FLUOROCARBON
"INVISIBLE" LINES
Editor Nick Caine and Key-Chem's Laboratory Manager, Steve Adams, take a look at some of these so-called "invisible lines".

"INVISIBLE" FLUOROCARBON MONOFILAMENT FISHING LINES 
Monofilament fluorocarbon fishing lines have been available for several years now, and their main claim to fame is that they're nearly invisible in water — but have they matched up to their claims and met anglers' expectations? Here we take a critical look at three of the better-known brands:-

Technical Information
Fluorocarbon monofilament lines are made from an artificial polymer, poly-vinylidene fluoride, or PVDF for short! Normal nylon monofils have a higher refractive index (1.5) than that of water (1.3), so when they are submerged they are more visible than PVDF monofils which have a lower refractive index (1.4) that's closer to that of water itself. Well, that's all very nice in theory, but how do these PVDF monofils actually perform in practice?

Well, PVDF monofils may be less visible to fish but of course fish can also detect under-water objects with their ultra-sensitive lateral-line sensory system. For this reason we feel that the best applications for these nearly-invisible lines are on the surface and on the bottom of clear-water venues, especially ones that are heavily-fished and where your quarry are very line-shy.

Good for Clear Waters
This makes these fluorocarbon lines potentially very suitable for fly-fishing leaders and for specimen hook-lengths for carp, barbel, bream, chub and tench and this has been borne-out, for example, by the fact that Ashima's Poltergeist fluorocarbon leader-line has taken the UK fly-fishing market by storm — its progress in the coarse fishing sector has been a lot less meteoric though.

These nearly-invisible PVDF lines were first developed to fulfill the demands of Japanese anglers fishing in very heavily-fished areas where the fish are ultra-cautious and line-shy. In Japan the benefits of these fluoro-monos out-weigh their extra cost, line and knot breakage and other brickbats, but in other countries and applications, their margin of advantage may not be quite so large or nearly so cost-results-effective!

Higher Density
These fluoro-monos also have other properties that are different from normal nylon monos and this means that you have to adjust your technique slightly. Firstly, fluoro-monos have a much higher density, with a Specific Gravity of 1.78 compared with 1.15 for nylon and 1.00 for water. This means that for the same length of the same diameter line, fluoro-monos are considerably heavier than nylon monos. This means that they have a higher casting momentum and you have to take this into account when fishing!  For example, you may even have to step-up to a slightly beefier rod in order to be able to cope and cast the heavier fluoro-lines. Because of their higher density, fluoro-monos are also faster-sinking than their lower-density nylon counter-part monos.

Also, in certain fishing applications, especially those with multiplier reels, the higher density, greater weight and momentum of these fluoro-monos mean that you have to adjust the anti-over-run drag setting to compensate. 

Knots are Critical
Fluoro-monos are water-resistant unlike many monos, so they don't lose their strength after prolonged immersion in water: as a result they have much less elongation (stretch) under load. Also, provided that, and it's a very important proviso indeed, fluoro-monos are very well lubricated as you tie the knot, they have excellent wet-knot-strength. The type of knot that you use is very critical with PVDF monos: always follow the manufacturer's instructions to the letter. 

Don't use an over-hand knot with fluoro-monos! Our tests have shown that the Palomar knot is one of the best and there's also the Trilene knot, developed by Berkley: needless to say, they strongly recommend its use for their own PVDF fluoro-mono, Vanish. We also strongly recommend the use of a good line lubricant before pulling your knots tight: Sufix's Rod Hutchinson Slick Horizon line-lube is one of our favourites. This will ensure that a good knot-strength is maintained.

Abrasion Resistance
Fluoro-monos are dense and tough and, although the manufacturers claim that this gives them good abrasion resistance, we've not found this to be the case for the fluoro-monos that we've had tested by our professional laboratory. If it's good abrasion resistance that you really need, then we suggest that you choose a non-fluorocarbon mono — have a look at our other Top Tackle Tests on Monos.  

Also, inevitably, there are some other disadvantages to these tough, dense, low-stretch fluoro-monos, and these come in the form of greater stiffness and a greater tendency to form coils i.e. greater "memory" and lower suppleness. In fact we have to say that our On-the-Bank Tackle Test Team were quite disappointed with these disadvantages.

