Salmon

Salmon* – 1) Common Name for several fish in the Salmonidae family, including trout. 2) A range of a pale pinkish-orange to light pink colors, named after the color of salmon flesh. 3) A highly fluorinated racing wax named for its color.

There was another big ski race this weekend, the City of Lakes Jr. and Minne Loppet.  All three boys raced and had a great time.  Two of the three pairs of skis had super fast salmon ski wax.   I’ve written previously about ski wax and I continue to be intrigued by the wax material itself and the discipline of selecting and applying wax to skis.

My previous description of wax covered the “sticky” type called kick wax. Salmon is of the other type and engineered to help the skier glide on the snow surface. The principle of glide wax is to balance the wet friction, or suction, of liquefied snow and the dry friction, or roughness, of the snow crystals. The goal is to get the ski to melt a thin layer of liquid water to reduce the dry friction without creating too much of a puddle for the ski to suction to.

Like kick waxes, specific glide waxes are designed to perform under a variety of conditions. In general hard waxes are for cold conditions and soft waxes are for warmer conditions.  Wax is a lipid which means it is in a category of molecules that are mostly composed of long hydrocarbon chains.  Ski wax softness is determined by the length of the hydrocarbon chains in the wax molecular whereas the length of the chain determines the softness of the wax, with longer chains producing a harder wax.

If you’ve made it this far in the post you may be wondering, “Why does he keep going on and on about wax?”  To which I’d say that I’m just fascinated by it and it demonstrates how science permeates our lives.  So I’ll continue.

One of the big innovations in wax is the addition of fluorocarbons.  You may have noted from the definition that opened this post that Salmon is a highly fluorinated wax.  Fluorocarbons have some interesting properties, including that some formulations can dissolve such high concentrations of oxygen that you could actually “breathe” their liquid form. This is an interesting topic but the property that makes them useful for inclusion in ski wax is that they can repel both oil and water.  By “highly fluorinating” ski wax the wax engineers created a product that performs like a wax without getting dirty and therefore glide better and make the ski faster.

OK, now you know why I wouldn’t stop gushing about wax: it proves that science is awesome.

Later, I’ll continue the wax story by outlining the art and science achieved by wax technicians who not only leverage the surface chemistry of the wax but also manipulate the surface geometry to maximize the ski’s effectiveness.

*Special thanks to Wikipedia for supplying inspiration for the wording of the first 2 definitions.

Wax

To cross country ski is to live a paradox. The skier must glide frictionless on the snow but has to stick to the snow in order to propel forward. To do this the skier has to rely on one thing- wax. A classic ski has two types of wax, glide and kick.  Glide wax is applied to the length of the ski and provides a nearly frictionless surface that allows the ski to slide across the snow. Kick wax is applied to the “kick zone”.

The kick zone is below the foot and somewhat variable but generally extends several inches in front of the toe and just behind the heel. Kick wax is a bit more interesting than glide wax because, like the kick zone, it is variable.  Different kick wax is used based on the temperature. The general idea behind kick wax is that it lets the ski stick to the snow. However the way it works is a bit different. The wax actually allows the snow to stick to the wax. 

Snow has a crystal structure that makes it rather rough at the microscopic level.  The rough snow surface grabs onto the corresponding rough surface of the wax and allows the skier to push, or kick forward. If the wax actually stuck to the snow it would be disastrous for the skier because snow would build up on the bottom of the kick zone and reduce the ability to glide. This actually happens when the wax applied to the ski isn’t matched to the size of the snow crystals on the trail.  

Fortunately skiers don’t have to carry specialized equipment to the trail in order to gauge the microscopic magnitude of the ice. All they need is a thermometer.  How does a thermometer predict the size of snow? The answer is the same answer that makes all of science work.  The natural world is predictable.

Snow crystal size is dependent on temperature just like the descent of an apple to Earth as it falls from a tree is predicted by the force of gravity. Science has exposed countless predictable phenomena and relies on this predictability to explain new observations, make predictions about yet unobserved events and even helps skiers stick and glide on snow.