Technical snow and its specific features

 Technical snow. We have already touched on this topic several times. We have already mentioned several times that technical or artificial snow, in short, so-called man-made snow, is not actually real snow. Today we will take a closer look at the specifics and unique properties of this human creation.

 

Artificial snow is produced by using a pressure pump to drive a stream of water to a sprayer, where it is broken into small water droplets of approximately 0.1 mm in size. The droplets of the broken water must not be much larger or much smaller than 0.1 mm. Larger droplets risk not freezing sufficiently, while smaller droplets risk evaporating after contact with cold air or being blown away by the wind outside the snow-covered area.

 

As soon as a droplet of sprayed water hits cold air, the temperature of which should not be higher than about -2.5 degrees C when using chemically untreated water, a kind of ice shell or ice coating first forms on the surface of the water droplet, which seals the rest of the liquid water inside. As soon as this ice shell starts to fall towards the ground, the liquid enclosed inside has approximately 1 second to freeze due to the cold air.

 

If this does not happen, it is necessary to let the artificial snow "ripen" or "freeze out" in piles on the ground, where the freezing out already occurs much more slowly and due to the insulating properties of the snow and the increasing temperatures towards the ground, part of the internal water can remain in a liquid, i.e. unfrozen, state.

 

It is this possible proportion of liquid water inside the ice grains that causes artificial snow to often be wetter or more humid than natural snow under comparable conditions.

 

The relatively small size of the so-called seed droplets of technical snow (the optimal size is about 0.1 mm) is the reason for the second characteristic property of technical snow, which is its high density and bulk density. Small droplets of dispersed water form small ice grains with an average size of 0.1 to 0.8 mm, which are also very round or rounded. These small round grains fit tightly together and leave almost no space for air between them, which greatly complicates the process of snow freezing after it hits the ground, where the access of cold ambient air ensures the complete freezing of the ice grain.

 

The last important characteristic of artificial snow is the round or spherical shape of the small grains. This third – characteristic – characteristic of artificial snow, which so significantly distinguishes it from natural snow, is caused by the opposite direction of freezing of artificial and natural snow. While natural snow grows from the core towards the surface (air moisture condenses on the germ of dirt or dust somewhere high in the clouds), artificial snow freezes from the surface to the core (when a water droplet comes into contact with cold air, a kind of ice shell is first formed, which encloses the remaining still liquid water, which then – during a short flight towards the ground – must freeze to the center or core of the grain, if this does not happen, there is a real risk that the center of the ice crystal will remain filled with liquid water).

 

Repetition is the mother of wisdom. Let us therefore repeat the basic characteristic properties of artificial snow. Artificial snow is made up of small ice grains with an average size of 0.1 to 0.8 mm. Ice grains are primarily round or rounded, without sharp edges or facets. Technical snow therefore has a high density and bulk density (shortly after production it reaches a weight of about 500 kg/m3). If technical snow is produced at higher temperatures or the broken droplets have a very short flight path in cold air before hitting the ground, it tends to be significantly wetter or moister than natural snow under similar conditions, which is caused by the liquid or unfrozen center of the ice crystals.

 

The above specification suggests that man-made snow should cause a relatively low level of abrasion or mechanical stress on the ski base. The grains are round, moist, small, without sharp edges and facets, higher humidity blocks electrostatic charge... But in fact, the opposite is true. Anyone who has even the slightest experience with servicing skis, especially cross-country skis, knows that artificial snow is enormously aggressive and abrasive and causes enormously rapid wear or even "abrasions" of even the most tenacious waxes. In other words: technical snow is much more abrasive than practically any natural snow, including aggressive and abrasive firns or angular-grained snows deep below freezing point...

 

But how can we explain this? Where does this high level of abrasion and aggressiveness come from, when technical snow should be anything other than aggressive and abrasive due to its shape, humidity and details.

