Today’s topic is widely misunderstood even within the Nordic industry – we’re going to talk about “Black waxes”. What conditions are they good for? What are the differences between them? Ask 50 different shops and you’re likely to get 50 different answers. In that light, we’re going to dig in and discuss not only the answers to those questions, but also the underlying reasoning behind those answers.
To begin with, we need to know what black waxes are and what makes them different from other waxes. Black waxes contain one or more extreme pressure lubricants such as Graphite or Molybdenum Disulfide (commonly called “moly”), which have a crystalline structure that consists of several sheets connected by very weak chemical bonds. This unique structure gives these compounds three important characteristics: they shear easily, are very hard and correspondingly durable, and they are very good at dispersing static charge.
As we discussed on day three, a ski’s speed is limited by a combination of true friction effects commonly referred to as “dry” friction and adhesion with water commonly referred to as “wet” friction. Dry friction itself can be broken down into two parts: the force it takes to shear off snow crystals that have penetrated the base and the additional energy it takes to break any static attraction that may have formed between the wax and the snow. It is also important to note that impurities in the snow such as dirt or salt can be much more difficult to shear off and may also be much more or less electronegative (i.e. able to generate a static charge) than snow crystals, which is why these impurities will almost always cause slower conditions.
The idea behind black waxes, then, is to provide a durable layer which snow crystals and impurities cannot easily penetrate, to reduce the required shear force anywhere they do penetrate, and to prevent as much static buildup as possible along the ski base. These safeguards come at a cost, however – the lubricant cannot achieve the same water repellency effects as the hydrocarbon and fluorocarbon chains used in standard waxes and can, in certain conditions, increase the adhesion with the snow.
Due to their unique characteristics, the general rule is to use black waxes when the snow is dirty or, occasionally, when it is very dry. Because they can punish you in a way that standard waxes can’t, we recommend using them with caution – when in doubt, go without. That said, we’ve seen pure black waxes win wax tests, so owning and using them when appropriate is absolutely essential to getting the fastest skis for all conditions.
As a final note, a commonly asked question relating to black waxes is “What is the difference between Graphite and Moly?” In terms of wax applications, there is surprisingly little information available, but our own wax testing as well as the small amount of research that has been published have both indicated that graphite acts better than moly as an antistatic but can attract some particles and does not shear as easily. From a performance perspective, this means that graphite works better in cold conditions, while moly works better in warmer and very dirty conditions.
-Posted by Josh Doebbert on Jan 22nd 2014