Food for thought.
Food for thought.
I think it depends on how bad they are but at the least, they typically won't hold wax as well as the sections that don't have those dry spots.
Base grind, or a metal scraper, or something like SkiVisions base tool. @Jacques has a lot of tuning videos up, including at least one on renewing a base that has been overheated or otherwise abused.
If you've got any urge to do the work yourself, I'd invest in the equipment and make sure it's done right. It's really remarkable how much wax a newly-scraped base will absorb.
UHMW PE doesn't "dry" out, and is very chemically inert. The "dry" areas are abrasion. Spend a lot of time training on ice in a race course, and you will get abrasion fuzz no matter how much you wax. The only way to remove it is to scrape it off and get back to smooth plastic. If the entire base is abraded, the easiest thing to do is get a quality stone grind from someone who knows what they are doing.
I have found that the newest race grinders that impart a very fine structure and leave a strip of base blank (smooth, no structure) along the edges really help preventing abrasion on the base if you ski/train on hard ice.
On junk and rock skis I just use Jacques method of using a very sharp metal scraper to clean the base up as much as possible, then put some linear structure in with a coarse stone, wax and scrape. No need to put a $130 race tune on something I am going to trash early or late season.
Will that's just because your mind doesn't work the same way as Sam's does. ;)
I will say your explanation is clearer to me. But that's just me... and I guess you.
Good info from both of you.
There are two kinds of what polymer physicists call "Free Volume" in a ski base.
The first is in the space between polymer chains in an individual polymer granule.
Wax gets here through a solution diffusion process and that takes heat and time
The second is porosity between the particles of the compacted sintered base material.
Extruded bases don't have this volume and don't hold as much wax as sintered ones.
I used to buy into the drying out of the bases too, but I'd still get those white sections on skis that I knew had been waxed tons of times, including the morning of the day that the white showed up.
I now have learned that using my brass brush before waxing gets rid of the white, so my belief is that it's actually wax that has come up to the surface.
It's not really "wax that has come up to surface" but it's really dry base, or abrasion or however you want to call it. Thing is, wax doesn't last long, and on the end of normal day, you end up with no wax on skis (sometimes a bit sooner, sometimes a bit later, depending on snow, humidity, temperature, speed etc.). So even skis, which are waxed regularly (after every skiing) are "dry" by the end of the day. Thing is, with waxing them after this and before next skiing, you get wax back into ptex and all is ok, with leaving them, those "pockets" are filled with dirt and when you repeat this for several times, you have skis which are basically to throw away by the end of season, as sometimes things get that bad, that no stone grinding helps "renewing" that ptex.
I am familiar with sintered materials and what you are saying is spot on. Add the abrasion issue (or theory) to your information and I think that covers what is going on with your ptex and wax. If there was no porosity in the base, then brushing wouldn't be necessary. I even think that there is "manmade" porosity, aka Structure, that also increases the wax holding capacity. DTOM also explained to me in another post that "glide waxes" stick best to base prep waxes, so saturating the base with base prep wax and then adding a layer of glide wax lasts longer than just adding glide wax constantly.
Along the same lines, I've noticed that using only mid temp or cold temp wax will also dry out the base over time, gradually, even if waxed daily; though I've never experienced a well prepared, multi-layered wax base turn white in a single day. (But I don't ski back East on icepack or race on ice.)
I find I need to go back to a softer, more absorbent wax layer (warmer weather or red warm prep) from time to time to get the base renewed, "wetter" again, and provide more adhesion for the stiffer mid and cold waxes that might be appropriate for the next day's conditions. Of course, you have to scrape and brush out each layer before adding the next.
This is something race prep guys would do routinely, multi-layering waxes; but maybe not recreational skiers.
Also, some waxes are more durable than others. The Briko-Maplus race base medium (Italian) lasts more than a full day of skiing - it's noticeably "wet" after one and usually two or more days (though I still somewhat compulsively wax after almost every ski day).
Food for thought.