 

The explanation is very simple and at the same time deeply hidden. As we mentioned above, technical snow freezes from the surface to the center. A kind of shell or ice shell first forms on the surface of the water droplet, inside which the remaining part of the liquid water remains closed. This liquid water then freezes from the surface to the center. We all know what happens if we forget a bottle of beer or wine in the freezer, which we put there for the purpose of rapid cooling and which we eventually forgot about. Yes, that's right. The beer or wine tears the packaging, usually a glass bottle. Why, liquids increase their volume when changing from liquid to solid. The force that acts on a glass beer bottle is so great that the bottle eventually breaks.

 

However, when the ice droplets of artificial snow gradually freeze, the shell or ice cover does not burst, and all the energy of the gradual increase in volume, which must fit into the same space, is reflected in the "densification" or "compaction" of the locked water in the ice grain. Yes, the molecular lattice of the frozen water changes, which is then much stronger, denser and much less subject to temperature fluctuations and melting processes.

 

Yes, that's right, the ice grains of artificial snow are ice grains of compacted water, which are enormously strong, enormously hard, enormously stable, and therefore enormously aggressive and abrasive in relation to other materials, such as ski bases. The ice grains of compacted water are also much less subject to temperature influences and melting processes, which is why technical snow can withstand even relatively high temperatures above freezing, where natural snow would have melted completely long ago.

 

As we know, a significant part of the World Cup competitions in all possible skiing disciplines are already taking place mainly or primarily on artificial or technical snow. With regard to the progressing climate changes and the retreat of the natural snow line to ever higher positions, it can be assumed that skiing on technical snow, and not only on the summit, will become an increasingly frequent and common phenomenon.

 

However, skiing on artificial snow places significantly higher demands on the chemical, but especially mechanical properties of the ski base than skiing on natural snow. In terms of the chemical properties of the base, this is mainly hydrophobicity and dirt-repellency (as we have repeatedly mentioned above, technical snow is much wetter and at the same time much dirtier), in terms of mechanical properties, this is mainly hardness, toughness and abrasion resistance (as we know, technical snow is very aggressive and abrasive and its hardness often exceeds the own hardness of the base, which is manifested by the so-called effect of plowing the base with ice crystals).

 

It is a big question whether standard hydrocarbon waxes, even supplemented with various additives, are and will be able to meet these increasing demands for hydrophobicity, dirt-repellency, but above all hardness, toughness and abrasion resistance. Perhaps the time and space have come to completely abandon wax technology, or at least supplement it with new, more promising and effective alternatives...

How does the wax stick to the ski base? - Part. III.

We know that there are main principles how waxes are connected to the ski base. Some waxes penetrate into the inside molecular structure of the ski base which is accessible for waxes only if wax is in the liquid state and ski base is more flexible due to heat. Some waxes stay on the surface and “fill” only surface imperfections and roughness where waxes are partly retained in the “open” surface structure mechanically partly connected with weak chemical bonds.

Attention: surface imperfections and roughness cannot be confused with grinded or imprinted additional structure created by stone-grinding machines or manual structuring equipment. Surface imperfections are related to flat ski base here.

If wax molecules in liquid state enter once the inside molecular structure, fill the “closed” cavities inside the molecular structure of the ski base and change back from liquid to solid state, they cannot be removed again by either chemical agents or mechanical cleaning.

What does it mean?

This means that skis which have been waxed cannot be set back to “zero” status any more even if they have been used and cleaned chemically and mechanically.

What does it mean?

This means that any wax application is reacting / is mixed / is influenced by the wax molecules which remained “locked” inside the “closed” cavities inside the molecular structure of the ski base and which become liquid again as new wax layer is ironed.

What does it mean?

This means that after the very top layer of liquids / speeders / accelerators is worn off - which normally happens within a few hundred meters or a maximum of a few kilometers (depending on the snow type), your ski will glide on a mixture of old and newly applied waxes.

Even if you see a grey or white base surface, the cavities inside the molecular structure of the ski base are filled with old wax molecules which are locked in the closed cavities.

