There are at least four interconnected factors that need to be balanced when developing a skin adhesive.
Temperature range for Adhesion.
This is the range within which the adhesive will remain bonded to a give surface. At the lower end of the range, the adhesive is generally too “hard” or frozen, and simply has no tackiness. In temps colder than the low end of this range the skin will simply fall off the ski, regardless of the temperature at which it was applied. The upper end of the range is not of much concern for making climbing skins because typically thecohesive strength decreases to the point that the adhesive will leave significant residue on the skis. Necessary range for climbing skins: -30°F to +70°F Climbing Skins Direct Adhesion Temperature range: -40°F to warmer that you should get your skins!
Temperature range for Application.
This is the range within which the adhesive can be applied to a surface and be expected to have “tack” and to stick to a surface. This is commonly confused with the Adhesion Temperature Range. Outside the low end of the Application Temperature Range, skins cannot be applied to the skis. However, skins will stayattached to your skis in much colder temperatures than they can be applied. This is why it is recommended that skins be kept warm (in your coat pocket for instance) before applying to skis. The upper end of this range is not usually applicable for skins because typically the cohesive strength decreases to the point that the adhesive will leave significant residue on the skis. Necessary range for climbing skins: +5°F to +70°F Climbing Skins Direct Application Temperature Range: +5°F to warmer that you should get your skins!
The cohesive strength of a material is a measurement of how well the material bonds with itself. This is the factor that controls how resistant the adhesive is to leaving residue on the ski. If the cohesive strength is too low, the adhesive will stick to other surfaces better than to itself. Thus as the skin is peeled off the ski, globs of glue are likely to separate from the skin and remain on the ski base. If the cohesive strength is too high, the adhesive would rather remain stuck to itself than to any other substance, and consequently the adhesive won’t stick to any other surfaces. With skin adhesive, typically the cohesive strength increases as temperature decreases…which is why skins that were stuck together indoors and then peeled apart when cold are nearly impossible to separate! Conversely, as the temperature rises, the cohesive strength decreases and the adhesive is more likely to separate from itself and leave reside on your bases.
The peel strength is the measurement of the actual mechanical strength of the adhesive’s bond. Thus the peel strength of two skins stuck together is a actually a measure of the cohesive strength. For skins, if the peel strength is too high, the skins are difficult to remove from your skis, (or anything else they touch!), but if the peel strength is too low, the skins won’t remain stuck to much.
These factors are generally not compatible and optimization requires many compromises. It is a matter of getting the desirable range of each parameter to overlap with the desirable range of all the other parameters. For instance while our adhesive does not have the lowest Application Temperature on the market, (we are still lower than the adhesive used on the Ascension™ skins), our adhesive works much better in warm temperatures, and will not leave residue on ski bases or edges. Our cold temperature adhesion is effective to –40°F, while our effective application temperature is +5°F. In addition we have found an adhesive with a lower cohesive strength so our skins are much easier to peel apart and still have great performance in cold temps. In all, we feel we have the best balance of characteristics currently available. There are conditions when other brands will out-perform our adhesive, but there are many more conditions where our adhesive will outperform the competition!
An interesting side note is that the adhesion temperatures of most North American skins are very close, while most European skins don’t adhere or apply in cold temperatures.