the snow. Too little melting and sharp edges of snow crystals or too much suction impede the passage of the ski. A tipping point between where crystal type dominates sliding friction and moisture content dominates occurs around . Harder waxes address colder, drier or more abrasive snow conditions, whereas softer waxes have a lower coefficient of friction, but abrade more readily. Wax formulations combine three types of wax to adjust coefficient of friction and durability. From hard to soft, they include synthetic waxes with 50 or more carbon atoms, microcrystalline waxes with 25 to 50 carbon atoms and paraffin waxes with 20 to 35 carbon atoms. Additives to such waxes include graphite, teflon, silicon, fluorocarbons, and molybdenum to improve glide and/or reduce dirt accumulation. Application Glide wax can be applied cold or hot. Cold applications include, rubbing hard wax like a crayon, applying a liquid wax or a spray wax. Hot applications of wax include the use of heat from an iron, infrared lamp, or a "hot box" oven. Base material The role of glide wax is to adapt and improve the friction properties of a ski base to the expected snow properties to be encountered on a spectrum from cold crystalline snow to saturated granular snow. Modern ski bases often are made from ultra-high-molecular-weight polyethylene (UHMWPE). Kuzmin asserts that UHMWPE is non-porous and can hold neither wax nor water, so there is no possibility for filling pores; furthermore, he asserts that UHMWPE is very hydrophobic, which means that wet snow does not appreciably retard the ski and that glide wax offers little additional ability to repel water. He notes that clear bases are more durable and hydrophobic than those with carbon content. The same author asserts that texture is more important than surface chemistry for creating the optimum balance between a running surface that's too dry (not slippery enough) and too wet (ski subject to suction forces). In warm, moist snow, texture can help break the retarding capillary attraction between the ski base and the snow. Giesbrecht agrees that low wetting angle of the ski base is key and also emphasizes the importance of the degree of surface roughness at the micrometre scale as a function of snow temperature—cold snow favoring a smoother surface and wetter, warmer snow favoring a textured surface. Some authors question the necessity to use any glide waxes on modern ski bases. Grip wax Cross-country