 

How does the wax stick to the ski base? - part II.

To understand the way how the additionally applied wax sticks to the ski base, we need to go a bit deeper into the topic…

Here we do not distinguish between chemical bonds and mechanical retention in general as we did in the part I., but we concentrate on the position of the wax in or on the ski base.

If we speak about how wax sticks to sintered UHMWPE ski base types, we need to distinguish between 1. wax penetration into the inside structure in the ski base and 2. wax adhesion to the ski base surface.

1.    wax penetration into the inside structure in the ski base

If you take a piece of a new ski base strip coming directly out of production, weight it and wax it as a usual ski base (apply wax, iron, let cool down, scrap and brush excess wax) and weight it again, you will find out, the piece of ski base strip increased in weight. The weight increase will depend on the type of ski base and the amount of additives incorporated, but it will normally range between 0,6 to 3,0 mg/cm2

This wax penetrated into the ski base does not take part directly in gliding features of the ski base, it improves the gliding features indirectly only: a. it helps the wax layers on the surface to be fixed on the ski base, 2. it can restore worn wax layers on the surface under special conditions, 3. it improves general conditions of the ski base.

2.    wax adhesion to the ski base surface

On the very surface of the ski base the wax layers retain partly mechanically in fine microscopic imperfections which are filled with wax, partly with help of chemical bonds. This very top surface is the main snow – ski base interface until it wears. To increase the life time of the very top layers, ski base surface is structured which means: 1. it total surface is increased significantly, 2. surface receives a height profiles with different shapes. Especially the height profile and increased total surface promote the wax layer life time on the very top surface.

Conclusion

Wax penetration helps 1. to fix the top layers in the ski base / snow interface which decides about gliding features, 2. to prolong some gliding features after the top layer has worn off.

Wax adhesion to the very top base surface is responsible for 1. the real interface between ski base / snow interface which decides about gliding features, 2. enables a short life time of top layers only.

 

What is the main disadvantage of racing or competition ski base types?

 What is the main disadvantage of racing or competition ski base types?

 

For race skis the best ski base types are use. Normally three types are offered at least: race ski base for cold, wet and universal conditions. The individual types differ in many parameters (see our previous articles).

 

For rase ski base type a wide range of additives and special substances is used to optimize the gliding features under given conditions. These additives and additional substances also do differ depending on the ski type (different additives are used for cold and wet conditions of course).

 

Almost all race ski base types have one common thing: the UHMWPE matrix is filled with additives and additional substances to maximal possible extent for maximal possible performance!

 

This absolute advantage of race ski base types on the one side is the main disadvantage of race ski base types on the other side.

 

Rase ski base types are filled with additives up to the edge / to maximal possible extent for maximal possible performance. What does it mean?

 

Almost all possible free space inside the molecular structure of the ski base is already “occupied” by all possible additives. What does it mean?

 

All wax-based products (base waxes, powders, liquids, speeders etc.) rely especially on the mechanical retention in the ski base, especially in amorphous regions of the ski base. Chemical bonds of wax-based products are normally too weak.

 

Mechanical retention is so strong as many cavities inside the molecular structure can be filled with waxes. In race ski base types almost all free cavities inside the molecular structure are already filled with additives which were added in the ski base production process! What does it mean?

 

There is almost no space inside the molecular structure of race ski base types to absorb any waxes or gliding agents additionally applied. You can put them only on the surface. What does it mean?

 

You are losing the mechanical retention and your additionally applied products need to rely expecially on chemical bonds which are normally very weak!

 

What is no-wax chemistry?

 What is no-wax chemistry?

 

The most of no-fluor wax systems (base waxes, powders, liquids, speeders etc.) are still based on waxes (different types, blends of waxes enriched with different additives).

 

All wax-based products rely especially on the mechanical retention in the ski base, especially in amorphous regions of the ski base. Chemical bonds of wax-based products are normally too weak.

