How To Control Sandthroughs?

[slor]

That's the million-dollar question, no doubt. I'm refinning an early '70s P-Bass. The color was great, and I had a good 4 - 5 coats of clear on top. I found a couple of specks of lint, VERY carefully sanded them off, and resprayed clear. Even so, the small sanded areas are a different shade under the new coat of clear. So I resprayed color, and now am building the clear back up, being extra-extra careful about lint.

All good. But now my clearcoating schedule is shot; instead of having 4 or 5 good coats of clear, I'm back to square 1 in terms of final polishing, right? Is there something I should be doing differently?

Many thanks,

Seth

[erikbojerik]

(1) What grit sandpaper are you using to sand out the lint?

(2) What kind of clear coat are you using....and if its not nitro, are you scuff sanding between coats? (and with what grit)

(3) Are you using spray cans or shooting with a gun?

Edited September 21, 2007 by erikbojerik

[slor]

(1) What grit sandpaper are you using to sand out the lint?

(2) What kind of clear coat are you using....and if its not nitro, are you scuff sanding between coats? (and with what grit)

(3) Are you using spray cans or shooting with a gun?

Thanks for the reply:

(1) 600 grit, well soaked

(2) ReRanch clear nitro

(3) Rattle can

This morning as I inspected the guitar before the first spraying, it occurred to me that any sanded area has a different appearance from its surrounding, even if it hasn't been sanded through to the color coat. Even under a new coat of clear, it will have that different appearance until the whole guitar is polished back to that "sanded" color tone.

So it's possible that I overreacted in respraying color over the sanded areas. But maybe not; it would be terrible to get to the polishing stage and find that those different-colored sanded areas really WERE a different color, and you'd have to start again from scratch. Any thoughts?

Thanks much,

Seth

[erikbojerik]

First thing...anything from a rattle can will lay down as a thin coat. Quite a bit thinner than from a gun, so keep that in mind when levelling.

With nitro you don't necessarily have to sand between coats, as the coats will melt into each other. But yeah, if you sand some places but not others, then you may see some differences.

So whenever you scuff sand, you need to do it everywhere.

[Maiden69]

Well, 600 is a bit rough for the wet sanding. And 4-5 coats of can nitro, well that is too thin to begin with. If I'm using nitro from a can, I use about 3 cans before I do any wet sanding, and that is about 15-20 triple pass coats.

And then I will begin with 800 depending on how bad was the surface at the time. And after I wet sand it nice and smooth I shoot one more pass, med-heavy. If you are good with the can, this last pass will look nice and smooth with no orange peel and after about 2-4 weeks you can start to polish. If the finish is not smooth you can start with 1500 grit paper and up.

[slor]

Well, 600 is a bit rough for the wet sanding. And 4-5 coats of can nitro, well that is too thin to begin with. If I'm using nitro from a can, I use about 3 cans before I do any wet sanding, and that is about 15-20 triple pass coats.

And then I will begin with 800 depending on how bad was the surface at the time. And after I wet sand it nice and smooth I shoot one more pass, med-heavy. If you are good with the can, this last pass will look nice and smooth with no orange peel and after about 2-4 weeks you can start to polish. If the finish is not smooth you can start with 1500 grit paper and up.

Hmm...yes, that's more clearcoating than I was planning on doing (I was thinking more like 9 coats, as per ReRanch's suggestion).

Even so, I only chose to sand after 4 - 5 coats to get rid of lint, not as a final or intermediate polishing....

Thanks,

Seth