How Far To Sand?

[integra]

I was reading over ar reranch.com on how to finish with a solid colour and came across this...

(Note: If the old finish is a polyurethane finish you will have a difficult time completely stripping the finish back to raw wood. It is acceptable with poly finishes to sand the old finish with #220 dry and use the old finish as the base. If that is to be your direction skip ahead to the section on priming).

My question is, how far do I sand with the 220? How do I know when to stop? Thanks!

[Mickguard]

I'm guessing they mean that you're just trying to rough up the surface to give the new paint something to adhere to.

220 will barely cut into a poly finish, you'll see. It'll just scratch up. My guess is that once those scratches are uniform, you're good to go.

But you can strip the guitar further if you like-- take some 40 grit sandpaper to it, you'll be down to the sealer coat in no time. Works best with an electric sander--took me about half and hour to do my tele.

I suppose you could go all the way through to the wood, but getting through the sealer would take a lot more work.

[integra]

This method was appealing to me as it cuts out a few stages and simplifies things. It's my first refinish so I figured anything that makes it easier would be better! Would it be a better idea for me to completely sand the body down, or do you think this will be ok for my first project?

[erikbojerik]

If you're painting a solid color, by all means don't use anything heavier than 220 grit and don't go all the way down to the wood. 220 is just fine for the paint to adhere to, just make sure you have uniform 220-scuff everywhere on the guitar, no shiny spots. Be super careful around the edges of the body so you don't sand through all the way to wood. Then go with the primer and/or paint.

The only reason to sand all the way to wood is if you want to do a transparent finish that shows off the wood grain. But then you have to go through many other steps (fine-sand, maybe grain fill depending on the kind of wood, coats of sanding sealer w/sanding between, then primer/paint).

[integra]

Awesome, thanks! Sounds like something even I might be able to manage!

[gun]

Usually on guitar like a Fender Amercan Strat you can see under the color coat a polyester seal coat. Very thick. If you sand down the color coat and achieve an even surface without low spots as Erikbojerik said you before it's ok.

Primer then apply your color coat and clear.

[Doc]

Remember what you're doing here.

The best thing about polyurethane is that it is resistant to nearly everything, even paint stripper. The stuff you coat it with will not bite into it chemically. By sanding it you are putting a gazillion tiny scratches that the top coat can flow into and bond to. It bonds mechanically.

I would just sand the whole thing until it is uniformly dull, no gloss left anywhere.

Don't go coarder tahn 220 but don't go finer either.

Get all of the sanding powder out of the scratches before you start witht he new stuff. I've rushed this part before and paid for it when the finish lifts down the road.