 

Mechanical retention in the ski base has its limits which cannot be overcome.

 

That’s the reason why several ski wax manufacturers approached the no-wax way.

 

How it works?

 

No-wax chemistry products contain normally 3 different components. First component is an etching agent which is used to etch / change the surface of the ski base slightly in order to prepare it for absorbing gliding agents. Second component is a binder / carrier which is normally a polymer with low-melting temperature which is filled with the respective gliding agents. Binders are needed because the gliding agents normally do not stick to UHMWPE even if etched slightly. Third component are gliding agents themselves which are very often nano-particles of different substances.

 

After application the ski base surface is etched slightly, the binder filled with gliding agents is entering the slightly disordered ski base surface and unneeded substances evaporate as a result of which the no-wax product will change the status from liquid to solid. Finished. Ski base is coated with a polymer-like agent continuously.

 

 

How to use REX NF 41 liquid glider - comments...

Rex recommends to use the NF41 liquid glider as special glider for men-made snow. As we know, men-made snow is very abrasive in wet and extremely abrasive in cold conditions.

In other words: the main parameters which decide about the quality of the product and gliding features on men-made snow are hardness and wear resistance combined with hydrophobic and dirt-repelling features.

I was quite surprising for me that REX NF 41 works a liquid glider and is applied cold.

Below some comments and ideas related to the product and application method.

NF41 seems to be a very interesting product... it obviously does not rely on mechanical retention inside the micro-structure of the ski base only. Why? First it is applied cold only which means, the nano-structure inside the ski base cannot be reached for mechanical retention, mechanical retention inside the micro-structure cannot be sufficent for men-made snow which is extremely abrasive. Second the preparation steps before application do not include brushing with fine steel brushes to open the ski base, remove old wax residues and refresh the micro-structure... Conclusion: NF41 needs to be fixed chemically directly to UHMWPE. To achieve reliable chemical bonds the product needs to develop stronger bonds than the normal van der Walschen bonds which are too weak or modify the UHMWPE surface slightly to get inside the polymer without ironing! Both apporaches are very interessting, especially if combined 

What seems to be a bit strange is the use of nylon brush for preparation. It could be explained by the fear of the developers of NF41 that the use of a fine steel brush could contaminate the surface with old wax residues which could impact the chemical reactions on the surface negatively. The presence of hard and very hard nano-components in the product is showing the deep understanding of NF41 developers for what really matters when gliding on hard abrasive snow like men made snow below zero. To fix the hard layer on the surface instead inside the surface of the ski base could be also very befefitial... I personally do not like any movements against the gliding direction during the application process and need to check the function and composition of GOLD LIQUID product, but after long time a very interesting product with a very reasonable application method. If it works, it would be a great development step!

How to use SKI GO CM 26 - comments...

SKI GO recommends to use this product for wet warm conditions. Wet and warm conditions are specified by water film in the interface between ski base and snow surface which can be differently thin or thick depending on the amount of so-called free water in the snow. Free water is water inside snow surface which originates from ice crystals or ice grains melting. The higher the free water content inside snow surface, the thicker the water film between snow surface and ski base surface.

 

ISSUES

 

GRAPHIT WAX as base

 

SKI GO recommends to use GRAPHIT WAX as first layer under the product CM 26, they explain the application of black wax containing either graphite or carbon black as separation or stabilisation layer which should block substances below the competition wax to interfere with it. To be honest this is very strange idea. Why? A Black wax containing either graphite or carbon black reacts the same way with the ski base as any other hydrocarbon wax with additives. It penetrates amorphous regions and cannot penetrate the crystalline regions of the ski base. In amorphous regions hot-applied HC wax with additives is retained mechanically in cavities inside the UHMWPE. Graphite works as dry lubricant, carbon black as spherical nano-particles increases hardness, improves electro- and heat-conductivity, improves abrasion resistance. As you can see no features which are relevant in wet and warm conditions. Black wax containing either graphite or carbon black will fill the cavities inside the molecular structure of UHMWPE. Especially the spherical nano-particles of carbon black will reduce the ability of the following layers to connect to UHMWPE.

