Fluorocarbon lines and leaders have been around for many years now, but it’s only since the bream-on-lures thing took off around Perth that there was a perceptible level of demand created here. The main reason, of course, is that very few people knew about the stuff.

A close second, as reasons go, was that the stuff used to be hideously expensive. What is commonly called fluorocarbon was invented about 25 years ago, by Kureha Chemical in Japan. They called it polyvinylidene fluoride, abbreviated to PVDF. Kureha, which market as Seaguar, remain the only PVDF manufacturer to handle every stage of manufacturing from the raw material through to spooled fishing line.

Although it wasn’t originally made as fishing line, a material that could be extruded something like nylon (it’s a much more expensive and complicated process), but that was less visible, harder wearing and could still tie knots, obviously had some potential. True fluorocarbon differs from nylon in that it doesn’t absorb water, and is said to be unaffected by sunlight. These features are touted as merits, but of course in practice don’t matter much, at least with leaders. Water absorption weakens nylon, but not enough to cause concern for most anglers. Sunlight does stuff nylon eventually, but we’re talking months in normal fishing situations, not hours. Visibility is probably the biggest thing. Fluorocarbon has a refractive index close to water’s, so some brands claim invisibility once the line is below the surface. Others claim 70 per cent less visible than nylon. The usual figures given for refractive index are 1.33 for water, 1.37-1.42 for fluorocarbons, and 1.52-1.62 for nylon.

The visibility thing has a question mark over it, according to my eyes. In a sink full of water, 0.50mm fluorocarbon seems to be just as visible as 0.50mm clear nylon. But the index of refraction is a proven thing, and we don’t know how a fish sees it anyway. Berkley tested the visibility or otherwise of fluorocarbon in a reasonably real-world way: they hung lengths of nylon and fluorocarbon in a big aquarium, and monitored how often the fish bumped into the lines. They agree that to human eyes, the fluorocarbon seems just as visible; but over a lengthy test time, the fish bumped into the fluorocarbon twice as often as they bumped into the nylon. There seems to be enough anecdotal evidence about to reinforce the scientific opinion that it is less visible. I have read, from trout fishermen, some very convincing side-by-side trials that would have anybody binning all their nylon – if it wasn’t for the cost. Is it worth it? Lots of trout fishermen, and more and more bream fishermen, think so. A lot of guides in US trout streams used to have it as a “last resort” secret weapon, when the fish are being so shy that something special is called for. Now it’s mainstream, if you’ll pardon the pun. Many trouties also like the fact that it sinks faster than nylon – it’s almost twice as dense.

At the opposite end of the spectrum, gun tuna anglers worldwide know that leader visibility can make a world of difference even to a fish weighing a hundred kilos or so, and there are times when you won’t get a bite on nylon leaders. As the story goes, when the first shipment of Kureha fluorocarbon arrived in the US in 1990, it was trialled by long-line tuna fishermen targeting yellowfin. The particular team set up 350 hooks with fluorocarbon, and left 350 hooks rigged with the usual nylon. The first set resulted in 44 tuna, 43 of which were on the fluorocarbon leaders. Still on visibility, something Ross Cusack put in The West Australian about 30 years ago always stuck in my mind. He was writing about the visibility or otherwise of wire, and made comment about how we’ve probably all seen photos of fish where the line is clearly visible in the photo, but the wire trace seems to disappear. Why is it so? Without getting into the physics of it, picture one of those lamps with the hundreds of bits of monofilament nylon hanging out of them; put some light in at the right angle, and the nylon fair lights up, to the point where it’s glowing. You can’t do that with fluorocarbon (or wire, obviously). You can’t use fluorocarbon for fibre optics either – it just doesn’t trap light like nylon does.

The density may be the reason most anglers perceive fluorocarbon to have better abrasion resistance than nylon. I’m no fan of machines that “test” abrasion resistance; in reality, diameter makes more difference than anything, I’m sure. But it is nice to be using a line or leader that you don’t think of as fragile. Peace of mind.