Low Stretch, Greater Sensitivity
Their density, toughness and water-resistance mean that fluoro-monos have low stretch and therefore greater sensitivity and this greatly improves bite-detection and hooking-rates. They also have a high resistance to shock-loads. 

Accurate Diameters and Strength
Key-Chem's laboratory technicians have checked the actual and claimed diameters of the fluoro-monos that we've been using and have found that the claimed diameters are very accurate and that for all the samples, line diameters were very consistent throughout the length of the spool. For example Ashima's claimed diameter for their 10 lb BS Poltergeist fluoro-mono is 0.28 mm and Berkley claim a diameter of 0.41 mm diameter for their 20 lb Vanish fluoro-monos and the tests carried-out by their lab technicians confirmed that these claims are absolutely accurate!

Resistant to Degradation
Their higher density, toughness and water-resistance and the fact that these fluorocarbon PVDF polymer lines are inert means that they are not degraded or weakened by UV light or many oils and other chemicals. This means that they maintain their strength much longer than other monos.

And what's more, the professional laboratory tests that we've had carried-out at Key-Chem Products, confirm that these fluoro-monos do indeed maintain their strength during what are known as "Accelerated Weatherometer Tests" which expose the lines under test to high levels of moisture, oxygen, temperature and UV light, equivalent to 2-years' tropical use!

*Relum and their top-drawer supplier of lines, Sufix, are no strangers to professional tackle testing and their products (and those from their competitors!) are always very rigorously tested to ensure top-notch quality and compliance with their performance claims. Relum have been marketing Sufix's fluorocarbon line, Invisiline, for some while: in fact it was probably one of the first major fluoro-monos on the UK market. Invisiline is made from Mitsubishi's high-purity, high-integrity poly-vinylidene fluoride polymer and like *Ashima's Poltergeist fluoro-mono, has found favour as leader-line among the UK's fly-anglers and as specialised hook-length-line for carp and other wary coarse species. (*Note: Both Relum & Ashima have now ceased trading in fishing tackle in the UK, sadly)

Recent Entrant
Another fairly recent fluoro-monofil entrant to the UK fishing scene as a result of the global mergers and acquisitions of Berkley and Abu Garcia to form the Pure Fishing Group, is Berkley's Vanish and we've been giving this line some very thorough testing too. Suffice to say that we found that it met its claims and diameters very accurately. Apart from the comparative cost, we found that, like the other fluoro-monos in our tests, it works well in clear-water conditions but does suffer from "memory" and slightly higher stiffness than we would like, but this is a small price to pay for better catches in hard-fished clear-water conditions such as fly-fishing venues.  

Cost Comparisons
The saying goes that you can never get something extra for nothing and that's true for fluoro-monos with all their advantages that we have outlined in this Review: they are more expensive than traditional nylon monofils and some of the latest 4th generation monos that are on the market. 

Compared with the Recommended Retail Prices, the actual prices that you pay for lines vary enormously but as a rough guide, fluorocarbon monos tend to cost between 50% and 80% more than conventional nylon monos but gel-spun high-density polyethylene braids can cost 400% or 500% more than nylon monos!

SUMMARY
Although there's an accompanying price penalty, there's no doubt that PVDF fluorocarbon monos do offer substantial advantages over traditional nylon monos especially for some specific applications such as fly-fishing leaders and hook-length lines in heavily-pressured clear-water conditions where their lower visibility counts and the fish are very line-shy.

With the right knots, fluoro-monos also have good knot-strength, and, because of their low stretch properties, good sensitivity . We have experienced some inexplicable line breakages and knot failures with larger lures, and so we cannot recommend these fluorocarbon lines for such applications — stick to braids or hi-tech monos!

Thumbs Down ?
And in coloured-water conditions, we reckon also that, compared with some of the other modern 4th generation high-tech monos and braids available, these attributes of fluorocarbon monos only marginally justify their higher cost and that there's little point in using them as main lines except in clear, very heavily-fished waters.
Nick Caine & Steve Adams

Please click the Key-Chem logo button below
to go back to our Home Page