 

The idea of a stabilisation of separation layer is pure nonsense!

YELLOW HC WAX as another base 

 

SKI GO recommends to use YELLOW HC WAX below the CM 26 product. Special recommendation is not to brush the ski base after application of this layer. To be honest this is another very strange idea. Why? With brushes excess wax out of structures is removed, at least partly. If ski base is not brushed after wax hot-application, the structure grooves will remain filled with wax, this amount of wax is huge compared to amount wax which would be on the ski base if brushed.

 

If you apply the CM 26 product on such a surface, you will dilute the applied product significantly. You will create a mixture of YELLOW HC WAX (partly mixed with the black wax) and CM 26 product. If the product CM 26 should have very specific features regarding water and dirt repellency, you would reduce them due to mixing it with another product.

To dilute a specific product with promised excellent water and dirt repellency does not make sense!

 

DIRT REPELLENCY

 

Warm and wet conditions contain normally a high amount of free water but quite often also a high amount of dirt which also needs to be repelled. In wax-based products normally short-chained wax types are normally used due to their optimal water repellency features and low friction values. Short-chained wax types have, however, also some disadvantages: they are not abrasion resistance (no big issue under wet conditions) and not optimal dirt repelling.

Dirt repelency should be tested in detail!

 

What is crucial to achieve a reliable kick? Part IV.: correctly choosen kick waxes

Kick ski waxes are not easily to be used, for this reason they are often replaced by different alternatives as e.g. mohair skis, wax tapes, no wax skis with nano-structure etc.

We recommend to use kick waxes if snow conditions are stable and predictable, for example when they do not change for longer time (e.g. several days).

Under stable and predictable snow and weather conditions kick ski waxes can be used safely and reliably without any big issues.

If you are not experienced enough DO NOT USE kick ski waxes in case of snow fall, close to zero degrees, any time when snow or weather conditions change fast.

General advice how to use kick waxes:

• apply kick waxes in kick zone only
• NEVER combine kick waxes with alternatives
• always start with a colder / harder wax applied in a thin layer
• hard kick waxes need to be rubbed by a cork
• before you “go” to a warmer / softer wax, try to apply more thin layers of a colder / harder wax
• do not apply more than ca. 4 thin layers
• hard waxes are dedicated for crystalline snow conditons or snow conditions where the snow crystalls did not lose their forms and shapes completely
• clisters are dedicated for transformed snow conditions or snow conditions where original snow crystalls have transformed to more or less oval cornes of different size
• you can put clisters on hard waxes but not vice versa

Why different structures need to be developed for ISANTIN?

In fact structures created with stone-grinding machines or manual rillers do not normally touch the snow surface. After the ski base is structured, it is normally cleaned chemically (to remove the cooling and greasing agent residues) and mechanically (to remove the grinding solid residues and unwanted hair) and hot waxed (to create protection film and modify ski base surface for respective snow and weather conditions).

Hot-wax-approach consists of several steps:

 1. wax is applied on the clean ski base surface (melted wax can be applied with wax applicator, solid wax can be rubbed on the ski base, wax can be melted on the iron and dropped as liquid on the ski base etc.), 

2. wax is ironed with recommended ironing temperature for recommended ironing time (normally from tip to tail with the target to make the wax penetrate to cavities inside amorphous ski base regions where wax molecules can be retained mechanically after ski base and wax cooled down to solid state), 

3. ski base with ironed wax layer is allowed to cool down for ca. 20 minutes at mediate temperature, 

4. excess wax is removed with scrapers first, from tip to tail, with sharp plastic scrapers carry-fully in flat ski base areas, 

5. after excess wax was removed from flat ski base areas, excess wax is removed out of water drainage gutter or gutters with oval plastic scrapers,

