Over the past few years, anglers have seen a new revolution in the production of fishing lines. We have seen the massive introduction of “super” lines, fusion lines, fluorocarbon lines, and hybrid lines to the shelves of our local sports stores, as replacements for the old stand-by we had gotten used to. Now a stroll through the fishing line isle is enough to get your head spinning as you glance through the brands, types and strengths. For fly fisherman, the choices are narrowed a bit for leader and tippet materials, but options still remain. This month’s article will focus on two of the most common options: nylon monofilament and fluorocarbon.

Fly fishermen may have a distinct advantage when it comes to knowing the difference between these two options, as they have had both materials readily available for leader material for quite some time. But, how many really know the differences that separate these two lines in the fishing world? This is where a little research pays off, and I have stepped in to help you shorten the learning curve. There are a few items that I will pay particular attention to in comparing these two line types: water absorption, underwater visibility, sink rate, durability and the ability to withstand the elements. Before I reveal the results of a number of comparison tests, let me first describe how each of these line types are made.

Nylon Monofilament

Nylon monofilament line is exactly what the name says: a single strand (“mono-filament”) of nylon, produced by passing a glob of molten plastic, actually a by-product of crude oil processing, through a die that creates the thin strand of nylon that we know as fishing line. Simple process, simple line.

Fluorocarbon

A more complex and expensive process is used in the creation of fluorocarbon line, in which a polymer of fluorine is actually bonded to carbon at a molecular level. The process is much more scientific than I care to understand or dive into, but the results are quite amazing.

Now that you have a basic grasp of how these two lines are formed, I will list below the differences that each process delivers, and how they can make fishing more productive with the right choice.

Water Absorption

If you are like me, you never realized that your fishing line actually absorbs water while you are fishing. In fact, this is a very important attribute that you must take into account when choosing a line. Standard nylon monofilament line will absorb a great deal of water when fishing. This causes the line to become heavier when wet, decreasing cast length and smoothness, and lowers the line’s breaking strength by about 20 percent after only an hour in the water. This means that a 10-pound test mono line will actually break with closer to 8 pounds of pressure when it is wet. I would guess that this absorption would cause far worse results in salt water, but was not able to find any brine-related tests. Fluorocarbon line on the other hand has zero water absorption because of its dense chemical structure. In theory, this means that fluorocarbon lines lose none of their strength, even when submerged in water for a number of hours. Further, by eliminating the additional weight of water in your line, you should be able to cast with greater accuracy and softer presentation with a fluorocarbon line.

Underwater Visibility

The main reason current anglers use “clear” lines is that they are much harder for fish to see than the rope lines of the past. This is another area where the fluorocarbon lines have far surpassed monofilaments. The factor that is used to determine a line’s visibility under water is its refractive index (RI), a measure of the amount of light refraction a certain substance has. This being said, it is easy to deduce that the closer a line’s RI is to the RI of water, the more it will blend in with the surrounding water, making it nearly invisible. Standard mono lines have a refractive index as high as 1.62, compared to water’s RI of 1.33. 100 percent fluorocarbon lines have a refractive index of only 1.42, much closer to that of water. The result is a line that is much more transparent to the underwater creatures we seek. A more invisible line can often be the difference when fishing the super clear waters usually found along the coast and in Hill Country rivers. These findings could be the reason that tests have concluded a strike ratio that is between 4 and 5 times higher when using fluorocarbon lines! This could add dramatically to your day’s productivity.

Sink Rate

Another huge factor when fishing is the amount of time it takes for your line to sink into the strike zone. The faster your line sinks, the quicker you can get your bait in front of submerged fish. The rate of sink that a line has is determined by its specific gravity. This is the same concept used to determine if a fly line is floating (with a low specific gravity) or sinking (with a higher specific gravity). The same rule applies to leaders and tippets. Standard monofilament lines sink at a rate that is nearly 4 times slower than its fluorocarbon counterpart. This trait can be used to your advantage in a number of situations. If you are nymph fishing deep holes in a stream, a fluoro line will bring the fly into the deeper water much faster, so that it stays in the strike zone longer. Also, if you are using a floating line, you can get your fly a little deeper in the water without having to switch fly lines by simply tying a slightly longer fluorocarbon leader.

Durability

Line durability is another area where fluorocarbon line excels far above the competition. Because of the manufacturing process and materials used to create fluorocarbon lines, they have an added feature that is very important to fisherman. These lines have an extremely hard and abrasion resistant outer coating. This can mean the difference between fish and frustration when you are faced with underwater line killers like brush and shells. Most of us have probably pulled our mono tipped fly line out of the water to see a telltale curly-Q hanging off of our line. Most likely, the line has lightly grazed the edge of a razor sharp oyster shell or other underwater structure, shaving off a fine strand of the line. Using fluorocarbon line in place of the mono may have prevented you from having to tie on a new leader as you watch the redfish boil and fin in front of you. Another feature of fluorocarbon line is its limited stretch. Unlike highly elastic monofilament, fluoro lines stretch very little, resulting in greater sensitivity and more powerful hook sets.

Ability to Withstand the Elements

One of the harshest opponents of our fishing line is the sun. As we fish the flats or rivers on a beautiful sunny day, our line is constantly absorbing harmful ultraviolet radiation. Like our skin, there is only so much that a line can take before it begins to suffer. That is of course, if you are using monofilament lines. A number of tests have shown that over a relatively short period of time, a monofilament line can lose nearly 40 percent of its strength when exposed to UV light. With the sun blazing overhead, the heat will also quickly deteriorate a monofilament line. Fluorocarbon, on the other hand showed no mentionable decrease in strength, even after a thousand hours of direct UV exposure. That is an impressive finding. On the other extreme, cold weather can play a substantial role in destroying line as well. When temperatures fall below what most of us in South Texas find comfortable, there is a definite effect that can be seen in both fluorocarbon and monofilament lines, though much more severe in monofilament. As temperatures drop, both lines become harder and their knot strength weakens. The advantage once again goes to the fluorocarbon lines, becoming stiffer and weaker about 4 times slower than its monofilament cousin. This is something to keep in mind the next time you plan a cold water trip to Alaska or the far north.

Overall, I found that monofilament lines are a thing of the past for most practical anglers that have experienced the many benefits of the new generation fluorocarbon lines. There is one catch. Fluorocarbon lines cost quite a bit more than the old stand by, sometimes double the cost. My personal belief is that the added benefits are well worth the extra cost, especially when you consider the longevity a typical fluorocarbon line will yield. There are obviously those who disagree, as witnessed by the spools and spools of monofilament still on the shelf. One other option is out there for those who are still on the fence about changing to fluorocarbon, the hybrid line. There are a number of manufacturers who produce a monofilament line that is coated with fluorocarbon material. This eliminates some of the negative aspects of monofilament lines while capturing some benefits of fluorocarbon with a medium-sized price tag. The choices are numerous and there is an option out there suited for all of us. Field experimentation is the only way you will find what works best for you. Besides, it gives you another excuse to hit the water. Best of luck to all of you as you pursue your favorite catch.