However keep in mind that this stuff, compared with nylon, really is heavy. Used as a main line, it will have some “suspending” lures sinking; using baby poppers can actually become difficult, because with a slow retrieve the lure can be dragged down. Adjustments to technique may need to be made. A lot of anglers also like the stiffness that true fluorocarbon exhibits, particularly those using it as a main line on baitcasters. Comparing diameters and breaking strains, fluorocarbon is about the same as nylon. Stretch is another factor. Fluorocarbon stretches around 20 per cent, give or take 4 per cent, before it breaks. Nylon is up in the high 20s-early 30s, so fluorocarbon is a little more “direct” when it comes to feeling taps and setting hooks; nowhere near as touchy as braid, but that’s not what everybody wants anyway. It’s the in-between line, between braid and nylon.

Many times in this I have referred to “true” fluorocarbon. Like “graphite” fishing rods, there are degrees. Blending other polymers can bring down the cost of “fluorocarbon” lines considerably, but you won’t be comparing apples with apples. If it seems cheap, it’s probably not the real thing. Kureha started out making one style of fluorocarbon monofilament, and it was only suitable for use as leader material. It was stiff – very stiff – and 27kg was the lightest rating. The material took off in the long-lining fisheries, and after a few years found its way into the recreational angling scene, but obviously with limited application. It was incredibly expensive back then.

As it became better known and more widely used, the price came down and the range increased. Kureha needed two years of development to successfully produce tapered fly leaders, which were warmly received, especially in the saltwater environment; the stiffness assisted the casting of bulky flies, and the low visibility was desirable. Now Kureha manufactures dozens of different formulae of fluorocarbon monofilaments, plus a variety of tapered fly leaders. As the availability graduated down into small diameters and the price became realistic, Kureha and other PVDF manufacturers came up with formulations that were pliable enough to be used to spool reels, not just be used as leaders. The formulations now available to us as main lines on reels are typically 100m lengths, in breaking strains from 1.4kg to 9kg, for around $20. Compared with nylon, it’s still expensive, but no longer prohibitive. Beyond 9kg, to be soft enough for casting, it can’t be pure fluorocarbon (yet). Kureha recommend no heavier than 5.5kg be used on spin reels, as the line is still relatively stiff and can cause casting problems beyond that size; but up to 9kg is okay on baitcasters and overheads. On reels, the main advantage is durability; for leaders, it’s either durability, or low visibility, or both, depending on the scenario. The stiffer leader material is still more durable than the softer reel line though, something the manufacturers are quite upfront about.

YGK’s Nitlon DFC is typical of the new castable fluorocarbons, for using as a main line on a reel. It’s pure fluorocarbon, features high abrasion resistance, and is available in 13 sizes from 3lb to 30lb. The hard leader material is fairly readily available in strains from a kilo or so (freshwater) through three and four kilos (bream) and 20kg (mulloway, snapper) on up to 60 kilos (sailfish, tuna) in spools of 50m or less.

We’ve seen some anglers shy away from fluorocarbon because they have problems with knots. They need to review their technique. The light stuff ties knots fine, but plenty of lubrication is essential; remember, it doesn’t absorb water at all, so it’s pretty easy to wipe water off it. In the heavier leader strains, crimping is advisable, and probably essential for 45kg and beyond. Fluorocarbon lines have been hailed as the most technologically-advanced lines of this decade, which is a big call when looking for an Oscar against a plethora of superbraids. But the more I see of fluorocarbon, the more I think the call is right. This is a product that has its place, and it’s only just being welcomed in now. It’s much more than just a “different” mono.

Most fluorocarbon leader material has always been manufactured in Japan, and YGK is a leading brand. It’s noticeably stiffer than even hard nylon, and in heavier strains must be crimped, not tied. As leader material it’s now about three times the price of an equivalent size in nylon, which is much less difference than a couple of years ago.

© Hal Harvey