Wet Sanding?

[Futsal Fred]

I know this question will make me sound like an imbecile but I simply can't find anyone who can give me an answer, so here goes:

Why do people say to wet sand as opposed to just grabbing sandpaper and having at it?

I'm removing a thin layer of primer that the stripper won't budge and I sure don't want to mess anything up but it's not like I'm grinding away on a thicck layer of paint or something.

I guess I'm saying I just don't understand the reasoning.

 

[Ross]

Wet sanding helps to wash the loose particles away from the sanding area and keep the sandpaper from clogging. you can use water or mineral spirits or any of the finishing oils.

 

[jimmyb]

+1
and if you choose to wet sand, make sure you get good paper suited for wet sanding. most others will fall apart almost immediate when soaked with water.

 

[s sauer]

Wet Sanding

I typically wet sand the hard vinyl racing bottom paint to reduce build up each year before the new coat of bottom paint and after that coat to get the smoothest surface finish for least drag.

However, in your situation, if you want to have best control of your sanding, a pair of hard rubber 3M sanding block and say #320 grit wet-or-dry paper used with a bucket of water with a couple drops of dish washing liquid will allow you to carefully remove the paint and more easily see your progress.

If you want faster more aggressive removal, try #220 grit wet-or-dry.
A courser dry sandpaper, say #120 grit would remove the paint even faster but would leave deeper visible scratches in the surrounding material. For less critical surfaces such as a heavy build up of bottom paint you can start with coarser grit paper, maybe 60 or 80 grit, then switch to finer 120 grit and on to wet-or-dry finer grit for the finishing touches.

Another reason to go the wet sanding route is to control dust. Theoreticaly you can spread burlap under your wet sanding area and catch a good portion of the wet paint residue. Don't know if this is more or less than a dry orbital sander with a vacuum attachment, but as said earlier , wet sanding by hand also keeps the paper from clogging up, and allows you to go slower and more controlled to see your progress.

 

[Ross]

Re: Wet Sanding

For bottom paint sanding I use the 120 or 80 grit mesh drywall sheets and a drywall sanding pad and pole and a five gallon buctet of water. I never use anything that course where scratches will be a problem.

 

[Ray Bowles]

Fred, This might be too basic but I'll do it anyway.
Dry sanding is just that. You sand whatever you're working on with sandpaper. Lots of dust and you can see what you're doing as you do it.
Wet sanding done after dry sanding has removed the bulk material. It is where the area to be sanded has been wet down and you use only sandpaper that is rated for wet sanding. This paper is usually black or dark. The water or other lubricant is applied to the area and paper. You add more moisturizer as you work to rinse away the removed material. Wet paper comes in standard sizes and in very, very small grit size like 1500 to 2000 grit.
Wet sanding leaves a perfect surface to then be painted or finished.
I hope this helps but please forgive this note if you already know what wet sanding is.
Ray

 

[Joe]

I just finished a bottom job on my boat... wet sanded with drywall screens... piece of cake... The absolute, very best reason to wet sand is that you don't have to hook up all the protective gear, scavenging equipment and boat skirting required by boatyards.

 

[Ross]

if you are planning to paint don't sand finer than 120 grit paper. You need a little tooth for the paint. With varnish between coats 220 grit is fine enough. Above 400 grit you are poliishing and 600 grit and finer delivers a mirror finish. For sharpening tools I often go as fine as 4/0 emery paper for when I need a scary sharp edge.

 

[tommays]

Sometimes you need to wet sand to see when your done

For example on Awlgrip 545 primer is you dont sand until the water stops beading the next coat will fail so wet sanding is a handy to do it

 

[Barnacle Bill]

Also with wet sand paper you can use pneumatic tools while it is not a good idea to use electric tools with water. Could be a shocking experience which might lead to sailing into the sunset for the last time.