How to Choose Skis with the Right Base – Part 2: What's Hiding in a Black Ski Base?
In Part 1, we explained why buying cross-country skis involves more than choosing a famous brand and beautiful graphics. We should pay particular attention to the actual ski base.
We also looked at extruded and sintered bases and the main types of polyethylene.
And we concluded that even expensive skis from a famous manufacturer aren't automatically a good purchase.
But perhaps you noticed something interesting.
Most high-quality cross-country skis have black bases.
Why?
Is black faster?
And if black is so wonderful, why do manufacturers also produce transparent and coloured bases?
The answer is a little more complicated than it might seem.
Because a ski base isn't always made from polyethylene alone. And neither its colour, the number of grooves nor a beautiful surface structure can guarantee good glide.
What Exactly Are Additives?
Additives are substances introduced into a base material to modify its properties.
In ski bases, they may influence:
- Mechanical strength and surface wear resistance.
- Electrical and thermal conductivity.
- Interactions between the base, snow and water.
- Material behaviour during manufacturing and surface preparation.
- Colour and resistance to ageing.
Some additives primarily serve technical purposes. Others may also be important for appearance or manufacturing.
And some can affect several properties at once.
That doesn't automatically mean every change will improve glide.
After all, adding more ingredients doesn't always make something better.
Especially when you're cooking.
Graphite: Why Are Ski Bases Black?
Carbon-based materials are among the best-known additives used in ski bases.
They include graphite and various forms of carbon particles, such as carbon black.
These materials can give polyethylene its black colour.
However, they are not chemically or structurally identical, and their effects can differ.
Graphite is known for its layered structure and the low shear resistance between its layers.
That is why it is used as a solid lubricant in many industrial applications.
But a ski base is not a solid block of graphite.
It is a polymer containing a particular amount of carbon-based additives.
And its behaviour depends on their type, concentration, distribution and the properties of the polyethylene itself.
Electrical Conductivity
Pure polyethylene is a very good electrical insulator.
Carbon-based additives can increase its electrical conductivity.
That is interesting when considering the possible generation and dissipation of electrostatic charge during contact with snow.
But we cannot simply conclude that more graphite always means better glide.
Electrical conductivity alone does not explain all the processes occurring at the ski–snow interface.
Thermal Conductivity
Carbon additives can also influence heat transfer.
This may matter during contact with snow, where mechanical and thermal processes take place alongside capillary and viscous effects under certain conditions.
However, higher thermal conductivity is not necessarily beneficial or harmful in every situation.
It depends on the particular ski–snow system, speed, temperature and actual contact conditions.
And What About Mechanical Properties?
Additives can modify hardness, toughness, wear resistance and other polymer properties.
But we should not automatically assume that adding graphite must soften the base.
The actual result depends on the formulation and manufacturing process.
For recreational skiers, the conclusion is fairly simple.
A black ski base can be excellent. But black colour alone does not guarantee excellent performance.
Transparent Bases: Are They Really Inferior?
No.
Or at least, not automatically.
Transparent bases may be extruded or sintered.
Some are inexpensive recreational materials, while others are highly specialised, high-quality bases.
A transparent appearance may reflect the absence of black carbon fillers, but it tells us little by itself about molecular weight, mechanical properties or actual glide performance.
That is why we cannot rely on a simple rule:
Black skis for warm snow.
White skis for cold snow.
Such a shortcut may occasionally reflect the intended use of certain racing models, but it certainly isn't a universal law.
What matters is the combination of material, ski construction, surface structure and snow conditions.
And above all, actual performance on snow.
When a Ski Base Becomes Advertising Space
Now we come to something about the ski industry that has always amused me a little.
Once manufacturers began using black ski bases, they lost the opportunity to display colourful advertising on the underside of their skis.
And what could possibly be better for a manufacturer than an athlete standing on the podium with a beautifully visible logo?
Unfortunately, athletes can occasionally be rather undisciplined.
Especially after crossing the finish line.
Not everyone remembers, in a moment of complete exhaustion, to turn their skis towards the cameras with the correct advertising side facing outwards.
And so we sometimes encounter skis with a base that is partly transparent and partly black.
The transparent material makes it possible to display colourful graphics on the underside of the ski as well.
I'm not suggesting that advertising is the only reason for every such design. A particular manufacturer may also have technical or production-related reasons.
