What is the main difference between the cheaper and more expensive liquid gliders

Normally the main difference is the life time / stability / wear resistance… in other words how long the improved gliding properties can last under given snow and weather conditions.

 

Normally the cheaper liquids last on the ski base for a much shorter time and therefore provide a much shorter improvement of gliding features.

 

Why? Most of the cheaper liquid gliders are solutions containing two main components: active ingredients dissolved in a carrier. The carrier is responsible for liquid state of the solution, enables application on the ski base in the liquid form. After application the carrier evaporates more or less fast and leaves only the solid component on the ski base.

 

The only way how this solid component sticks to the surface of the ski base is the mechanical retention in the microscopic irregularities and roughness of the ski base surfaces. The chemical bonds are extremely weak.

 

How cheaper liquid gliders can be identified?

 

·      You need to shake the bottle before you properly to mix the active ingredients with the carrier.

·      Often sponge head is used for application.

·      After application you can see a wet film on the ski base.

·      They dry quite fast (5 to 10 min.)

·      You need to brush them softly with nylon brush.

 

Normally the more expensive liquid gliders perform a bit better, but especially last longer, in other words provide the improved gliding features for a longer time.

 

Why? Most of the more expensive liquid gliders contain a component which actively disrupts the surface of the ski base in a gentle way, in other words which allows the active substances in the glider to soak or to be integrated into the ski base. In other words: more expensive gliders create their own irregularities or micro roughness for better integration into the ski base.

 

How more sophisticated liquid gliders can be identified (except for they are more expensive)?

 

·      Normally they are sprays – you spray them or apply with fleece.

·      After application they often create small bobbles on the surface.

·      They need more time to dry / be integrated (normally 25 min. to 30 min.)

·      Often they are not brushed.

Which components of the ski base are the most important

 

 

Even if specialized magazines and articles mention many different additives and ingredients used in ski bases of competition skis, finally we will find out, if we look in much more detail, that there are only two main components which influence the most important features of each ski base type, especially now after fluor ban.

 

First is the UHMWPE itself which defines the features of the matrix. The matrix itself can get touch in contact with snow surface, that’s the reason why PE is used, because currently there is no other polymer with such a low coefficient of friction and so high hydrophobicity available. With respect to other components the matrix is responsible for the wear resistance and fixation of additives.

 

For wear resistance the most important figure is the length of molecular chains, the higher the length of molecular chains, the better the wear resistance. Reaching the value of 10.000.000 the polymer can be hardly processed.

 

Additive fixation in UHMWPE is problematic. The most additives do not form strong chemical bonds with the base matrix. Additives are bound in the matrix either by very weak chemical bonds or by mechanical retention. Especial close to the surface where the contact snow and ski base surface take place especially the mechanical retention decides.

 

The most important additive used in modern ski base types is soot or carbon black. The importance is given by the amount used in the competition ski base types which reaches up to 20 % of weight fraction in Nordic skis and up to 40 % of weight fraction in Alpine skis and by the way how carbon black is fixed in the PE matrix.

 

Some carbon black is incorporated directly in the PE matrix, but most of carbon black is filling the free space or cavities between the PE corns which are sintered together using heat and pressure. Especially the second type of soot fixation is responsible for high values of E-modulus which decides how ski base changes elastically under load.

 

Wax history in the ski base

We know that the very surface of the UHMWPE ski base is created by crystalline, amorphous and transition regions. In crystalline regions no wax can penetrate, transition regions are insignificant with respect to the area, the only ski base fractions where wax can penetrate are amorphous regions.

Amorphous regions consist of disordered structure of PE molecular chains with free cavities which size is in the order of tens of nanometres. In these free cavities there is enough space for wax molecules to get in and get stuck after hot wax application.

If ski base is ironed by temperatures close or above the melting point of UHMWPE which is ca. 140 degrees C the molecular chains of UHMWPE become more flexible and the free spaces between the chains are more easily to be accessed by wax molecules. After the ski base has cooled down again, the molecular chains “freeze” again and wax molecules remain trapped in the nano-cavities.

After skiing wax removers and cleaning brushes are used. Current wax removers evaporate very slowly which means their molecules are larger and heavier than those which were used in the past. They can access the cavities and dissolve the wax, however, they cannot remove the mixture out of the cavities.

Brushes are too coarse to reach the cavities. Some amount of wax - dissolved by removers - will remain in the cavities. After wax removers evaporate, solid wax remains in the cavities. This wax will stay here, until new wax is applied and mixed with the wax history in the ski base.