My new WB has a scratch, what to do?

[gone_fishin]

600 grit will still leave an area on the face of the block/heatsink with microscopic grooves so that Artic Silver can adhere to. Those very small sand marks fill with ASlll and helps in keeping ASlll from being pushed out from the area.

Well wishes to you DV. The least amount of thermal interface material, ie paste thickness, is the ultimate goal. 600 grit is good but the thinner the tim joint the better in all calculations I have seen. As far as the ridges holding the paste longer, well that would be a longevity property to the tim as it is affected by thermal cycling. (I've been reading my issue of coolingzone magazine)