In this blog I take a look at a fantastic trout line.

The Amplitude Trout Fly Line (WF – Floating line).

SA's Amplitude Trout line
SA’s Amplitude Trout fly line

I suggest that before reading this blog you start with my previous one “Why do floating fly lines – float?”

Three colors

The running line is called celestial blue. The belly part is bamboo colored, and finally the front taper is blue heron. My eyes say grey, but I can go with blue heron too, because it is grey. Initially, I did not like these Harlequin lines, but now I love them. I find it advantageous to know how much line I am carrying, and with the coloring scheme, it is so easy. These colors also help, when I am teaching casters. Many of them tend to slip out line as they are false casting, and thus exceed their carry limit (all casters have a limit as to how much they can carry of line (keep in the air)). Most intermediate casters can carry 40′, and I use the end of the belly to remind them of the position. Casting with too much overhang (running line outside the tip top) is hard for beginners, but if they practice, they can carry more and more line, because they can keep the backcast straight. The front taper or grey part is about 12′ and the leader is 9′. Being cognizant of these lengths helps to pinpoint where the tackle is.

The core is braided multifilament nylon. The filaments are solid Nylon, but braided together to make strands (16 strands). The way they are braided yields a hollow braid. Each strand of yarn has a small amount of air trapped in it when coated, but most of the air in the core is in the hollow center, see previous blog. The line is not painted after being made. The PVC used to coat the core has a blue – then bamboo colored – then grey pigment, and the micro-balloons, added into the PVC coating mix. This coating transitions from one color into the other seamlessly. How that is done, I haven’t a clue, so we all can be glad that I am not the one doing that. The SG of the PVC coating of the level tip is nowadays 0.85. On top of all that the gray part has more air trapped in the mix (see later).

The line has seven red boxes with some hieroglyphs on the website. I will decipher them as we go. On the website there is some text under each box, but much too small for reading. Probably put there by the elves making these lines.

Amplitude Trout

Two types of texture

1. The Shooting Texture

Shooting Texture Icon
The Shooting Texture

After the coating is applied it is time to texture/emboss the line. The running line is textured/embossed with what SA calls, “Shooting Texture.” Textured lines have less contact with the rod guides, so they shoot better for more distance when needed. The texturing also increases the surface area of the line for better floatability. This texture is not rough on the fingers, but the rear taper is not textured to give a tactile reference point (see later). Then the Belly of the line is textured with the same “Shooting Texture” to the front taper. Shooting texture helps, you guessed it, in shooting the line, and it increases the floatability a little bit, too.

Shooting Texture
The Shooting Texture

2. The Floating Texture

After the coating is applied it is time to texture/emboss the line. The front taper and the level terminal tip are textured with the so-called “Floating Texture,” and that is an ingenious engineering application of the so-called “Lotus effect.” – – Now, an engineer at SA applied this knowledge to the surface of a fly line called Sharkskin in 2007. The natural hydrophobicity of PVC was kicked up several notches, and the line floated higher. Although the Sharkskin line shot great and floated high, the surface is rough on the fingers, so now the texture is limited to the front taper, and terminal level tip, and it increases that part’s floatation. This part of the line is not handled much.

I will repeat this. The line is textured/embossed with two different types of etchings. Seriously, this a job for dwarves. “Floating texture” helps, you guessed it, in floating the line, but its cast-ability is immaterial as this part is almost always outside the tip-top.

Floating Texture Icon
The Floating Texture
Floating Texture
The Floating Texture

Improved dry tip

Dry Tip Icon
The Improved Dry Tip

The crucial part of any floating line is the floatability of the tip. By increasing the amount of trapped air in the tip section (the gray part), the SG can be brought down to 0.80. This will float the tip higher. The tip floats because of manipulations of the SG, and by manipulating the surface into becoming hyper-hydrophobic. This is really hard core engineering.


AST Plus Icon
The AST plus +

The AST (Advanced Shooting Technology), was introduced 1998, and now all quality lines have this feature. A SA engineer came up with this incredible idea, in principe, a self lubricating fly line. AST means that silicone is incorporated into the coating mix. Then as time goes by, it leaches out onto the line’s surface. Such a line is much slicker than a line without this feature, and casts much better since the friction in the rod guides is diminished. AST then became AST+ after some chemical sorcery – making the line slicker.

Line identification

The ID

On the front taper the line ID is printed. I really like this feature, but with time the print wears off my lines. Therefore, I mark the weight of all my lines at the end of the running lines. A long black dash – 1” mark means five. A half inch dash means one. I read from left to right — —– becomes 4, —– — becomes 6, —– —– is ten (like the Roman system). This is quickly done and does not wear off. This is a really helpful little trick when you have many lines.

