When Percy O'Keefe promises a tonic for hot weather, he delivers. In fact, Percy O'Keefe not only drives the delivery truck for the Butterfield Bottling Co., of Old Town, Maine, he first loads it with bottles he has washed and filled with soft drinks he has mixed from formulas that are "mostly in my head."

One of only two employes of Butterfield Bottling Co., the other being his wife, Orisa, who keeps the books, O'Keefe is also "janitor" for, as well as owner of, the 74-year-old firm.

O'Keefe's operation is an anachronism; likewise the term "tonic," as in "I'll have an orange tonic," which New Englanders used to use when they went in the corner store for a soda pop, seems quaint.

Nowadays, "soft drink is what most people say," says O'Keefe. "Defines it from hard drinks, I guess."

And, in the age of mergers and conglomerates, the average large bottling plant produces more soda pop in one day before lunch than Butterfield Bottling produces in one year, according to figures of the National Soft Drink Association. O'Keefe annually bottles 6,000 or 7,000 cases of his S&O'K brand soft drinks for distribution across a small swath of eastern Maine.

It's a true mom-and-pop operation that has O'Keefe driving as far north as Millinocket, as far west as Pittsfield, east to Clifton and "down the coast to Trenton," he says, though his best market is right there in Old Town, nearby Orono and Howland.

Trenton is, of course, Trenton, Maine, on the mainland side of the causeway to Mt. Desert Island, Acadia National Park and tourist-inundated Bar Harbor.

"Don't go on the island in the summer," says O'Keefe, "it's too crowded."

Thus, the tourists don't even know what they're missing and, since most of them seem to be rushing from one gift shop to another, seldom stopping at the small, independent groceries that are the backbone of O'Keefe's business, perhaps they wouldn't care.

If they did stop to pop the cap of an S&O'K tonic, they'd find that it comes in 10-ounce returnable bottles and, though orange is the best seller, in such old-time flavors as cream soda, sarsaparilla and birch beer, as well as strawberry, root beer, ginger ale, lemon-lime, punch, cherry and, at the bottom of the popularity list, cola.

And, if there were a demand for all of those flavors in Trenton, N.J., or at your local Giant supermarket, you would assume that Coca-Cola and Pepsi would be producing them. While the chain stores have "all the franchise stuff," according to O'Keefe, and "the biggest problem is getting cooler space," there is a demand at the mom-and-pops that dot Maine.

It's the birch beer, however, a taste somewhere between root beer and cream soda, in addition to the diminutive size of the operation, that sets S&O'K apart from the national brands with their slick advertising campaigns, jealously guarded secret formulas and caffeine-free, sugar-free variations. The birch beer and the nostalgia.

But for old-timers in Maine who remember the bottles that S&O'K came in for years, stenciled with rushing water, a mountain and a pine tree, times are changing. Now, all the bottles have is a little circular white label that says "Butterfield Bottling Co., Old Town, Me.," in small letters and that, in larger figures, notes the 5-cent deposit required by the state bottle law. O'Keefe does still have some of the stenciled quart-size bottles that he no longer markets, but fills "for friends."

O'Keefe's is a small world. Not only can he drive his entire marketing area and be home for supper, but he literally lives over the store. The Butterfield Bottling Co., is on the first floor of a two-story gray building in the Great Works section of Old Town, across the road from a paper mill.

Upstairs are two apartments, one occupied by the O'Keefes, the other by their daughter, a schoolteacher, and her family. Their son-in-law "builds canoes" for the Old Town Canoe Co., which is internationally known to those who buy canoes.

Neither is interested in the business, which has been in the family since 1922, so when O'Keefe, who is 64, decides he has had enough, the Butterfield Bottling Co., and its birch beer, will pass either out of the family or out of existence.

There are approximately 1,500 bottlers in the United States, according to Cheri Lofland of the National Soft Drink Association, including the big regional franchises, and the number has dropped dramatically over the years because of mergers and acquisitions.

Butterfield Bottling, which was founded in 1910 by Mort Butterfield, was purchased in 1922 by O'Keefe's uncle, Harold Spruce, and his father, Donald O'Keefe, hence the S&O'K brand. Percy took over in the mid-1950s, though his father, now 95, still "lives up the street a ways."

O'Keefe has had inquiries from potential purchasers, but "most of them don't have any money," he says. "They want me to hang around for a couple of years and help out, so I might as well keep it."

So, as long as he does, when O'Keefe goes to work, he just goes downstairs. There, the entire operation is contained in an area smaller than some of the stores that sell his product.

"I'd say the building is approximately 20 by 80 [feet] ," says O'Keefe. "I never really measured it; I'm just judging by the way my truck fits in."

In the front is the office with a desk; a big, old safe with large old-fashioned lettering that says Butterfield Bottling Co.; and little else.

The safe does not contain any secret formulas; that's "mostly in my head," says O'Keefe. "It's not like Coca-Cola."

In fact, O'Keefe does have the formulas written down somewhere, "but I've done it so many times that it comes natural," he says. "I mostly eyeball it. You blend a little of this and a little of that and sometimes you make it a little better, or you think it's a little better."

And, sometimes, he admits, "a batch will be flat."

That's because, in the back of the building, in the mixing-and-bottling area, which is behind the truck bay, which is behind the storage area, which is behind the office, it all comes down to whether O'Keefe gives the correct valve the correct twist and mixes the right amount of CO2 with the right amount of water.

He breaks up blocks of dry ice, puts the pieces in cylinders where they turn to gas, which is heated and piped to a carbonator, where a paddle agitates and mixes it into filtered city water. O'Keefe adjusts the amount of carbonation in the water according to the flavor.

"Ginger ale is high in carbonation, orange low," he notes.

Above, on a balcony, are two vats. In one, O'Keefe mixes 100-pound bags of fine granulated sugar with water to produce sugar syrup. In the other, he mixes the sugar syrup and flavor concentrate in 50-gallon batches that are gravity fed to the bottling machine below.

The bottling machine, which looks as if Rube Goldberg had a hand in its design, is actually a washer, bottler and capper in one.

"We've had it 40 years and we got it secondhand," says O'Keefe, who doesn't really know how old it is. "Of course I could look it up and find out but I never cared for that."

As for maintenance, O'Keefe notes, "You can't go up to the hardware store for these parts." He saves them from abandoned machines and has "a friend who's a pretty good machinist. I'm waiting for him to fix something now."

The washer/bottler/capper cleans four bottles at a time and then sends them around a conveyor to get a squirt of flavored syrup, then carbonated water, then caps, or crowns as the old-type compression caps are called. No twist-off caps here. After that, he puts the bottles in cases -- by hand.

The machine holds 360 bottles at a time, which makes a 15-case lot the minimum that O'Keefe bottles in one batch. In winter it may be once every couple of weeks, as consumer demand requires, in summer three times a week.

"You have to make your living in the summer," he says, noting that on a snowy day (and Maine has a lot of them), "you don't see many people walking down the road drinking soda."