Features July 15, 1999 Issue

Sticky Business: Duct Tape Tested

Duct tape may look alike, but it varies in longevity, strength, and user-friendliness. Of the nine tested, we like Manco, 3M and National.

There’s probably not a handyman (or woman) in existence who hasn’t had experience with duct tape. The universal holder-together, duct tape has been used to make temporary repairs in the house, the car, around the yard, on NASA missions (where it’s standard equipment) and, always, aboard boats. It serves as makeshift chafing gear (or to hold chafing gear on the line), seals hatches during storms (we’ve done it), and, in the case of medical emergencies, can be used to cover cuts and set bones. Duct tape has even been used to seal heating and venting ducts, although several recent studies say it’s not very good at that. In our thorough Practical Sailor tradition, it was decided to see if duct tape lived up to its reputation in other areas.

A Little History
The modern relative of duct tape, from most reports, was invented by the U.S. Army (remember this fact), purportedly to mend rents in tents and seal ammunition boxes.

Originally olive drab in color, the tape was a combination of cellulose laminate-covered cloth and a rubber adhesive. After the war, someone had the idea of using it to seal ducts, hence the name that has stuck; the color has changed to gray or silver, but it’s also available in various other colors. Today, the laminate is as likely to be polyethylene film as cloth, although the adhesive is still rubber-based. It comes in a variety of grades from economy to household to contractor, and so on. There is a UL standard (181B) governing pressure-sensitive tapes, including duct tape, used for sealing flexible heating, ventilation, and air-conditioning ducts—still the mainstay of the $75 million a year industry. The standard (we reviewed the summary on a UL website) covers such things as tensile strength, peel adhesive and shear adhesive strength, and resistance to fungi—but there's no specification for longevity.

On the shelf, all duct tape looks pretty much alike—silvery, usually measuring 2 inches by 10 yards, and is fairly close in price. Which doesn’t mean it’s fairly close in performance, although tape that is somewhat elastic may be better at one job, while one that adheres well may be better at another task.

Nor are the manufacturers especially forthcoming with the consumer—virtually no information about materials and specs are printed on the product. We decided to test various brands of tape to determine how similar—and dissimilar—they actually are in use.

The Brands
We scoured around hardware, department and marine stores (plus a few discount outlets) for some of the better known brands and largely succeeded, although no Tuck-brand duct tape could be found, except for some moldy relics at a surplus shop; nor could we find any samples of Nashua brand, also purported to be popular. Easily obtained were several grades from 3M (the brand carried by most marine stores), several from United (aka Tesa), and some of the popular hardware names, including Servi-Star and Ace. We got some Manco, which like Ace, likes to call theirs “Duck Tape” and added an Anchor roll, because it sounded appropriately nautical (and also claimed to be “strong, durable, and weatherproof.”) That’s the kind of specific claim that cries out to be put to the test. In all, nine different duct tapes were tested.

Because many uses for duct tape are likely to expose the tape to air, sun and water, strips were placed on a fiberglass hatch and left out in the early summer sun and rain. We kept an eye on how long they adhered, how easily they peeled off after exposure, and how much residue they left behind. Noted was how easy they were to use, whether they could be torn by hand or shredded, and how elastic they were.

Tensile strength also was tested (it’s not clear how relevant this is, but it’s something that could be tested). Because a broken hose at sea can be a nuisance or an immediate danger, a test was devised using air pressure to see how well duct tape could stem the flow of water under pressure.

The Results
At the risk of insulting an American institution, it appears that duct tape isn’t very good at many of the tasks asked of it. With few exceptions, it was found that it broke down quickly in the weather (but then we knew that from having to rewrap our chafing gear regularly), won’t adhere to anything outdoors for long, although it will leave a sticky mess behind, and can’t hold back liquid under pressure very well at all. It can be fairly strong, depending on the brand, but, again, there are not too many uses for that quality, unless it’s jury-rigging a (very) temporary repair to a sail or broken piece of gear.

