Hot boxing: What it will do. What it won't do.

Many skiers like to have their skis saturated with glide wax using the “hot box” method. This has led to a lot of misunderstanding about what it does for the skis and the skier.

Hot boxing began as a way to speed up the saturation process on new skis, and increase the absorption of glide wax after a routine waxing. Early experimenters believed that keeping the skis warm for a while after regular iron-in waxing made more wax go into the base material. Extended, gentle warming does seem to help saturate new bases more quickly than applying dozens of coats of ironed-in wax. That's the beginning and end of it right there. You might also like to do it at the beginning or end of a season to refresh wax in the base, but the procedure is most useful to put a quick charge into new bases that have not been waxed at all.

Hot boxing is not a wax job to last you all season. You will need to iron on some glide wax after skiing a few times. Because your skis have been initially saturated, they will absorb and retain wax better than skis that have only had meager coats of wax at long intervals, but you still need to renew the surface. Cold, hard conditions are abrasive. Warmer, moist conditions often bring debris to the surface, which is also abrasive.

Hot boxing is only worth it on a high performance base. Performance skis have sintered bases. Sintered bases are made by pressing particles of base material into a layer in a sort of dry process, compared to extruding the plastic in a liquid or semi-liquid form. Extruded bases do not have the porous structure that sintered bases do. The pores are what hold the wax. Ski wax is more than just a polish. This isn't your kitchen floor, or your car.

Not all sintered bases are created equal. Cheaper racing skis, and many touring skis, use high-density sintered bases. These will not retain wax as well as lower-density base, but their microporous structure appears to interact better with the adhesives used in ski construction, making them somewhat more resistant to delamination than skis using extruded bases. Some of you may have experienced the tragic loss of a good old Trak or Karhu ski because the base material peeled off. Those companies used extruded bases because that technique was the best for producing the beloved Omnitrak waxless pattern. But plastic is notoriously hard to glue. Smooth plastic presents the greatest challenge to long-term adhesion. While high-density sintered bases are not immune to delamination, the material appears to give the glues a better grip. This is purely a field observation, unsupported by any kind of formal experimental proof.

If you do decide to iron a glide wax on a high-density sintered base, understand that you will have to re-wax at least as frequently as someone lovingly caring for a higher-end racing ski. The harder base material is more resistant to abuse, but also to hot wax.

Cheap skate skis will have higher density bases than more expensive skis will have.

Smear-on wax is not your friend. Almost no one likes to wax. If someone invented a magic wand that you could wave over the ski base to leave it perfectly waxed, skiers would say, “Awwww! Do we actually have to WAVE it?” Many skiers seem willing to believe that the smear-on potions made for extruded and high-density bases are good enough to get by with on their performance skis. Not only are smear-ons inadequate for more than a minute or two, they will actually leave residues that inhibit the absorption of ironed-in wax. Interestingly, super-expensive fluoro racing waxes in all forms will also leave residues in the base material that need to be cleaned out with expensive special fluoro remover so that you, the performance addict, can properly iron in some wax to nourish the inner structure of the base material.

Damaged bases will not absorb wax. Bases are most commonly damaged by using too hot an iron. A hot enough iron will fuse the sintered material, sealing the surface so that melted wax cannot soak in. If the damage isn't too deep, it can be scraped away using various methods, from razor scrapers, wire brushes, and abrasive pads like Fibertex, all the way up to a stone grind. Portions of the base can also be sort of mashed flat if you have skied them dry, or with too soft a wax, over very hard conditions. This damage can also be opened up again with brushes, scrapers, or Fibertex. This is more likely on a high-end ski with a low-density base. Low density bases are designed not only with plenty of porosity to absorb wax, but with the idea that a performance skier will want to imprint temporary structure into the base to deal with warmer, wetter conditions. The base material in its naked state is noticeably softer than on a ski designed to withstand neglect and abuse. And, as mentioned above, smear-ons and fluoros in general will fill the base pores with sludge. Expensive sludge, but sludge, nonetheless.

That white stuff isn't necessarily oxidation. Whiteness on a black ski base is commonly identified as “oxidation.” This is true often enough, as skiers neglect proper waxing, but even a careful and diligent waxer will see some whitened areas at times. Abrasive conditions can roughen an area, and cold conditions can cause wax to squeeze out of the base pores as the material contracts. Waxing guides mention that the skis should be cooled to air temperature and brushed out a few times as excess wax comes to the surface. Before hitting the panic button and insisting that your skis have been inadequately waxed, hit them with the horsehair brush for about ten strokes and see if the color improves. After a while you will develop the ability to look at the base after brushing to determine whether the whiteness was really oxidation. And of course you can never go wrong by waxing your skis one more time. But a good brushing may save you the trouble.

A note about skin skis: In the past couple of years, skin grip inserts – formerly known as mohair – have made a comeback. They first reappeared on classical racing skis to cover a temperature range and snow conditions in which kick waxing was basically impossible. “Zero” skis address the narrow heart of that range, but mohair offers a wider effective range. Now most companies offer mohair bases on multiple touring models as well.

Mohair was fairly common in the 1970s. It's the same material as climbing skins. As a grip base, it is held in with temperature-sensitive glue, similar to what is used to hold grips and baskets on poles. It is purposely intended to come off with the application of heat, so that worn out inserts can be easily replaced. This is generally not much warmer than the hot box temperature, so hot boxing of skin-base skis is not recommended. You need to be careful enough just ironing around a hair insert because you don't want melted wax to flow into the hair.