Kick & Glide
Regarding Leonid Kuzmin's Thesis: Are Unwaxed Skies Faster?
By Ian Harvey
Editor's Note: In 2005, Leonin Kuzmin, a professor in the Department of Applied Physics and Mechanical Engineering at the Lulea University of Technology in Sweden, published a thesis that has created a buzz across the snow belt. The 72-page thesis, "Investigation of the Most Essential Factors Influencing Ski Glide," raised eyebrows by questioning the need for waxing Nordic skis. Despite wax manufacturers' investment of millions of dollars in technical advancements, Kuzmin calls their findings pseudoscience. Decades of waxing experience in international caliber competitive events fails to convince Kuzmin of the benefits of waxing. He presents his findings by identifying and refuting three "e;Mantras"e; he believes are promoted by the ski industry. The thesis can be viewed at this link: http://epubl.ltu.se/1402-1757/2006/03/LTU-LIC-0603-SE.pdf.
Ian Harvey, TOKO USA brand manager and former United States Ski team member, has written our Kick & Glide column for five years. In this expanded column, Harvey addresses Kuzmin's findings.
National teams devote a great deal of money to ski structure and wax testing to ensure their skis are the fastest. Elite Nordic racers always wax their skis, with one exception-when the snow is exceptionally dirty and greasy. Only in the most polluted snow do skis glide faster if they have never been waxed. But contrary to elite racer results, Leonid Kuzmin argues that unwaxed skis are faster across the board.
Kuzmin says that the ski industry adheres to Mantra number 1: The ski base is porous, and we have to melt in glide waxes many times to impregnate the ski base.
He argues that ski bases do not become impregnated with wax. He reasons that a hydrocarbon wax molecule is larger than a water molecule, which begs the question, why haven't we seen water enter a ski base? However, you can measure with a thermoanalyzer exactly how much wax enters a base. By slicing off 1/1000 millimeter pieces, we can even see how deep the wax has penetrated. This is how Toko came up with measuring the effectiveness of ironing waxes-temperature versus time-as well as comparing the effectiveness of ironing versus treating skis with a Toko Thermo Bag. To quantify how much wax enters a ski base, others arrived at the same conclusion by weighing a ski before and after waxing.
So, why don't we see water entering a ski base? If you were to heat up a ski base and then pour hot water on it, a small amount of water would enter the ski base...only to be squeezed out when the base cooled off and contracted. Kuzmin ignores the need for heat to expand the base. But after preparing skis inside a warm room for very cold conditions, skiers notice outside that the bases turn "white"-the cold contracted the base, pushing the wax out. Contrary to wax, water does not get solid enough to be retained by the base and effectively become part of it.
Kuzmin attacks Mantra number 2: It is very important to use glide waxes to protect the ski base from abrasive wear.
He disagrees. He posits that glide waxes do not protect a ski base from abrasion because a ski base is harder and more resistant than ski wax...therefore, treating a ski base with wax only makes the base less resistant to abrasion.
When we apply moisturizer to skin, it becomes more resistant to abrasion because the lubrication helps reduce the friction. The same with wood furniture and furniture polish. Softer treatments protect against abrasion as well as restore-another key function of ski wax. Like skin or furniture, dry skis are easily abraded or scratched.
Let's take a closer look at Kuzmin's methods. Sand slurry tests measure the abrasive effect on materials. You put Ptex and chunks of ski wax in a barrel mixed with coarse sand and water; after several hours, you evaluate the amount of abrasion on them. But Kuzmin never did the test; he just assumed that Ptex is many more times abrasion-resistant than any ski wax on the market. Based on this assumption, he concluded that glide wax acting as a base protectant is absurd.
When we apply blue wax to a base, scraping and brushing it out, the base is far harder than with yellow wax. Why? Because blue wax is hard and brittle-even harder and more brittle than a graphite base. Introducing this hardness to the ski base makes it more resistant to dry friction that abrades and slows the ski.
Kuzmin attacks what he calls the ski industry's Mantra number 3: Graphite ski bases are much more advantageous than skis with a transparent base.
He argues that transparent base material is faster and better than black base material. (He refers to it as graphite base which is how it is commonly known; however, black bases do not contain graphite, but carbon or soot). Using a chart from the Ptex manufacturer IMS Kunststoff AG, he shows the wax absorption of bases to point out that black bases are inferior to clear bases.
However, except for very wet snow, black bases run better than transparent bases. Of course, transparent bases are better for promotion because graphics show on ski bottoms, creating cool looks and great exposure.
Ski manufacturers such as Atomic and Germina used to make transparent-based (6000T) skis specifically for very wet snow-a very limited market. When ordering base material from suppliers, ski manufacturers must order it in miles of material-eliminating base material limited to specific snow conditions simply because of cost effectiveness. But Kuzmin sums up, "Why ski makers only produce X-C skis with a graphite base is one of the biggest mysteries in the ski business."
