Q: I have been told that in the "old days," the breaking strength of fishing line was determined by the line's physical thickness. As it was explained to me, regardless of the monofilament manufacturer, if the line's diameter was X, then its breaking strength was Z. I guess the practice of determining breaking strength by thickness made sense, but with today's technologies, this practice seems outdated. Is it true that manufacturers still determine a line's classification by using an archaic formula based on its diameter?
I ask this question because I discovered a major inconsistency between a line's "stated strength" and its "actual breaking strength" on a spool of 6-pound test mono I recently purchased. In order to make sure I was maximizing my drag settings, I decided to check the actual breaking strength on my new spool of line. After several tests, I discovered that the average breaking strength of my spool of 6-pound was right around 11 pounds! How/why do monofilament manufactures misidentify the breaking strength of their products, and if I want 6-pound test line, should I look for a spool that says 4-pound on it? - Scott Ingerto
A: Your supposition is partly true! In the good old days, you could at least get a hint as to the breaking strain of a monofilament nylon line from measuring its diameter. But today, slight differences in chemical composition (there are now several different nylon molecular structures) make a difference. And the actual process of "drawing" the line at different speeds and at different oven temperatures also changed not only the breaking strain, but also knot strength, abrasion resistance and stretch in any given diameter of mono.
Nowadays manufacturers can label a line as 1-pound test (based on diameter) but prominently display a 4-pound test measurement on the label as well. This means that the line is guaranteed to test over 4 pounds with a hook tied on with a palomar knot. That same line on the spool might break anywhere from 11 to 16 pounds! Which is incredible line, but very confusing for the angler who wants to know exactly where his line should break.
I need to know first and foremost how strong my line really is, and the only way I can do that is to test it myself. (Luckily I have access to a couple of good, expensive line testers.) You can also become a member of the IGFA and send them samples of your line to test.
Dacron line usually tests close to what is shown on the label. Superbraids, made from gel-spun polyethylene, never test right, and monofilament nylon sometimes tests right if it says IGFA class line somewhere on the label. Even then, however, the IGFA label is not a guarantee it will test at the right breaking strain; it's just telling you that the manufacturer is attempting to make the line break just under the IGFA kilogram rating for that line.
So if you really want to know at what pound test your line will break, test it yourself.
