Just making sure...

whitebison66

Senior member
Messages
777
I've read through the posts I could find about sanding, drying, and buffing nitro. I've just finished putting (rattle-can) coats on the face of the Less Paul project. Probably 6-10 coats, some of them heavy. Wet-sanded (scuffed, really) w/320 between.

The way I understand it (and please correct me if I'm wrong), there are 3 things that need to be done, and they need to be done in this order:

1: (Wet) level-sand @ 600 grit, removing all dips, etc. Doing it now is apparently easier than when the lacquer hardens after the drying period.
2. Let it dry for at least a week, preferably 3 (which is what I intend).
3. Buff with compound, and/or wet-sand through higher grits (800-2000, according to varied posts). I'm doing this one by hand, so I know what I have ahead of me.

I am asking you all now if this is the preferred order of these events. It makes a lot of sense to me, but I want to double-check.


Thanks!
 

Patrick from Davis

Senior member
Messages
2,197
Load up with 6-10 coats first, and give a week or so between coats.  You can smell when the solvent is gone, then put a new coat on.  Wet sand flat (or smooth if the body is not "flat") and then add another 2-3 coats.  You have to level it before adding the last coats.  If you don't it will not polish correctly and you will see remnants of drips and what have you when you polish.  After the second set of coats are applied, wait at least three weeks for it to dry and start to shrink and harden.  I rushed this step and learned the hard way it is a bad idea.  After the wait, you wet sand going from 320 on up.  Be very careful at this point, it is easy to sand through things.  After that is done, time to polish.  If you have not waited, the polish rag will dent the finish because it is not hard enough and leave marks.  Really pisses you off in my experience.  Keep polishing until it looks good to you. 

You can use turtle wax car polish
You can wet sand with Formby's lemon oil
You should wash between each step with naptha or risk the layers not melting together correctly

I hate to say it, but you will find something to mess up.  Hopefully you have minor issues and do not do some of the stupid things others, meaning me, have done.  Good luck.
Patrick

 
W

Watershed

Guest
Hey,

I agree with Patrick, sand it smooth (watch the edges), then add a few more coats of clear, then wait.  I have sanded through (to the color, metallic) and it really is infuriating.  I have definitely added grey hairs from it.  I really don't spare on the clear now.

I'll admit to stupid stuff too.  The biggest one was chipping at the neck pocket during final assembly.  If the neck pocket is tight putting the neck in, it will probably chip on the way out.  Make sure the neck pocket is free of paint.  It really doesn't take much to chip it.

Good Luck,

James
 

Keyser Soze

Senior member
Messages
206
Nitro always sands better after extended drying.  It is not as soft/gummy and will not load up the sandpaper.  Heck that principle applies to most any finish.

The main reason most people don't allow a full cure before intermediate level sanding is time considerations.  Assuming you have properly grain filled (if necessary) then there is no real danger of creating a relatively level surface for application of final topcoats followed by final sanding and polishing. 

(if you have not properly grain filled then a not-fully-cured topcoat - even one sanded glass smooth - may later shrink back to reveal wood grain/pores)


Although, speaking in absolutes, with nitro intermediate sanding is not absolutely necessary. 

Nitro is a finish that 'burns in' meaning that each successive application slightly dissolves the prior layer and they meld together to become one mass. If you have applied enough finish to avoid the risk of sanding through to tinted/color coats/stained wood, and allowed the finish to dry to the point where it will respond well to polishing (soft nitro may sand ok but it will turn to a gummy hazy mess when hit with a polish loaded buffer or pad)  then you can actually level sand then continue right on to fine sanding and polishing without any additional coats.

However be aware that what can happens is, after waiting the whole month for proper drying, and during the course of level sanding you find that what you swore was a super-duper even application of nitro really wasn't quite so super-duper evenly done and you will need to apply a couple more coats (and wait another month before final sanding/polishing.)

So many people simply accept the 'extra' two weeks from intermediate sanding and planned application of top coats rather than risk getting the occasional one month setback.

When you use other finishes that don't burn in (e.g. poly or cured acrylic) then level sanding creates witness lines.  Polishing will not eliminate witness lines.  The only way to hide them is with application of  additional coat(s) that will not be heavily sanded (else you may get more witness lines.)
 

whitebison66

Senior member
Messages
777
Okay, a new question for the same project...

The guitar has been hanging in an air-conditioned room for almost 4 weeks.

Just today I wet-sanded the dried nitro (did the fingernail test, etc.).

I started at 600 and went to 8000/1 micron (I had the paper, and what else is it there for?)

Finished with Swirl-X. It only took me a couple hours (it's a mini-guitar), and I am pleasantly shocked at the clarity and smoothness of the finish.

My question is, how long should I wait before

A) Applying wax

and

B) Installing hardware like tuner bushings, pot, switch, and bridge posts (Gotoh 510)?



As always, thanks!
 

Patrick from Davis

Senior member
Messages
2,197
If you have polished it, it should be good to go.  Step one, and this is a biggie, take a picture now.  This usually means Karma will work out on your side.  If you do not have a picture, oh geez...  It should be fine to do the rest of the assembly to it.  If you are feeling patient, wait for the wax, but other than that, it sounds good.
Patrick

 
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