6. removing wax out of flat ski base areas with help of scrapers pushed more wax into grooves of structures which are now completely filled with excess wax which was compacted by scrapping,

7. grooves of the structure created with stone-grinding machines or manual rillers need to be restored, i.e. excess wax need to be removed out of the grooves, to remove excess wax out of the grooves brushes are used, normally fine steel or bronze brushes are used to remove excess wax out of the grooves,

8. fine steel or bronze ski brushes have normally hair 25 mm long, with bristles 0,1 mm thin which is bundled to bristle bundles with diameter of ca. 6 mm

9. if the grooves are 0,5 mm wide and ca. 0,05 mm deep (which is a middle fine structure pattern) it is quite obvious, that bristles 0,1 mm thin cannot reach the very bottom of the grooves, or in other words: remove all the excess wax out of the grooves,

10. it can be estimated that the lower 1/3 of the grooves remain filled with wax which is again compacted by the brush bristles

11. wax application makes the originally manufactured structures shallower and more rounded.

Unlike the hot-wax-approach ISANTIN covers the ski base surface with a very thin layer which is ca. 1 to 2 microns thin and thus copying the structure relief almost perfectly, in other words: after ISANTIN application the originally manufactured structure with help of stone-grinding machines or manual rillers remain more or less the same, only covered with an ultra-thin ISANTIN layer.

 

In fact the good performance of structures is tested and approved for waxed skis, not for plane = unwaxed skis which means the shallower and more rounded structure shapes after wax application are a part of the structure success.

 

If ISANTIN does not change the structures similarly to waxes, it is needed to change the structures in fabrication process = make them shallower and more rounded in stone-grinding process for ISANTIN.

What is the main difference between cold and wet ski base?

Competition skis or racing skis are normally offered with three different types of ski base: cold ski base for cold, hard and abrasive snow conditions, wet ski base for wet, soft snow conditions with water film in the interface and universal ski base for transmission snow conditions between cold and wet.

Ski base compositions differ in the used additives to comply with different snow conditions.

Soot or carbon black in cold ski base types is used to increase hardness, wear-resistance.

Graphite in lamella form in cold ski base types is used to improve gliding features and electric / heat conductivity.

Metal oxides in cold ski base types are used to increase hardness and wear-resistance.

Molybdenum disulfide in wet ski base types is used to improve water and dirt repellency.

Wax like additives in wet ski base types are used to improve gliding features.

Are the different additives used in cold and wet skis the main difference between cold and wet ski base types?

I would say NO, they aren’t...

I would say that the main difference between cold and wet ski base types is the different ratio of crystalline and amorphous regions or fractions and the different wax intake capacity of those fractions.

UHMWPE which is the main material used for production of racing ski base types is a semi-crystalline polymer which consists of crystalline - for waxes and most types of additives inaccessible - regions and amorphous regions where the most additives are allocated and where the additionally applied wax is connected with the ski base. Crystalline and amorphous regions are normally separated by transitional regions which are - compared to micron-sized crystalline and amorphous regions - in nano-meter scale.

Cold ski base types have the majority of crystalline regions which are harder, compacter and more wear-resistant, but cannot absorb any additives and waxes (thus they are more or less pure UHMWPE), wet ski base types have a higher fraction of amorphous regions which are softer, modified by additives, contain cavities to absorb waxes...

 

This is the main difference between cold and wet racings skis :-) 

 

How does the wax stick to the ski base? - part I.

It is common knowledge that ski bases are waxed. Many wax manufacturers offer liquid waxes where the wax is dissolved in a rapidly evaporating agent. With a sponge you just apply liquid solution of wax and solvent on the ski base and after the solvent evaporation your ski is ready to be used with improved gliding features!

Is it really true?

To answer this question, we need to understand how the wax sticks to the ski base. Does it stick by chemical bonds or by mechanical retention?

The way how waxes stick to the ski base depends especially on the type and features of the ski base. Cheaper extruded ski base types do not have NANO fibril structure to retain waxes mechanically, thus they need to stick to the ski base by chemical bonds only.

