What the Base Does for Glide:
The base materials of Nordic skis, as well as all other types of skis and snowboards, are designed to mitigate the affects of friction. All of the base materials used are made from Ultra High Molecular Weight polyethylene (UHMW), which happens to be a close cousin of the of the opaque milk jug. The bases material is also made from number two High Density Poly Ethylene (HDPE). The difference between the milk jugs and skis is that the ski bases use much longer chains of ethylenes. Base manufacturers will form the bases by compressing a powder form of polyethylene and using heat. The bases will have molecular weights between three million and six million. Anything greater than six million will not have the pore space to accomadate waxes. The manufacturers also add colorants and additives to the resin powder in order to give the bases different properties. Common additives are carbon black, graphite, and fluorocarbon powders. What really helps with the gliding proccess is the low surface energy of the polyethylene. The low surface energy makes the base hydrophopic so that it can repel water. The importance of this is the effect on the coefficients of kinetic friction. A water wet base has approximately half of the fricition of a dry base. As skis glide across the snow, there is a thin layer of water due to fricitional heat, and so, the more hydrophobic the base is, then the lower to coefficient of kinetic friction, which in turn makes for a better glide. The approximate coefficient of kinetic friction for ski base is in the range of 0.03-0.05.