#7 - #8 - #10 Lines (from above)
#7 – #8 – #10 Lines (from above)

Welded loops

Welded Loops Icon
The Welded Loops

I really like welded back loops on all my fly lines. These back loops easily last the lifetime of the line. I like front welded loops on lines from #5 and bigger. On the smaller lines the loop is just clumsy. The fly line loop adds more floatation, but the butt loop connection adds more nylon (SG 1.2), making it an even game, so the flotation is not an issue. However, the front loop is somewhat ephemeral, and will fall apart some day. There is no getting around this one – you need a strategy to connect your leader to the line, without the easy fix of looping them together.

Tactile reference point

TRP Icon
The Tactile Reference Point

Part of the rear taper of the line is smooth, i.e. there is no shooting texture, and you can feel that. It supposedly helps to identify how much of the line is out. But that does not excite me since the colors are already there. When I used this line in Iceland last fall is was so bloody cold that I could just about feel the line, the tactile reference point was not felt.

Cost and quality

Fly anglers can become very excited, bordering on agitated, about their fly rods, and then have no clue about their fly lines. As I gain experience teaching casting, I am now in the camp that maintains that the fly line is the most important part of a fly angler’s setup. I like everything about this fly line. For dry fly trout angling it is fantastic. For salmon, when you are using small flies, it is superb. Furthermore, it is true to the AFTMA weight standards, i.e. a seven-weight line is exactly 185 grains. The front taper is twelve-foot long, so if I were to use very heavy flies, I would switch to the Anadro line, with its much shorter and powerful front taper. When you go through the points above, you realize that there is some serious engineering behind this line. SA maintains that this line is very durable (at the very least double lifetime or much more), and will last without loosing its characteristics. I have not owned one long enough to know that. However, the quality of this line is second to none.

I do not much like lines that are made stiff, hence coliy, or the so called tropical lines. It is just my peccadillo and I am the one living in this body. I left the Amplitude Trout and Anadro lines out in the heat (90 F) here in the Florida Panhandle. After that they were a tad limp, but when I still could cast the whole line, I can see no reason to have tropical lines in my arsenal anymore. Saves a bundle right there.

This line retails for $129.95. Is that prohibitively expensive? That is up to debate, and each of us might reach different conclusions. If the line lasts as claimed, its price is suddenly very attractive, for instance. Whatever your take is on the price, there is no better line in its class.

English consultant: My good retired neighbor Joe

Technical consultant: Bruce Richards

They shouldn’t!

A floating fly line is made of a braided nylon core, onto which PVC is added as a coating. The specific gravity (SG) of nylon is 1.2 and the SG of PVC is 1.4. With those numbers the line should sink. So, why does it float? (For perspective; Aluminum has SG of 2.7 and marble for instance has SG of 2.6)

Specific Gravity / Relative Density

SG over 1 – denser than water (sinks), conversely SG less than 1 – less dense than water (floats). Here is a simple review –

The level terminal tip – the critical part

When you are dry fly fishing you need a fly line that floats. Now that was an intelligent sentence. We like to turn over the leader gently, and that means a thin tip. If the line tip sinks, it will pull the leader butt under. Conversely, if the leader butt pulls the line tip under, it sinks. The line’s tip SG is ~ .85 (see later), it wants to float and will, unless something makes it sink. The leader has a SG of 1.2, and once under water, the whole leader system will drown, taking the fly under. The critical (to floating) part of the fly line is the level terminal tip. It is easy to make sure that the thick belly of the line will float like a cork. However, the fly line tapers and ends in 6” of level tip. Now the diameter of the tip is 0.037” and the relative contribution of the coating is much smaller than in the belly part.

The Level Tip's and the Belly's diameters
The Level Tip’s and the Belly’s diameters of Amplitude Trout

The Core and the PVC

The core is braided multifilament nylon. In between the filaments, which are braided into hollow strands, there will be some air, and the coating traps some air around the braid in the manufacturing process, which is the big contributor of air, bringing the SG of that part to just under 1.0, but not much. In 1954 SA added air bubbles to the PVC coating, and lo and behold — the new line floated. This is considered to be the first modern fly line. Subsequently in 1959, SA introduced micro-balloons into the PVC coating. The SG of the PVC coating of the level tip is nowadays 0.85. So, that takes care of the SG problem.


