TOM LYNCH was waiting impatiently at the St. Louis airport one summer day in 1969. He was hot and his flight to New York was delayed. With nothing better to think about, he noticed that the west side of the airport, where he was standing, was burning hot in spite of the air conditioning.

Then he saw why. The high and wide windows that lined that portion of the airport were dressed with plastic, vertical Venetian blinds. "They were completely ineffectual. The sun had entered the windows and nearly melted the blinds. Where the individual slats weren't entirely distorted, they had come loose," recalls Lynch.

"I then walked over to the other side of the airport, staying on the same floor. It was cold. Here the sun wasn't hitting the glass directly. (It had moved in the afternoon to the west.) The air conditioning was turned on full blast, even though you couldn't feel it on the west side. It was then that I realized that something was needed that wouldn't shrink or stretch -- something you could use in place of plastic."

Metal Venetian blinds won't melt, but when they're drawn, you can't see out. Keeping this in mind, Tom Lynch invented the solar screen -- becoming the "Granddaddy of Fiberglass Screening," as he is known around J. P. Stevens, where he was employed.

"I wanted to find something that was woven in construction, but that you could see through; something that would maintain the design that the architect had intended -- as in those large airport windows."

Lynch made the first solar screen while he was vice president of the industrial fiberglass depaprtment at J.P. Stevens & Co. 11 years ago. It was, and still is, constructed of fiberglass. The screen allows you to see outside, as do glass windows, but at the same time controls the entering solar light.

Lynch made the screen at J.P. Stevens' Slater, S.C., plant. He started with a base of fiberglass yarn. This raw material is produced by companies such as PPG (Pittsburgh Plate Glass) and Owens Corning Fiberglass. Lynch then covered the yarn with polyvinyl chloride (PVC) to provide durability and color. Next, he grouped seven or eight coated yarns together to make a larger filament. These filaments were then woven together on a sulzer-type loom to form a 54-by-18-inch construction, and voila!

The glass should be installed on the outside of a window in the frame of the old screen or in its own metal frame. The frame can be a four-sided or a mounted-tension frame. If you use an old screen frame, simply remove the old insect screening and insert the fiberglass into the spline. (The spline is the plastic/rubber lining.) The screening comes on a roll and can be cut down to the size you need. The screen frames usually are purchased separately.

"Solar screens," says Clyde Warren, manager of customer service for coated-yarn products at J. P. Stevens, "block between 60 and 70 percent of the solar heat coming in through the window, due to absorption and reflection. Colors such as gray, charcoal and bronze are dark and absorb more light than they will reflect." Instead of the interior of your home getting hot, the screens reflect, absorb and dissipate the heat before it reaches the glass. tSolar screens make even non-air-conditioned homes cooler.

J. P. Stevens spokesman Warren says that a room with two windows that receives direct sun could be as hot as 92 degrees. With solar screens -- and no air conditioning -- the room can cool down as much as 10 to 15 percent. The screens are usually made in the above three colors, although both J. P. Stevens and Phifer Wire Produces make them in white for windows that open out. White screens are used primarily on the interior of the window. They are only 50 percent effective in blocking the sun; since they are installed on the inside, the heat has already penetrated the glass and some gets inside your home. According to Lynch, "White fiberglass works best for windows that open out. With white screens, the solar heat penetrates the glass and hits the screening. The heat is reflelcted off the screening and bounces out through the glass."

J. P. Stebens & Co. and Phifer Wire Products are the only two companies that produce fiberglass solar screening material. Other companies manufacture the end product -- the screen itself -- but all of them buy their fabric from either Stevens or Phifer.

Phifer started making the solar screen material four years ago, while Stevens got the product underway when Lynch and a fellow J. P. Stevens employe, Harry Detricks received a patent for it in 1970. "Our biggest problem," says Phifer's advertising manager, Bill Benton, "is getting nationwide distribution. Despite our wideranging advertising campaign and our membership in the Screen Manufacturers Association (SMA), the distribution of the solar glass screen is relatively small."

Clyde Warren of J. P. Stevens echoes these sentiments: "Yes, distribution has been a problem. But J.P. Stevens and Phifer are now working through the SMA and the Screen Weavers Association, who are in turn coordinating the distribution effort."

Since the screens are not that new a product, why -- besides their poor distribution -- haven't we heard more about them?

Warren of J.P. Stevens thinks it's because "it hasn't been until recently that householders have become so energy-conscious." James C. Plunkett, market manager of decorative yarn products of PPG Industries' fiberglass division, says that the shading device has been used by commercial building owners for more than 10 years to reduce glare and air-conditioning costs, as well as for its attractive appearance. "It's only been in the last couple of years that solar screens have become available for residential applications."

And being energy-conscious can be good for your budget. The solar screen is eligible for tax creditt, since it is "a solar or wind device that is used to conserve energy." This is one of the definition of an eligible credit, according to Milton Friedman of the Internal Revenue Service.

Solar screening costs 50 to 60 cents per square foot on the roll, or if you buy the screens made, it will cost $2.50 to $4 per square foot. The latter cost varies depending on whether you live in a highrise, since cranes need to be rented or window-washing rigs need to be hooked up for installation of the screens. "Suncheck," a custom solarscreen manufacturer based in Richmond, Va., sells the screens already made up. The Reynolds Company, also based in Richmond, sells the materials needed to make the screen and leaves it to the homeowner to assemble it himself.

Hechinger's sells the fiberglass screening at $17.49 for a 48-by-84 inch piece. They also stock Reynold's aluminum frames. Solar screening may also be found in Ace Hardware stores, True Value Hardware Stores and American Hardware Stores.

So, now 69-year-old Tom Lynch, father of the fiberglass solar screen, has a patent under his belt. He has moved to Dade County, Fla., as a manufacturing represntative for J.P. Stevens: Is he rich and living happily ever after?

"Well," he laughs, "I'm living happily enough, but my golf game's not as good as I'd like." But he's keeping his cool -- and helping others keep theirs.