Nevertheless, using the underside of a ski for advertising is certainly an interesting idea.
The manufacturer gains another visible surface.
But what does the paying customer gain?
That depends on the actual construction.
If different materials are joined directly within the glide zone, it's worth looking at the quality and geometry of the joint.
A step, unevenness or another surface defect could be undesirable for glide.
However, the mere presence of a transverse joint does not prove that a ski will perform poorly.
My personal preference is simple: Unless there is a good technical reason for a combined base, I prefer a continuous, properly finished glide surface.
After all, we can admire the advertising on the top of the ski.
On the bottom, I'd rather see something that actually glides well. 😀
One Groove or Three?
And now another feature that makes me slightly uneasy when looking at certain skis.
The number of longitudinal guide grooves.
Cross-country skis may use different designs, including one or several longitudinal grooves.
Personally, I prefer the simple solution with one groove.
And if someone introduces a design with three grooves, I'd like to know why.
Not because I'm fundamentally opposed to technical innovation.
Quite the opposite.
But in my opinion, every new technical solution should offer some verifiable benefit.
Longitudinal grooves may play a role in ski guidance, contact geometry and the behaviour of water at the ski–snow interface.
All of these are technically interesting questions.
But the benefits of multiple grooves depend on their shape, depth, position, ski construction and specific snow conditions.
So we cannot simply claim that three grooves will always be slower than one.
Nor can we claim that three must automatically be better.
In very wet snow, water management may matter. But this is also precisely where a suitable ski base structure comes into play.
And that structure can, to some extent, be adapted to changing snow conditions.
So my position is this: One properly designed groove seems like a perfectly reasonable solution. Why should I want three if nobody can explain their specific advantage?
Of course, if someone presented convincing comparative test results, I'd be happy to reconsider.
But the mere fact that three is more than one hasn't impressed me particularly much so far.
Machine-Produced Structure: A Good Servant but a Bad Master
And finally, one of my favourite subjects.
Ski base structuring.
We've already written a number of more technical articles about how surface structure affects ski glide.
And believe me, it's a much more fascinating topic than a few tiny grooves in black plastic might suggest.
A properly produced structure can have a significant effect on glide, particularly when it matches snow characteristics and temperature conditions.
Modern grinding machines can create fine, coarse, linear, chevron-shaped and interrupted structures.
Their capabilities are remarkable.
And in the hands of an experienced professional, they can deliver excellent results.
But here comes my favourite word.
But.
Not every structure that looks technically impressive will perform well across a wide range of conditions.
Deep, pronounced structures may be advantageous on certain types of wet snow.
In other conditions, however, they may be less suitable than finer structures.
So the problem isn't that machine structuring is bad.
The problem arises when we have a highly specialised structure on skis we intend to use in almost every kind of weather.
Especially when we're talking about children's skis.
Are we really going to buy our children several pairs of cross-country skis just so they'll have the correct structure for every possible snow condition?
Perhaps some parents will.
But I suspect most of us would rather spend our money on something else as well.
Food, for example.
Or perhaps our own skis. 😀
So Which Structure Should We Choose?
If we're buying versatile sports skis, I consider a relatively fine to medium base structure a sensible choice.
I would be particularly cautious about very deep, coarse patterns if I didn't know exactly which snow conditions they were designed for.
It's not just about the spacing between grooves.
Their depth, shape, orientation and the quality of the finished surface matter as well.
A fine or medium, relatively universal structure allows the skis to be used across a reasonably broad range of conditions.
For specific snow conditions, the underlying structure can sometimes be supplemented with additional manual structuring.
However, not every hand-structuring tool works in the same way.
Some tools mainly produce a temporary impression that can largely be smoothed out by subsequent waxing and heat treatment.
Others actually remove material, making their effect considerably more permanent.
Likewise, there is nothing inherently wrong with machine-produced structures.
On the contrary, a well-produced basic machine structure can be extremely valuable.
So my recommendation isn't to buy skis without any structure. It's to buy skis with a properly produced structure that suits their intended use.
And if we're buying just one pair of sports skis for a child to use throughout the season, the most aggressive structure in the manufacturer's range may not be the best option.
After all, the loudest person in the room isn't necessarily the one who's right.
Fluorine: When a Miracle Solution Becomes a Problem
Historically, various fluorinated materials have appeared in the world of ski bases and glide waxes.
