Heatbox and Hardening the Bases of Cross Country Skis
In keeping with the fact that my strengths are with knowing what works and how to do it properly, in preparation for the writing this article I consulted with a few people whose advice I trust and who are good with the technical explanations.
There are varying opinions with regards to the use of Heatbox and Hardening the bases of skis. The information presented below represents my beliefs on these topics.
Heatbox and Hardening the Bases of Skis
The purpose of using a Heatbox is get a soft wax saturated into the bases of skis. After I stone ground skis, I put the skis in the heatbox for a minimum of 8 hours. The intent is to get wax into the base of the skis. The other way to get a soft wax in the base of the skis is to use an iron. Both ways work.
To harden the bases of skis, I am now using Star Polar Next Glide. This wax is an excellent wax. It is faster than the previous hard green waxes that I have used in the past, easier to scrape and polish and it is an excellent base for other waxes, in particular, liquids.
After the bases of the skis have been allowed to cool, I scrape off the soft wax and then pass the skis though a waxing roller which has Star Polar Next Glide. Using an iron temperature of 150 C’, I pass the iron over the base of the ski, let cool and then pass the iron over the ski a second time. After the skis have been allowed to cool, I leave the wax on the skis OR scrape and polish the bases of the skis demanding on what the customer wants. For high performance situations, I repeat this process a second time. After the skis have been scraped, well brushed and polished, I pass the skis through the waxing roller with the Star Polar Next Glide. I pass the iron over the base of the, let cool, a second pass of the iron, let cool, scrape, brush, polish.
The process of ironing in a hard wax into the bases of ski accomplishes 2 main things. It gets a hard wax into the base of the skis and it hardens the bases. Some people call it hardening, other searing the bases and others state tempering the base of the skis. One thing for sure is that surface layer of the base is changed. If you take a cabinet scraper with a sharp edge, and remove a thin layer of the base of the that has been hardened and thin layer of the base of a ski that has not been hardened, by using a magnifying glass, you can see a difference. As best I can describe it, the edges of the cells of the base are fuzzier/more rounded than the cells of the base that have not been hardened.
When the bases of the skis are saturated by using a Heatbox, the wax penetrates deeper into
the base than hard wax when using a iron. The soft wax acts as an anchor for the hard wax. As a result of the mixing of the soft and hard waxes when ironing in the hard wax, the hard wax is drawn further into the base of the ski. As a result, there is more hard wax in the base and therefore the wax lasts longer. This is the main advantage of getting a soft wax into the bases of skis before applying the hard wax compared with just applying the hard wax. On a few occasions, I have ironed in the hard wax on a skis that has not been saturated with a soft wax. I do not like the feel of the iron when doing this. The iron drags more than when ironing in the hard wax in which the base has been saturated with the soft wax. I am not willing to harden the bases of skis unless the bases have been saturated with a soft wax.
When hardening the bases of skis, the hard wax is mixed with the soft wax. Conservatively, there is 10 time more of the hard wax on the surface of the ski than the soft wax the base. After 2 passes of the iron, the wax in the base may well be 90% hard wax. When this wax is scraped off and re-waxed with Star Polar, after 2 passes of the iron, the amount of soft wax in base of skis may well be less than 1%. This in one of reasons why I do the hardening process twice. The other reason is that the ironing, scraping and brushing help make the bases extremely smooth. When this entire process is done properly, the bases are hardened and the bases have a hard wax that is close to 100% hard wax. There are no hairs on the bases of the skis, the structure in the base is not altered and the core of the ski is not damaged.
It always made sense to me that hard wax in the base of a ski would bode well in cold conditions. Having said, I learned more than 30 years ago that hardening the base works for skis in wet conditions. This past spring, the conditions for the long distance skate race at the Nationals were soft and wet. I waxed and hardened the bases of some skate skis to the best of my abilities. I was informed afterwards that these skis were fast.
It is my understanding that certain situations when there is moisture and a lot of dirt/pollution and when using high fluoro powders, the skis can be faster if there is no wax in the base of the skis. I have been informed that high level skiers in Europe will put aside certain skis that they intend to use in wet/dirty conditions. These skis are not waxed. Ideally these skis are stone just before the race, and in the aftermath the skis need to be re-ground. For skiers who race in Canada, if you can afford to put aside skis that only want/need to use once every 2 or 3 years at best, go for it. How you will go about the waxing/grinding/ re grinding is something that you will need to figure out for yourself.
In summary, if the process for base saturation and hardening of the bases is done properly, the skis will be faster. If you have not yet had yours skis prepared the way I have described above, I recommend that you try it, Having said this, unless you have a high quality iron, the right tools and experience with ironing hard waxes, I recommend that you get someone who is experienced with this to wax your skis for you.