I think waxing maybe. When I pine tarred my skis I just hit the stuff directly with the flame with a flame spreader. Same technique as making creme brulee. Or maybe I was doing it wrong. (And the wax I just rubbed in.)
I just googled bonna 2000--they're asking 3 times more for those skis than I paid for them new. Even allowing for inflation it seems high. Of course asking isn't getting.
Bookmarks