Science of the Ski

Glide Wax

When most people think of preparing skis they think of waxing and while wax isn’t the most important part of the ski it still plays a vital role in determining how fast a skier can go. Flex and structure of skis are relatively hard to change and so wax becomes the tool that allows a skier to fine tune their skis to the current conditions.

What is Wax and How Does it Work?
Looking at a selection of ski waxes in a shop can make them seem like a very fancy and complicated technology, but the truth is they are not much different from an ordinary candle. A basic ski wax is made up of something called a paraffin. A paraffin is a molecule comprised of hydrogen and carbon atoms lined up in a row the length of this row determines the properties of the wax. Generally the longer the chain the harder the wax.  

Glide wax is applied to a ski base by melting the wax while it is on the base. To understand what happens here we must first understand how a ski base is made. The base is constructed out of something called polyethylene, which is essentially a very hard plastic. This plastic is ground up into a fine powder and pressed into the ski base in a process called sintering. Sintering creates many fine holes in the ski base. When the wax is melted it seeps into the ski base via these holes and dissolves into the polyethylene.

When a ski slides across the snow snow crystals dig into a layer of this wax, but, because of the molecular structure of the wax, this layer slides very easily on the layer of wax beneath it. This reduces the friction since the ski only has to break free from a layer of wax instead of the snow crystals. The softer the wax the easier it is too break free from. Unfortunately, if the wax is too soft and the snow crystals are sharp enough they will penetrate through many layers of wax and make it difficult for the wax to break free. The correct wax for the conditions will be hard enough to stop the snow crystals from penetrating too far, but no harder.

In addition to the basic hydrogen and carbon in a ski wax, certain additives can be included to give the wax beneficial properties.  

Fluorinated Wax
Fluorine is one of the most common additives to the basic paraffin molecule. In a fluorinated wax fluorine atoms are combined on the molecular scale with the hydrocarbon chain, replacing some of the hydrogen-carbon sets with fluorine-carbon sets. This process is very extensive and the reason fluorinated waxes are expensive. The combination of fluorine and carbon is very hydrophobic, meaning it repels water. As water touches a fluorinated wax its surface tension increases causing it to form a small ball and “attempt to get away” from the surface.

Hydrophobic properties are very useful when conditions are such that significant water films are created under the ski base. Because the ski base is repelled from the water capillary forces are reduced and it becomes very easy to slide the ski forward.  

Pure Fluoro Wax
Pure fluoro waxes, also called perfluorocarbons, consist of only carbon and fluorine atoms. These waxes are used primarily as a final layer of wax. They do not dissolve into the base and are repelled from hydrocarbons, so it is important for a fluorinated wax to be dissolved into the base before the pure fluoro is used, so that it can bond to the fluorinated portion of the wax. It takes hardly any energy for Perfluorocarbon layers to be separated and they are extremely hydrophobic, which makes them a very fast wax option.

Base Waxes
The primary purpose of a base wax is to reduce the buildup of electrical charge on the ski base. This reduces the electrostatic friction and reduces the amount of dirt build up on the base. Base wax additives are generally dry lubricants such as graphite, molybdenum disulfide and diamond like carbon. The process by which these materials lower the electrostatic charge is extremely complicated and I was unable to find much information on it. However it does have something to do with the interaction of the electric and magnetic fields of both the dry lubricants and the snow crystals.

Dirt resistance and durability are increased with these dry lubricants because they are extremely hard substances and make it difficult for dirt and snow crystals to penetrate and pull away or stick to the wax.