Ski wax is a material applied to the bottom of snow runners, including skis, snowboards, and toboggans, to improve their coefficient of friction performance under varying snow conditions. The two main types of wax used on skis are glide waxes and grip waxes. They address kinetic friction—to be minimized with a glide wax—and static friction—to be achieved with a grip wax. Both types of wax are designed to be matched with the varying properties of snow, including crystal type and size, and moisture content of the snow surface, which vary with temperature and the temperature history of the snow. Glide wax is selected to minimize sliding friction for both alpine and cross-country skiing. Grip wax (also called "kick wax") provides on-snow traction for cross-country skiers, as they stride forward using classic technique. Modern plastic materials (e.g. high-modulus polyethylene and Teflon), used on ski bases, have excellent gliding properties on snow, which in many circumstances diminish the added value of a glide wax. Likewise, unidirectional textures (e.g. fish scale or micro-scale hairs) underfoot on cross-country skis can offer a practical substitute for grip wax, particularly in wet or icy snow conditions.
History
Johannes Scheffer in Argentoratensis Lapponiæ (History of Lapland) in 1673 gave what is probably the first recorded instruction for ski wax application He advised skiers to use pine tar pitch and rosin. Ski waxing was also documented in 1761. In 1733 the use of tar was described by Norwegian colonel Jens Henrik Emahusen. In the 1740s the Sami people’s use of resin and tallow under their skis is recorded in writing. Beginning around 1854, California gold rush miners held organized downhill ski races. They also discovered that ski bases, smeared with lubricants brewed from vegetable and/or animal compounds, increased speed. This led to some of the first commercial ski lubricants, such as Black Dope and Sierra Lighting; both were mainly composed of sperm oil, vegetable oil and pine pitch. However, some instead used paraffin candle wax that melted onto ski bases, and these worked better under colder conditions. Pine tar on wooden ski bases proved effective for using skis as transport over the centuries, because it fills the pores of the wood and creates a hydrophobic surface that minimizes suction from water in the snow, yet has sufficient roughness to allow traction for forward motion. In the 1920s and 30s, new varnishes were developed by European companies as season-long ski bases. A significant advance for cross country racing was the introduction of klister, for good traction in granular snow, especially in spring conditions; klister was invented and patented in 1913 by Peter Østbye. In the early 1940s Astra AB, a Swedish chemical company, advised by Olympic cross-country skier Martin Matsbo, started the development of petroleum-based waxes, using paraffin wax and other admixtures. By 1952, brands such as Toko, Swix, and Rex were providing an array of color-coded, temperature-tailored waxes. Later in the 20th century, researchers addressed the issue of water and impurities adhering to skis during spring conditions. This was done through the novel use of a surfactant that interacted with the wax matrix to repel water effectively, an innovation first introduced in 1974 by Hertel Wax. Terry Hertel also developed the first fluorocarbon product and the first spring-time wax that repels and makes the running surface slick for spring time alpine ski and snowboard. This technology was introduced to the market in 1986 by Hertel Wax. In 1990, Hertel filed for a U.S. patent on a "ski wax for use with sintered-base snow skis", containing paraffin, a hardener wax, roughly 1% per-fluoroether diol, and 2% SDS surfactant. In the 1990s, Swix chief chemist Leif Torgersen found a glide wax additive to repel pollen and other snow impurities—a problem with soft grip waxes during distance races—in the form of a fluorocarbon that could be ironed into the ski base. The solution was based on the work of Enrico Traverso at Enichem SpA, who had developed a fluorocarbon powder with a melting temperature just a few degrees below that of sintered polyethylene, patented in Italy as a "ski lubricant comprising paraffinic wax and hydrocarbon compounds containing a perfluorocarbon segment".
Science of sliding on snow
The ability of a ski or other runner to slide over snow depends on both the properties of the snow and the ski to result in an optimum amount of lubrication from melting the snow by friction with the ski—too little and the ski interacts with solid snow crystals, too much and capillary attraction of meltwater retards the ski.
Friction Before a ski can slide, it must overcome the maximum value static friction, F m a x = μ s F n {\displaystyle F_{max}=\mu _{\mathrm {s} }F_{n}\,} , for the ski/snow contact, where μ s {\displaystyle \mu _{\mathrm {s} }} is the coefficient of static friction and F n {\displaystyle F_{n}\,} is the normal force of the ski on snow. Kinetic (or dynamic) friction occurs when the ski is moving over the snow. The coefficient of kinetic friction, μ k {\displaystyle \mu _{\mathrm {k} }} , is less than the coefficient of static friction for both ice and snow. The force required for sliding on snow is the product of the coefficient of kinetic friction and the normal force: F k = μ k F n {\displaystyle F_{k}=\mu _{\mathrm {k} }F_{n}\,} . Both the static and kinetic coefficients of friction increase with colder snow temperatures (also true for ice).
Snow properties
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