Any body placed in water will displace a certain volume (remember Archimedes?). Archimedes’ principle 


states that the upward buoyant force, exerted on a body immersed in a fluid, is equal to the weight of the fluid that the body displaces. So, now the line weight is less than the weight of fluid displaced, and the line floats. The SG is a reflection of Archimedes’ principle in relation to water’s SG set as one.

Surface tension

Surface tension ( is the tendency of liquid surfaces to shrink into the least surface area possible. We all have been shown iron needles floating in water, because of the surface tension.

Water’s surface tension is high. The PVC on the other hand is hydrophobic. By certain chemical additions (don’t know which – probably secret) to the lines’ surface, the hydrophobicity of the PVC can be increased. The silicone that leaches out of the line increases the hydrophobicity of the line, increasing the floatation, too. We can also apply silicone to our lines with good effect. We all know that cleaning our lines makes them shoot better and float better. A dirty line is just less hydrophobic – so now go clean your lines and buff them with silicone.


We know that a small piece with a bigger surface area will float better, because of the surface tension. The line’s surface area can in fact be increased by texturing. This is very similar to the dimples on golf balls. So, the surface area in contact with water is increased, and the textured line will now float higher.

Shooting Texture
Shooting Texture

The “Lotus effect” – Scientist have noticed raindrops falling on lotus leaves, and then just roll off. It turns out that the surface of lotus leaves are hyper-hydrophobic. The reason is that on the surface of the lotus leaves there are microscopic pointy structures, replicated millions of times. Engineers can mimic that effect by manufacturing lines with a rough surface (Sharkskin was the first in 2007). This surface is rough on the fingers. However, the hydrophobicity of the line can definitely be effected by manipulating the line’s surface.

Floating Texture
Floating Texture

Simply put, floating lines are lighter than water, and are hydrophobic, so they sit higher on the surface than they would if hydrophilic. Lines can be made hydrophobic chemically and/or mechanically.


Saltwater has a specific gravity of 1,024, so it is denser than freshwater. This allows us to construct a floating fly line for the salt, which can have denser coatings (thus thinner). SW lines’ slightly denser coatings make them tougher (PVC is weakened by most additives), and a bit thinner, which improves casting, i.e. less wind resistance.

Stóra Laxá 2020
Stóra Laxá 2020

To wrap it up

Shape of line and leader

Before we leave the floating line we need to look at shape. I have owned lines (and you, too) that look like a “slinky” when they come off the reel. It is a floater all right, but in this configuration it will sink. The part of the line that is above the water will push the bottom of the coils under. Once a line is subsurface it no longer has the benefit of flotation by being hydrophobic, now it is repelling water in all directions, not just from the bottom.

Line with coils
Coiled line

So, STRETCH your fly lines before you start using them. The same must obviously apply to your leader, so stretch that too while you are at it.

The line leader connection

If the water surface is calm, it is easy to get leaders to float, but we rarely have that luxury. Chop/turbulence causes parts of the leader to sink, and it is not coming back up due to its SG (1.2). It’s easy to float a 6X tippet leader (0.005”), not as easy to float a .030” tippet.  For best floating performance, it is very important that the leader especially the butt, is stretched straight (same reason as for fly line). Then dress with silicone line dressing. Remember, there is no silicone leaching out of the leader, and there is no texturing magic there.

The line/leader connection is important too. For lines with very little tip flotation (2-3 wt.) use a 2-turn needle knot to connect leader butts. Heavier lines have more tip flotation, so there are more options. Then there are anglers who use a 7 to 9-turn nail knots “gooped” up with lots of adhesive to make them stronger. These knots sink like a rock, and once the knot is submerged, the whole enchilada sinks. Remember, adhesives can’t make nail knots stronger, they are compression knots. If tied “neat” and pulled completely tight (rare), nail knots can be VERY strong. When the tip end-loop is clipped off delicate lines (I prefer that), it does expose the hollow core of the line, and a bit of water can wick in. Some anglers put a small drop of some sort of waterproof adhesive on the cut end (careful re SG), and that works for a while. Properly tied nail knots (meaning, pulled completely tight) will prevent water from entering too. But even if water does get in it won’t wick far and casting the line tries to force the water out, therefore it shouldn’t become a big issue.

Finally, pay attention to the material you are using. To recap — nylon has a SG of 1.2, but fluorocarbon has a SG of 1.8. Therefore don’t use Fluorocarbon with dry flies, and expect it to float.

English consultant: My good retired neighbor Joe

Technical consultant: Bruce Richards