Tell me about wet sanding.

[Rick Lee]

I cut down the stock windscreen on my bike today and painted it flat black. But I had some runs in it and needs to clean them up before a respray. Is that what wet sanding is for? What grit do I use and do I only sand the blemishes or the whole thing?

[9dreizig]

Rick, you might want to try the painting and body work section, nothing but sex starved gun nuts in this section ...

[Hugh R]

wet with lots of water using wet-dry sandpaper using a rubber sanding block not your finger tips, use 200 grit or finer, sand, wet, use the water to keep the pores of the sandpaper open and clean of scuz. The wet provides less sanding lines.

[9dreizig]

Uhm I meant sex starved gun nuts AND Hugh...

[911pcars]

Originally Posted by Hugh R

wet with lots of water using wet-dry sandpaper using a rubber sanding block not your finger tips, use 200 grit or finer, sand, wet, use the water to keep the pores of the sandpaper open and clean of scuz. The wet provides less sanding lines.

Hugh,
All is good except the missing zero. 2000 grit is more like it.

Water also flushes sanding grit away and prevents creating larger sanding marks in the paint.

Sherwood

[crustychief]

It also helps to add a drop or two of dishwashing detergent like ivory to lubricate the process.

[Rick Lee]

Do I really need 2000 grit and dishwasher soap? This is just the first coat of flat black on a lexan windscreen. Nothing fancy, but I want to get rid of the blemishes and then respray.

[Gogar]

Rick,

When i was painting my Honda plastics I used a wet-sanding sponge kind of thing I found at Home Depot, it's about the size of a sanding block. I think it was 350 grit. Worked pretty well.

When painting, do A few medium light coats, and then hammer it on the last one, and try your very best for no runs. If you get a run you'll have to knock it all the way down and kind of start over.

I think also it might help between coats to wipe with acetone, depending on what kind of paint you're using.

[greglepore]

You'd use 2000 to color sand - 320 is fine for removing runs. Just remember that runs take forever to dry fully...

[Laneco]

Gogar is right. You are not ready to wet sand. Wet sanding is not intended to remove runs...

To remove the runs you must either sand as suggested above or if you have good skill with your hands you can cut the runs down with a razor blade. Then sand the whole surface lightly with a less aggressive product and repaint using light coats.

My husband can cut runs off with a razor blade. I can only dream of this skill. For me, its sand down to uniform level, a light sand, then repaint...

angela

[ruf-porsche]

I would have painted the back of the windshield with the final color. If you ever raced RC cars that you have to paint the clear body you will know what I mean.

[Tim Hancock]

Rick, "wet sanding" is what one does when one has a large amount of sanding to do. It can only be done using automotive grade (I use 3M Imperial wetordry production paper) sandpaper. It is the stuff that is black. General use hardware store sandpaper will typically fall apart if used wet. In general, sandpaper clogs quickly when used dry, by continuously dunking "wet" sandpaper in water, it does not clog and will last longer before needing to change paper.

Your project is small enough that you don't really "need" to wet sand, but I always do as it is what I am accustomed to. Whether you wet sand or dry sand, you simply need to knock the runs down as Angela said. As you are going to respray, just have at it with maybe some 280 or 320 grit until you can't feel the runs, then go back over the whole thing with some 400 or 600, then repaint. Different paints/primer systems often have different requirements for sanding grit prior to topcoats, but if you use 600, you should be good to go with your rattle can flat black. Flat black from a rattle can is pretty simple to apply and you don't have to worry much about technique. First, lightly spray all edges, then go over the whole thing with a light coat. maybe 5-10 minutes later as the finish starts to dry and look flat, respray again with a medium type coat and you are done.

[targa911S]

Originally Posted by greglepore

You'd use 2000 to color sand - 320 is fine for removing runs. Just remember that runs take forever to dry fully...

Yup....320 is the way to go. Use 600 for your color coats, or before you squirt any clear. Dish soap optional, it just cut the surface tension and keeps the paper cleaner.

[Embraer]

if you have runs, and you're very careful, you can remove them with a razor blade. then procede as the previous posts said.

when i worked at a body shop, I was removing a couple of runs from a Ferrari 360. Being my first time doing it, i was nervous as could be. the painter came over and said "just do it...it's only a car. you're not going to die. if you goof up, i can fix it."

[Rick Lee]

A razor blade isn't gonna fix the spots where I tried to dab the runs with a clean paper towel. I need to sand the whole thing down, maybe not bare, but I need to get it even. Unfortunately, it's not supposed to be above 70 deg. for a while and will probably rain tomorrow.

[Gogar]

Originally Posted by Rick Lee

A razor blade isn't gonna fix the spots where I tried to dab the runs with a clean paper towel. I need to sand the whole thing down, maybe not bare, but I need to get it even. Unfortunately, it's not supposed to be above 70 deg. for a while and will probably rain tomorrow.

Poor baby. It's 5 degrees here, and I have to clean up some sheetmetal to send to the powdercoater.

Yeah, you'll probably sand it back down pretty far. Resist the temptation to use a power tool, the heat will mess things up.

[targa911S]

A heat lamp or a hair dryer may get you to where you need to be to sand it.

[Rick Lee]

I just sanded it down pretty far. It's been 24 hrs. since I painted it, but those thick spots were kinda gummy. Just shot it again with a coat of paint and I suspect it will be a while before it's ready for further coats, as it's getting colder here. No hurry though. I don't mind riding sans windscreen. Less buffetting that way.

[targa911S]

What did you paint it with lacquer or acrylic? Sounds like the latter. Try my heat lamp or hair dryer advice and sand it tomorrow.

[Rick Lee]

Rust-oleum semi gloss flat black enamel.