 

Chemical bonds are – however – very weak, thus the abrasion resistance of such a wax layer is very low. In other words: a wax layer – especially liquid wax layer – applied on the cheaper extruded ski base will wear off in several hundred meters or max. kilometers depending on snow conditions.

 

More expensive sintered ski base types have NANO fibril structure on the very top surface to retain waxes mechanically, thus waxes are mixed with the base material to a new layer consisting of both wax and ski base material.

 

Mechanically retained wax molecules are protected against abrasion forces, thus their life time is relatively good. Mechanical retention is – however – supported by heat, thus hot wax application is recommended here. Cold liquid wax application will hardy penetrate deep enough.

Conclusions

Waxes stick to cheap extruded ski base types by weak chemical bonds only with very low life time of wax coating. Waxes stick to more expensive sintered ski base types by mechanical retention with good life time. Liquid wax application seems to be waste of money in both cases.

How deep can waxes penetrate into the ski base?

Waxes penetrate into the ski-base, however, the penetration depth is very small, according to many different research studies the penetration depth is max. 1 microns, 1.000 nano-meters.

Regardless of research study results the value of max. 1 microns, 1.000 nano-meters for wax penetration into the ski base material seems to be very realistic.

• the top surface of the ski base is created by NANO fibre-like structure where wax molecules are accommodated in free cavities, the normal length of the NANO fibres or depth of the NANO fibre-like structure is ca. 250 nano-meters
• in this “open” top surface there is enough free space to accommodate wax molecules
• inside the NANO fibre-like structure which depth is ca. 250 nano-meters are cavities and free spaces in the size of a few tens of nano-meters whereas the size of individual wax molecules is amounting to a few of nano-meters
• in this “open” top surface the most of wax molecules are accommodated
• some wax molecules can also penetrate a bit deeper into the ski base but only in so called amorphous regions inside the bulk polymer, crystalline regions cannot be entered by wax molecules
• below the open top fibre-like structure, i.e. in the bulk polymer the free cavities are - however - much smaller (typical range for UHMWPE is 5 to 20 nano-meters)
• at the same time the very top surface of the ski base consists of crystalline regions and amorphous regions separated by transitional regions, waxes and additives contained in waxes can be absorbed in amorphous regions only, crystalline regions are not accessible for waxes and additives.

Most of wax molecules are accommodated in the open top surface which is not much deeper than 250 nano-meters. Wax molecules can be retained between the NANO hairs. Wax molecules and NANO hairs of the polymer create the so called gliding surface.

 

What are the main weaknesses of waxes? Part no. II – wax softness

Waxes are normally soft, much softer than the material of the ski base. Even if ski wax manufacturers try to mix hard waxes for abrasive and aggressive snow conditions, waxes are normally softer than the ski base itself.

 

If softer waxes are mixed with the ski base material in the top surface of the ski base creating the mixture called gliding surface, the result is always softer surface of the ski base or softening of the ski base surface by adding the wax.

 

The hardest waxes offered currently on the ski wax market like Toko X-Cold Powder / Blue X-Cold, Holmenkol Ultra Base Cold, Swix CHX4 / HSX4 / PS4 (cold powder blue/green series), Maplus Race Base Cold – reach the hardness 40 to 50 shore D which is still below the hardness of the ski base which is normally 65 shore D.

 

If we consider that the wax absorbing capacity in cavities inside molecular structure of a ski base is ca. 5 to 30 % of the thin top layer of the ski base, we can say that on the surface amounting to max. 255 cm2 and min. 38 cm2 of the total 765 cm2 the hardness is reduced by ca. 23 to 38 per cent.

 

If we consider that especially the hardness is the most important factor influencing the gliding qualities or friction especially in cold, hard and abrasive snow conditions, then it could mean that wax application under these conditions is contra-effective.

