When it's raining, I like to slip a plastic bag down over the fletchings in my quiver. Nothing keeps a feather from getting matted down like never allowing it to get wet.

Bohning makes a petroleum based feather waterproofing liquid called Dri-Tite. It comes in a small glass bottle with an applicator brush. Just brush it on both side of each feather liberally, and allow to dry. It stinks like heck at first, but dries odorless within a day. That stuff works pretty well. I treat each of my arrows with it before (and sometimes during) the season.

I tried a silicone powder once that was aweful. You are supposed to place it in a plastic bag, then you stick the fletched end of your arrow in the bag and work the silicone into the feathers. My feathers came out caked with the powder and matted down like like had just gotten wet!

Sort of a side note, but if your feathers DO get wet and matted down, you can revive them. First bring them indoors and allow them to dry. Then boil water in a steam kettle. If you hold the feathers in the steam, the feathers will fluff out like new. Just don't hold them in the steam so long that they become soaked again. <img src=icon_smile_cool.gif border=0 align=middle>