A Plug for All Seasons
While the Practical Sailor editorial offices were being relocated this spring, a casual experiment was discovered—or rediscovered— on a windowsill behind a Venetian blind.
It's a cylindrical plug of solid epoxy, about the size of a frozen orange juice can from which, in fact, it came. The epoxy is in eight layers, which reflects the number of times it served as a mixing can for small repair jobs.
After the can was too full to be useful for mixing even one more small batch of what in the business is known (oh, so gracelessly) as "snot," the metal can was, on a whim, torn away. A couple of minutes with tin snips and pliers left a smooth cylinder of hardened epoxy.
"The Plug," as it came to be known, seemed ideal to confirm the oft-repeated warning that epoxy deteriorates in sunlight.
The date, 6/4/96, was marked on one end and the cylinder took up residence in a staff member's backyard, in an inconspicuous place that received full sunlight. It was examined from time to time, on no given schedule. On several occasions, it was thrown hard on a sidewalk and even battered with a hammer.
After four years, during which nothing untoward occurred, The Plug was taken to the office to be the subject of a small report. The date of its return, 2/17/00, was marked on the bottom, just below the original, still legible marking. Then it was placed on the windowsill—and promptly forgotten.
The Plug was rediscovered this past April. It had had another 14 months of sunlight, albeit filtered by common window glass.
It was thrown around and subjected to more hammer blows. Although not reinforced with any high-density filler, The Plug is still intact. It does have a few chipped edges. The expectation that it would at least crack or separate along the layer lines was unrealized. The epoxy does not even seem discolored.
It was time to call around.
At System Three Resins (3500 W. Valley N., Auburn, WA 98001, 800/333-5514) Nick Gucker, who has been formulating epoxy for a long time, said: "Yes, sun gets it. At the equator, 24 hours of sun a day, you'll see a thin coat blister and peel in two or three years—unless covered, painted or beefed up with an ultra-violet blocker, like our SB112 is. In non-tropical places, with average exposure, it'll go 6 to 10 years."
Gucker said our plug probably was lasting a long time because it's a chunk instead of a thin coat.
At Interlux (2270 Morris Ave., Union, NJ 07083, 800/468-7589), Doug Holmberg, vice president of marketing, said that a year ago he put a layer of his company's Epiglass on a bench in his backyard.
"It's going already," he said. "It doesn't peel like varnish, but it browns out and cracks sooner or later. Varnish with a UV additive lasts longer."
Like Gucker, Holmberg said he thinks The Plug will last a long, long time.
At Gougeon Brothers, Inc., maker of West System epoxy, Tom Pawlak said that over the years Meade and Jan Gougeon have built many molded plywood boats using clear epoxy-finished hulls protected with good varnish containing UV filters. One such was Hot Flash, still a very competitive racing boat. "We surveyed her recently," he said, "and found that although she's been raced hard for about 20 years, the finish is still good. She gets a coat of varnish fairly often.
"Without the protective varnish, epoxy will not last long…about like inexpensive or medium-priced varnish. It loses its shine, turns brown, and deteriorates."
Pawlak said he knows of a cabin cruiser in Maine that is natural wood with an epoxy and varnish finish. "The finish is 15 years old, but the owner does a varnish coat every two years. This spring, he said it's all letting go. He can get a putty knife down next to the wood. The old epoxy has a grip only on a few wood fibers."
Pawlak said he was surprised that Practical Sailor's plug was still intact, adding: "One of these days…"
Other than strongly suggesting that the thicker the epoxy, the longer it will last (a surmise that surprises few of us) the informal Practical Sailor experiment has made us think that another, slightly more formal test might be in order: a piece of teak or mahogany covered in stripes of thin epoxy/good varnish; thick epoxy/cheap varnish, thin epoxy/cheap varnish...
These coating tests take years to carry out. Will The Plug survive to see all others fail? Will it be there when apes rule the earth? Does the answer lie in citric acid residue?