair books talk about "suitability" and "appropriateness." These terms don't have the resonance of "dairiness," I grant you, but they go to the heart of the same elusive problem: good judgment.

Happily, this problem has never been neatly dissected--otherwise, we wouldn't have judging workshops. The extension agents and longtime fair officials at the Waldorf School were pleased with the turnout. The corps of fair judges needs recruits, they said. And the skills of veterans need to be honed.

After all, complaints about judging are not unheard of, even at a celebration as friendly as the fair. Those who came to the sessions in Waldorf will be able to judge at fairs throughout the state; the only restriction is they can't judge in their home counties, except for 4-H exhibits.

They'll undoubtedly find the experience rewarding. To judge at fairs is to have a kind of god's eye view on the state of creation. One travels among kindred spirits, with a practiced eye and an instinct for appreciation. Over the years, one comes to know the finer talents of the land--not by name (the contestants remain anonymous to the judges) but by their works. There is the lady in Calvert County who handcrafts buttonholes, the man in St. Mary's who lavishes countless intricacies on his wooden models, the lady in Anne Arundel who puts 50 layers on every decoupage.

Those who love judging love it, in part, for this engagement with excellence and for their contribution to its nurturing. As one judge with 12 years' experience told me: "I like to build quality in people."