Sintered vs. Extruded bases

[Tele 'til You're Smelly]

Stinkymonday's post in the sand dune thread mentioned that modern K2s have extruded bases. For some reason I thought only bargain skis have extruded bases and sintered bases are better since they holds wax better and are harder- am I thinking about this correctly or are some performance skis still extruded, and if so why other than cost?

[B__]

From:

http://www.tognar.com/waxing_tips_ski_snowboard.html

P-TEX WAX ABSORPTION
For years, most folks in this industry (like us) have told poor unsuspecting blokes (like you) that sintered p-tex has pores or holes in it...and that, when you hot-wax a base, these cavities sorta suck-in and store wax better than regular extruded p-tex bases. Well, we lied...sorry! But we're not totally off-base (pardon the pun), because sintered p-tex does absorb and hold more wax than an extruded base by absorbing it.
Here's what really happens according to Mr. Urs Geissbühler at IMS (a large producer of p-tex) in Switzerland. P-tex is like a super-cooled, fluid-like substance. It's made up mostly of two different types of microscopic regions...tiny little freckles all packed together, if you will. One type is crystalline and the other is amorphous. The crystalline freckles are, as the term implies, hard crystallized regions that don't absorb hardly nothin'. The amorphous freckles are softer, more gel-like, and absorbent. Sintered bases are comprised of about 60% amorphous freckles and 40% crystalline (and a bit less of both of these if graphite particles have been mixed in). Extruded p-tex is just the opposite...60% crystalline and 40% amorphous.
When wax is applied to the base and heated in, it blends into the amorphous freckles... sorta like sugar being mixed into hot coffee. Then, when the base and wax cool again, about half this wax is expelled from the amorphous freckles, like sugar recrystallizing in cold coffee. This is why waxed bases should be allowed to cool thoroughly before scraping and brushing excess wax off.
Incidentally, sintered p-tex is used on about half the skis made today, but on only 10-15% of snowboards (carving boards mostly). Extruded p-tex is used for most snowboards because it costs less, plus has better clarity so base graphics can be seen more clearly.
P-tex is made in different hardnesses, and both are utilized on racing skis. A hard base is usually used in cold conditions because it can better hold up to the greater abrasion of the cold snow crystals. It also absorbs less wax than a softer base, but this is not so important in cold conditions since there usually isn't as much moisture in the snow. Softer bases are preferred for warmer conditions because snow abrasion is usually less, plus the base can absorb more wax...especially important since wax makes p-tex more hydrophobic (waterproof). This reduces the surface tension of water that's usually abundantly present in warmer snow conditions.
Pete Patterson, formerly a downhill racer on the U.S. Ski Team, does wax testing for Swix at the Olympics and World Cup races. To select which skis to use for wax testing, he starts out with about a dozen pair of Salomon skis (usually womens DH models because they're an easier size for Pete to travel with). He waxes them all identically, then skis each pair through the same speed trap. He then selects 5 pair that test at about the same speed (a .1 second variance or so, anyway), and uses these to do Swix's wax testing prior to DH races.

[Tele 'til You're Smelly]

Thanks that was interesting. Still wondering about what most skis, let's say ones designed for backcountry, use- sintered or extruded?

Also- that says soft bases hold more wax, and sintered bases hold more wax- does that mean sintered are actually softer? Or can be either way?

[B__]

It would not surprise me if sintered bases were in general softer than extruded ones. The extruded pattern sections of my Vector BC's seem harder than typical sintered bases, and they don't hold wax for as long. I do believe that the smooth base sections near the tip and tail on Voile's BC lineup are sintered. At least when they are new, you can detect a seam across the base at either end of the patterned section.

I think that most ptex repair material is of the extruded variety, though it can be applied to a sintered base with good results.

[Tele 'til You're Smelly]

I think that most ptex repair material is of the extruded variety, though it can be applied to a sintered base with good results.

my understanding is that it's the same stuff, but extruded is the pellets melted together while sintered is the pellets pressed together under high pressure

[Baaahb]

"like sugar crystallizing in your cold coffee" ??? I wonder how much sugar you need to put in a cup of coffee to have this happen.

[cesare]

There was also the controversy a few years back documented but not actually argued on TGR proposing that the whole idea of waxing is a specious and quixotic quest for speed. In cross country racing, the movement has been simply to scrape and brush the **** out of the base to expose a clean structure. The idea is that the base actually does not absorb wax and that beyond leaving a thin layer that wears off quickly, waxing actually does nothing. The argument said that ptex absorbing wax is a myth because the pores in the base are smaller than the molecules of wax. Brushing is what it's all about.

In my opinion, waxing scraping and brushing are beneficial if for no other reason than they prevent skin glue from sticking to the base compared to a base that is never prepared. When I tune, I use the smallest amount of wax necessary to cover the base, let it cool completely, and then scrape and brush with a brass brush. Any remaining wax is barely visible. I do this every two to four ski days.

[Teleman]

Jeesum I do that once or twice a year.....Teleman

[yersinlepoleAunt]

Another interesting idea is that
it's a total waste of wax and $$ to be
brushing and scraping it off..
Simply iron or rub in an adequate
amount and smooth it with a cork
when it cools..let the snow brush and scrape..
Skiing in spring, and really cold conditions,
clearly show that waxing does (can) do something good,
just never for as long as one would like..

[Tomahawk]

I think scraping and brushing is going to save the adhesive life of your skins. That's why I do it.

[Baaahb]

a good wax job clearly makes my skis glide better and lasts longer than a poor wax job. the difference is much less noticeable on extruded bases; many just use "liquid" glide wax on extruded bases

[LightRanger]

Stinkymonday's post in the sand dune thread mentioned that modern K2s have extruded bases. For some reason I thought only bargain skis have extruded bases and sintered bases are better since they holds wax better and are harder- am I thinking about this correctly or are some performance skis still extruded, and if so why other than cost?

Going back to the original post. Modern K2s do not have extruded bases. None that I've seen at least. I've sold a bunch of them in the last few years. The only extruded skis I've seen are nordic/BC skis, and maybe some cheap park skis. And cheaper snowboards.

Sintered is also harder than extruded, but when you get a hit, it tears out more easily, whereas extruded more easily deforms due to its softness.

[Tele 'til You're Smelly]

Going back to the original post. Modern K2s do not have extruded bases. None that I've seen at least. I've sold a bunch of them in the last few years. The only extruded skis I've seen are nordic/BC skis, and maybe some cheap park skis. And cheaper snowboards.

Sintered is also harder than extruded, but when you get a hit, it tears out more easily, whereas extruded more easily deforms due to its softness.

thanks LR.