These include fluorinated polymers and PTFE-based additives.
One objective was to influence surface properties and interactions with water.
However, fluorinated chemistry has increasingly raised serious questions about certain persistent substances, their production, use and effects on the environment and human health.
These concerns are also behind current restrictions on fluorinated racing waxes.
It is important, however, to distinguish between different chemical substances and materials.
Not every compound containing fluorine has the same properties or presents identical risks.
Nor can a ban on fluorinated racing waxes automatically be applied to every fluorinated polymer used in ski manufacturing.
Fortunately, for parents choosing children's cross-country skis, the practical conclusion is simple.
Special fluorinated materials are certainly not something we need for ordinary recreational skiing.
We have already explored the history of fluorinated ski waxes, their advantages, problems and gradual restrictions in a separate four-part series.
Molybdenum Disulfide, Graphene and Other Technical Miracles
Another well-known solid lubricant is molybdenum disulfide, commonly abbreviated as MoS₂.
Like graphite, it has a layered structure that can provide low shear resistance under suitable conditions.
It is therefore used in numerous industrial applications where reducing friction and wear is important.
Special additives of this kind may also be of interest in the development of ski base materials.
But their actual benefits depend on the specific formulation and application.
Just because a substance works beautifully as an industrial lubricant doesn't mean it will turn a cross-country ski base into the fastest material in the world.
Snow is a rather unusual partner.
And it often behaves very differently from steel components in industrial machinery.
The situation is similar with graphene and other modern carbon-based materials.
Graphene is known for remarkable mechanical, electrical and thermal properties.
However, its practical effects in a polymer mixture depend on its particular form, concentration and the way it is incorporated into the material.
Antioxidants, stabilisers and other additives may also be present. Their primary purpose is not necessarily to reduce friction directly, but perhaps to improve manufacturing or long-term material performance.
Whatever the additive, one important principle remains.
The impressive name of an additive tells us very little about the overall quality of a ski base.
It's a little like buying a car.
What matters isn't how many exciting technologies appear in the advertising brochure.
What matters is how the whole car actually performs.
And skis aren't very different.
Do Children Really Need Special Ski Bases?
Let's return to the question we asked in Part 1.
How should we choose sensible cross-country skis for children?
And do our little athletes really need different bases for cold, warm, dry, wet and artificial snow?
In most cases, no.
For beginners, correct ski length and stiffness, easy handling, reliable grip and reasonable glide are much more important.
If a child trains and races regularly, differences between ski base materials may become more relevant.
And at a higher competitive level, specialised skis for different snow conditions can certainly make sense.
But even then, I wouldn't begin by asking whether the skis contain enough graphite.
I'd begin by asking whether their construction, stiffness, base material and surface structure suit the intended conditions.
Because a world-class ski base attached to the wrong pair of skis isn't much of a victory.
And a parent who buys four pairs of racing skis for a child who still prefers playing on the little hill behind the house may have just started a very expensive experiment.
What Should We Remember?
A cross-country ski base isn't just an ordinary piece of plastic.
Its properties depend on the polymer, manufacturing process, additives, and the design and finish of the actual sliding surface.
Graphite, carbon particles and other additives can modify the way the material behaves.
The number of longitudinal grooves, the quality of joints and the choice of surface structure can also influence how the ski actually glides.
Colour alone tells us little about ski base quality.
And an exotic additive, complicated geometric design or impressive machine-ground structure certainly doesn't guarantee faster skis.
Choose skis according to their actual characteristics, not the colour of the base, the number of grooves or the number of impressive technical words in the catalogue.
If a salesperson can explain why a particular material or design makes sense, so much the better.
But if all they can say is that it's the latest and greatest technology in the world, I'd be a little more cautious.
After all, the latest technology is sometimes the latest simply because the manufacturer happens to need to sell it right now. 😀
In the final part, we'll examine ski base ageing, surface wear and proper maintenance.
We'll also return to the question of why ski bases sometimes turn grey and why even expensive skis may eventually stop gliding as well as we'd expect.
Because even a very good ski base can sometimes behave surprisingly badly.
And sometimes the manufacturer isn't to blame.
Nor the graphite.
Not even the wax.
Which is rather unfortunate for those of us who enjoy having just one person or thing to blame. 😀