 

Fortunately for ski wax manufacturers, the question is not as straightforward as it might seem at first glance. It is true that the application of soft waxes reduces the entire hardness at least in the extent where wax molecules are accommodated inside the ski base material. On the other side ski base is protected and intermolecular bonds between ski base surface and snow surface can be blocked thanks to wax application.

 

We need to apply waxes also under cold, hard and abrasive snow conditions to protect the ski base and block intermolecular bonds. At the same time wax application will always decrease the ski base hardness. Especially the hardness is the most important factor influencing the gliding in cold and hard snow conditions.

What are the main weaknesses of waxes? Part no. I - wax bonding to ski base

Ski waxes are for sure the most popular and most common agents to optimize gliding features for particular snow and weather conditions.

For each snow condition and for any temperature range there will be many different waxing options to be used.

What are - however - the main weaknesses of waxes especially in competition ski service?

The main weakness of ski waxes is the way how they connect with ski base.

Even if this statement sounds very theoretically, the consequences are practical and enormous.

Ski base consists of PE molecular chains enriched with different additives in NANO level. PE molecular chains create on the ski base surface a fiber-like structure with many small cavities and free spaces. If we consider that the normal length of NANO-fibers on the ski base surface is amounting to ca. 150 to 350 nanometers, the size of cavities can be estimated in the range of a few tens of nanometers. This is enough free space to accommodate wax molecules, especially if they are highly-mobile due to liquid state by ironing.

Fiber-like structure on the ski base surface and wax molecules accommodated in the free cavities inside the fiber-like structure create a new gliding surface on the top of the ski base which is a mixture of the fiber-like structure and wax molecules.

Already this new gliding surface is more a mosaic consisting of different PE-stones, wax-stones and additive-stones. Imagine what will happen if a second / third / forth etc. wax layer is ironed on the mosaic-like gliding surface... The diversity and variability of the gliding mosaic will be increased dramatically.

After wax application - especially if more wax layers are applied - a unique and original surface is created on the top of ski base. This gliding mosaic-like surface is so unique that it cannot be repeated twice. Most probably on each ski of one ski pair a different mosaic-like gliding surface is created. This is very probably the reason why competition ski service is more magic and spells than science! Results can be hardly repeated!

What is crucial to achieve a reliable kick? Part III.: correctly defined kick area of the ski

In the article "What is crucial to achieve a reliable kick? Part I.: right stiffness and length of the skis” it was explained that skis base for classic cross-country skiing style consists of three parts / areas, two gliding areas (one in tip and one in tail of the ski) and one kicking area (in the centre of the ski).

If the skier is standing on both skis, in other words skier’s load is transferred to both skis equally, the middle area (kicking area) should not touch the snow surface and the skis should glide on the snow surface in the tip and tail areas (gliding areas).

In the opposite if the skier concetrates his/her load on one of both skis, the middle area is pressed down and get in touch with snow surface enabling the kick.

For a reliable kick is thus responsible stiffness and length of the skis (they must correspond with the weight and height of the skier) but also the length and position of the kicking area.

If the kicking area - where kick waxes are applied - is A. wrongly positioned along the ski or B. too short or too long no reliable kick can be provided.

If the kicking zone is correctly positioned, but too short the consequence is missing kick but still good gliding properties.

If the kicking zone is correctly positioned, but too long the cosequence is A. a reliable kick but bad gliding properties or B. freezing wax with no kick and horrible gliding properties or C. skis do not enable any movement.

If the kicking zone is incorectly positioned, the result is normaly too long kicking zone with consequences A / B / C depending on other factors as snow conditions, wax type etc.

Conclusions

Define the kicking area where kick waxes are applied carefully before you start to ski. If you do not know the kicking area, apply the kick waxes in a short window which can be increased with insufficient kick. In direction to ski tail the kicking zone ends latest where the ski boots end. If you need to improve kick properties by enlarging the kicking zone, go direction to tail first and stop at ski boot end. After you have reached the ski boots end, enlarge the kicking zone in direction to tip.