is the bottom of the board or ski
that is in contact with the snow's surface. It's generally made of a porous, plastic material (often called p-tex), that is saturated with a wax
to create a very quick and smooth, hydrophobic surface.
It is important that the base
be "slippery" with respect to the snow surface and board interaction. Bases
are made to have amorphous areas that are porous to wax.
when maintained, will have a base
structure that not only channels snow, air and water, but leaves it open enough for wax
to penetrate deep inside it. This pattern is created with a stonegrind machine at the factory or a local ski
shop, or with a series of brushes (see the how to wax
article for more info). If a base
is left without wax
for too long, it will begin to oxidize and no longer accept wax
as generously as it once had.
Luckily this is reversible. Through either brushing the base,
or stonegrinding it, you can remove the layers of oxidation from the board and open up its amorphous areas to accept wax
again. If the base
is damaged, it is common to have it repaired in order to protect the core
from exposure as well as reducing friction.
The P-Tex is either cut from a large sheet or squeezed out of a machine much like "Play-Doh". A low maintenance base,
it is the least expensive and the easiest to repair. Extruded bases
are smoother and less porous than other bases. They do not saturate with wax
well and tend to slide slower than other bases. But left unwaxed they do not lose much overall performance. Extruded P-Tex is also cheaper than sintered P-Tex.
material is ground to powder, then reformed with pressure and heat, and lastly cut to shape. A sintered base
is very porous and absorbs wax
well. Sintered bases
slide faster than extruded bases
when waxed, but will be slower if unwaxed for a long period of time. They are more expensive and harder to repair.
may have graphite, gallium, indium or other materials added. These materials are used increase glide, strength, "wax hold" and other desired characteristics.
use a polyethylene material (a kind of thermoplastic) often referred to as "P-Tex", but is more specifically called "Ultra High Molecular Weight Polyethylene" (UHMWPE). The bottom of most modern skis
— the surface that is in contact with the snow — is coated with UHMWPE, treated for compatibility with waxes and with epoxy base
material. These treated materials are known as P-tex, Isospeed, or Durasurf. Because the material is a thermoplastic, gouges can easily be filled.
UHMWPE has extremely long chains with molecular weight numbering in the millions, usually between 2 and 6 million. The longer chain serves to transfer load more effectively to the polymer backbone by strengthening intermolecular interactions. This results in a very tough material, with the highest impact strength of any thermoplastic presently made. It is highly resistant to corrosive chemicals, with the exception of oxidizing acids. It has extremely low moisture absorption, has a very low coefficient of friction, is self-lubricating, and is highly resistant to abrasion (15 times more resistant to abrasion than carbon steel). Its coefficient of friction is significantly lower than that of nylon and acetal, and is comparable to that of Teflon, but UHMWPE has better abrasion resistance than Teflon. It is odorless, tasteless, and nontoxic.