How does a line dressing work? If you are not interested, stop reading now.
You might wonder why putting a "floatant" or line "dressing" would help a fly line float. After all, the coating of a fly line is water proof so it cannot work by water proofing something that is already water proof.
Ever notice how water beads up on a car after it has been waxed? The wax does not waterproof the paint that is already waterproof. When water beads up, that water droplet is actually being repelled by forces at the molecular lever. The molecules in the line dressing are designed to repel the chemical "polar" or electrical forces that surround a water molecule.
This repulsive force can be measured by measuring can be measured by the "contact angle" of the water droplet.
The contact angle is the angle that a water droplet forms with the surface. The higher the contact angle, the greater the water repellency or hydrophobic property.
Here is a water droplet on a cloth treated with water repellant.
In the images above, the higher the water droplet is lifted above
the solid surface, the greater the water repellency. Now think of this process in reverse
with a solid fly line on the water surface.
This repulsion of the fly line dressing by the water prevents the line from penetrating the water surface. It is the principle of the contact angle in reverse.
Now you know how line dressing works to float the line.
What is in the future? I think this is the next big step.
So far floating line technology has worked by making the fly line float by using specific gravity; ie, the lower the line mass density, the higher it will float. I predict that the next step will be to design the line surface to also actively repels
water. Current modern line coatings self renew by leaching a slick coating to decrease line friction while casting. If that coating can be both slick and super hydrophobic, it would be a boon to floating fly lines. It keep the lines floating without having to treat them.