There also have been a number of government-funded studies recently that declared duct tape inferior compared to virtually any other kind of pressure-sensitive tape for sealing ducts. For one thing, it’s extremely sensitive to heat, and its longevity is suspect.

The Exposure Test
For each brand, 18-inch strips of tape were attached to a fiberglass hatch with both molded nonskid and smooth surfaces. Each was overlapped an inch or two at each end, and smoothed down so that it was firmly adhered. We checked the strips periodically but waited 40 days to take our first notes. There were some noticeable differences, with some tapes still fairly in place, some beginning to wrinkle up, and others with some serious curling or lifting at the edges and/or ends.

Best of the bunch, at this point, were the Manco Duck, with very minor lifting at edges and no wrinkles, and the two 3Ms (Home & Shop and High-Performance) doing well also, especially the High-Performance brand. Absolute worst was the Anchor (“strong, durable, weatherproof”), which had virtually disappeared, the laminate apparently vaporized (or was consumed by fungi). Also not so hot were the United Standard Grade, which showed severe curling and lifting, and the Servi-Star Professional Grade, which wasn’t wrinkled but was showing considerable lifting at the edges.

In the middle: The United Contractor’s Grade, which had little lifting but some delamination at one end, the National General Purpose, which had severe wrinkling and some lifting at one edge, and the Ace Duck.

Two weeks later, the situation had progressed fairly evenly for the most part, but none was in what you’d consider especially good shape. The Manco stripped off easily but had curled much at the edges. The two 3Ms came off laminate first, followed by the underlying threads, which retained their structure; the United Contractor’s Grade was similar, but it’s economical cousin, the standard grade, left a lot of adhesive residue behind when the strip was pulled off. The National came off fairly easily and stayed intact. No need to remove the Anchor, whose few remaining shreds of thread crumbled like the contents of a pharaoh’s tomb.

Tensile Strength
Breaking strength, probably, is related to both the fabric—the density and quality of the threads that make up the cloth—and the strength (and elasticity) of the laminate that backs it. We won’t claim that our methods here were particularly scientific or accurate to within an ounce or two, but each tape was subjected to multiple (just ask our lower back) pulling tests, measured carefully with a 50-pound fish scale, and the results averaged.

What we did was overlap the strips by two inches on the edge of the hatch, while laying down about 10 inches across the hatch. (We quickly learned that it takes virtually no pulling to strip off duct tape, fresh or old—one of its pluses, we’d guess).

While many of the tapes tore easily—a virtue on a rolling boat—we remembered noting how “difficult” the National General Purpose tape was, refusing to tear, curling over on itself, and generally annoying the usually objective tester. We used either a knife or a scissors to complete the job. Well, surprise. While some of the other tapes snapped at as low as 23 pounds of pull, the National finally broke at about 50 pounds, stretching to some degree first.

We grudgingly grant that, if nothing else, it’s very strong—as well as elastic. Average breaking strength in our tests was about 31 pounds.

Hose Test
It didn’t take us long to find out that duct tape isn’t much good for plugging leaks. Employing several bicycle inner tubes (with 5/32” holes) and a 260 psi 12-volt air compressor, we found that air began leaking out the sides of the tape (several wraps, including some overlap) at under 10 psi. In that sense, it wasn’t so much the tape as the seal (or adhesive) that failed. We let the compressor run anyway to see if we could force a bubble or burst the tape(s), but when the inner tube began to resemble a python who’d recently snacked on a VW, we desisted, not so much in the interest of science as in self preservation. (We recently saw notice of a product called Speedseal that is specifically designed to temporarily patch leaks in water and fuel hoses and can take up to 100 psi.)

Duct tape serves well for many temporary repair jobs, but excels at none. While there’s little difference in price, there are some distinct differences in performance. We liked the Manco for its staying power, and the 3M High-Performance for its general ease of use, strength, and longevity. And, while it’s a bear to work with, the National General Purpose (fairly inexpensive at $1.49 for 10 yards) is both strong and durable.

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