Cold snow is slow because the snow crystals are sharp and there is very little liquid water to lubricate them. It is very similar to skiing across tiny pieces of broken glass. As snow ages and gets warmer, the crystals become more rounded and the snow pack contains liquid water that serves as a lubricant. Imagine this as skiing across microscopic marbles with some oil on them.
Base Prep
When it is cold, the abrasive snow creates two problems: friction and durability. There are also some electrical issues that arise out of spinning the snow crystals, but we’re going to ignore those for now since friction is the dominant problem. The goal of base prep is to make the ski as flat and featureless as possible to reduce drag against those sharp crystals. That means either stone grinding the ski specifically for cold with a grind such as our ZR1, or using a metal scraper to peel the base. A peeled base is only good for extremely cold snow - use only a sharp metal scraper, and at your peril. A metal scraper in untrained hands is quick to ruin skis. Practice on a pair of rock skis first. Once you have a smooth base, finish by brushing with a soft metal brush followed with a polishing Fibertex, which combs the microscopic base "hairs" down.
Waxing
Next, iron in several layers of cold glide wax. Any remnants of warmer wax will slow the ski significantly, as the sharp snow crystals will penetrate the wax and grab on to it. Multiple layers of cold wax are needed to harden the base up and cover any remnants of softer waxes. The good news is this stuff is cheap. The bad news is that it is a pain to apply. Good choices are Start Green, Swix CH4 and Toko Blue. Cold Powders add hardness and should be sprinkled in with the above waxes when snow is especially fresh, dry and cold. We like Toko Cold Powder, SkiGo C380, Swix LF3 and Solda S30 as hardening waxes to deal with extreme cold.
Cold wax is very hard in order to prevent those sharp crystals from penetrating the ski base and also to give the wax extra durability. In order to achieve this hardness, the wax is made of a synthetic compound that has a melting point approaching that of the ski base itself. So, with a quality wax iron, carefully apply several layers of cold wax. Mom’s old clothes iron is not the best choice because it probably does not have a precise thermometer, and will therefore fluctuate as much as 50ºC. This is dangerous when you need to heat the wax within 10-20ºC of the base’s melting point.
The iron should be just hot enough to melt the wax quickly. For those who are ignoring the advice about quality wax irons – that is probably somewhere between permanent press and linen, when the smoke turns deep black. Drip or grate the wax onto the ski and melt it into the base, moving the iron very quickly in multiple passes. Each pass should take no longer than 10 seconds. Test for overheating with your hand – if it is too hot to touch, give it a rest.
The wax is melted adequately once it has a smooth appearance and there is no evidence of the original drips. Let it cool to room temperature, but before it gets too brittle, remove as much as possible with a sharp plastic scraper. You may want eye protection for this step.
Finishing
Now the important part: brushing. Take a soft metal brush like a medium bronze or fine steel and brush until your arms cry for mercy. Then brush for five more minutes. The goal is to polish the base to a glass smooth finish so nothing drags on that abrasive snow. Be cautious with roto-brushes, as they can burn bases if used improperly.
With skis brushed to a shiny polish, place them out in the cold for 15-30 minutes (or longer), or better yet, ski on them for ~2km. This will contract the pores in the ski base and squeeze out additional wax. Then, lucky you, brush again and again and again. The more you brush, the faster your skis will be. This can make a 30% difference in ski speed.
Kick Wax
If you are classical skiing, you will need extra durability for your kick wax due to the abrasive snow. Begin with a clean kick zone after you have finished glide waxing. Rough the kick zone with 100-grit sandpaper, then apply a thick layer of cold kick wax. Using a torch, heat gun, or iron, melt this layer into the base and let it cool. After corking smooth, apply and cork many thin layers of the final choice of kick wax. Avoid getting glide wax in your kick zone when ironing or brushing, as it will greatly reduce durability and kick. Race Service people use masking tape or duct tape to cover the kick zones.