After attacking what he calls the three ski industry mantras, Kuzmin then turns historian. Disdainful of wax companies, he criticizes the foundation and evolution of Swix, ignoring a number of pre-Swix wax companies. He describes how pathetic the waxes were in the mid 1940s-an era known as the second generation waxes, in which skiers used the same wax for both kick and glide, although a softer wax was sometimes applied on the ski middle. Claiming that nothing revolutionary has happened with kick waxes over the past 60 years, he equates the current kick waxes with the old glide waxes.
In 1940, Toko marketed the very popular hydrocarbon 1-3-5 glide wax-a harder wax for cold (1), a medium wax for around freezing (3) and a softer wax for warm (5). While the paraffin was not as pure and lacked synthetic additives, it was similar to today's hydrocarbon glide waxes, but nothing like kick waxes: Resembling candle wax, they were slippery, not sticky. As a testament to simplicity and function, the 1-3-5 evolved into Toko's blue, red and yellow today. While kick wax for colder and easier-to-wax for conditions hasn't seen a revolution, recent decades have improved binders and the dirt resistance of klisters and silver hard waxes.
Summing up his wax history, Kuzmin attacks a third generation of waxes-fluorocarbons and perfluorocarbons. He says they are hardly radical, but rather a promotional gimmick. But results bear witness: To race in wet snow without a perfluorocarbon overlay is to resign one's self to a poor performance.
Kuzmin questions why skiers stopped using kick wax along the ski's full length in favor of glide wax on the tips and tails. He attributes some of the reason to alpine companies-Kneissl and Fischer-that produced the first plastic skis. But skiers stopped using kick wax along the ski's full length because glide wax on the ends and kick wax in the middle worked better.
In two supporting papers, "Contact Angles on the Running Surfaces of Cross Country Skis" and "Dirt Absorption on the Ski Running Surfaces--Quantification and Influence on the Gliding Ability," Kuzmin expands his hypothesis that waxing has no benefits, arguing that skis don't accept wax after stone grinding. Kuzmin accuses the stone grinding machine makers and wax companies of snookering the cross country ski market to pile up money, since stone grinding requires follow up with a "very material- and labour-intensive" process. But ironically, stone grinding was an instant success where it mattered most-in the elite racing field. After all, it makes a base ready to absorb tons of wax. No "convincing" was needed. National teams flew all over the world to get ground by some of the early grinding masters. As the art developed, many of the national team waxers became grinding experts out of necessity. I estimate that 95% of all 1992 Olympics ski medalists (Alpine, Combined, Jumping, Biathlon, and Cross Country) won on skis ground specifically for the Olympic races two weeks prior. With today's improved technology, a skier can race the next day on a clean stone grind followed by proper waxing.
Accusing stone grinders of limiting options to longitudinal patterns, Kuzmin suggests cold temperatures require a transverse (lateral) structure instead. But in cold temperatures, skis require minimal structure. Cold powder is one of the only conditions where the horizontal structure makes a dramatic difference. Back in 1989, I played with structure in my own ski bases: I filed a transverse (45-degree diagonal criss-cross) structure on my ski just to verify my intuition that it would slow the skis. It did.
He also contrasts stone grinding results with steel scraping, a process he feels produces a more hydrophobic ski. However, hydrophobicity is measured by analyzing the angles at which a water drop sits on the base surface. His metal-generated hairs contributed to the water angle resulting in a high measurement whereas the stone grind results in no "assistance" to the water drop angle. Concerned with long-term pollution absorption, Kuzmin also addresses dirt-pointing out that minimizing grime improves glide. By steel scraping and applying different glide waxes, he treated several skis with a transparent base and a white background--to test the gliding ability of waxed and unwaxed skis, the sliding surface whiteness and the hydrophobicity. At different distances, he tested hydrophobicity, observing that all waxed skis-regardless of wax type-absorbed more dirt than unwaxed. His conclusion? All waxed skis lost their glide ability sooner than unwaxed, dry skis.
Assuming he tested in rare extreme dirty snow, he was dead right on. As skiers discovered in the filthy snows at the 1995 World Championships in Thunder Bay, Ontario, brand new unwaxed skis stayed cleaner and thus faster longer. Because most dirty snow is trucked in from airports and fishing docks, it's loaded with oil and other pollutants. Of course, a dirty greasy base will be less hydrophobic than a clean base. Without wax, dirt and grease have nothing to cling to, making a faster base.
For some tests, Kuzmin used a Steel Red Creek rotobrush-a brush intended for alpine skis requiring more structure and glide for much higher speeds than Nordic. Based on this, his test results are questionable.
While Kuzmin argues that unwaxed skis are faster across the board, elite racers prove otherwise. Technique, speed and stamina are tools the athletes bring to the race, but all those being equal, waxing takes their skis to the top of the points lists.
© Cross Country Skier: October 2006, Vol. 26 Issue 1