The whole "black shavings" issue is interesting. Here's Zach Caldwell talking about it re hotscraping flouros.
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This photo of a thin strip of base materials shows the crystalline UHMWPE sinters as the clear areas. The black web of material around them is the amorphous material where base additives live, and where wax goes into solution.
...You can also use the “hot-scrape” method. This is an effective method of cleaning skis, but I don’t like it for a number of reasons. Specifically, I don’t like it for cleaning pure fluoros because the soft paraffins used can’t carry enough heat to get the fluoros to melt and mix. And further problems arise when you turn the iron up. If you use a hot iron on a soft, low-melt-point paraffin, it is very easy to destabilize the amorphous materials in the base. This will cause you to scrape black wax shavings. Very satisfying if you’ve somehow convinced yourself that you’re removing “dirt”. But that’s not what’s happening. You’re removing carbon-blacking, and whatever other additive materials are in the base. Once the base is destabilized in this way, it tends to stay destabilized, meaning that you continue to scrape black wax shavings, and the base is quick to “dry-out”, or show areas of a white filmy deposit in the high-pressure zones after skiing. This white stuff is fibrils of the low density PE material in the amorphous zones, and it shows up against the black base just the way the black additive materials shows up in the white wax shavings. Usually both are present."
http://www.caldwellsport.com/2012/02/removing-fluorocarbons/