Does it matter if you wet or dry sand?

[Weslicon]

I was wondering if it is neccesarry to wet sand or dry sand. Is one superior to the other? what are the differences?

 

[StevePerv]

In general, the more poreous the material, the less likely I'll wet-sand. Wet-sanding is preferable only because it keeps the dust out from in between the grits (reducing the effectiveness of the paper/block). But in situations with poreous materials like bondo, the extra moisture will cause all sorts of problems. Mainly it gunks up the bondo and roughs up the finish. Wet-sanding will cause you to be faster, but yields in more issues with poreous materials.

Just depends on what you'd like.

 

[misfitjh]

You generally only wet sand paint and that's just to get the orange peel out and smooth it down before spraying your clear coat. If you going for a fresh off the factory floor kind of look then wet sanding will help. If you going for that dragged through hell look then wet sanding is a waste of time.

 

[hollywood]

Just another tidbit,
If you sand through to your pep paper and did not seal it really good with resin, and then try to wet sand it, the pep paper will wic the water in and make a tracking bubble under your bondo layer. This can result in sudden big potholes in the nice smooth bondo you've been spending so much time sanding. I had literally a one inch circle just flake right off, all the way down to the fiberglass layer because of that.