Finishing Problem/question

[sinnmb]

Hey everyone,

Let me say the obvious, that I'm completely new to painting and finishing guitars. I bought a cheapo Dean bass to play around with and for recording, but the finish on it was boring so i decided to strip it and paint it.

Using guides from this and other sites I did all this and got up to the finishing stage where i hit a major snag.

This is a picture of the bass after repainting but before finishing, all of the paint was done with rattlecans that are enamel.

When I sprayed it with a oil-based polyurethane finish (also rattlecan), i was apparently a little overzealous, as a got major runs in a few places, but even where i put on a smooth coat, it still turned the white parts to a dingy yellowish color... What did i do wrong?

From what I gather most people don't like spray cans too much, but i refuse to spend more $ on the paint job than I spent on the bass (80 bucks)

Any help would be appreciated and I appologize if this was covered somewhere i didn't see...

Edited October 9, 2005 by sinnmb

[unclej]

you didn't do anything wrong..well, other than the runs. most polys have a yellowing or ambering effect. it's just the nature of the beast. most varnishes and shellacs have the same yellowing effect. your real problem will be removing it without damaging your color coats..which look great by the way.

someone may come along with a better suggestion but all i can say is let the poly cure for a month or so and then sand out the runs and re-shoot it using lighter coats.

by the way, what kind of paint did you use to lay down the color? there's a chance that you could remove the poly without effecting the color coat.

good luck.

[Setch]

Poly over enamel is a bad idea, though you may get away with it - if you're lucky. Basically, and hard finish over a softer finish is asking for trouble, and poly is harder than enamel.

The problems come when the softer finish shrinks, and that cause the hard coating to crack, and/or delaminate in big sheets.

[Mattia]

The only non-yellowing finishes I know of are waterbased finishes (Target USL, Grafted Coatings KTM-9), and certain polyesters and polyurethanes, although that's generally the autobody stuff, near as I can tell, not the home improvement centre rattlecan poly. 'Polyurethane', after all, includes a very, very, very broad range of different finishes.

[Maiden69]

The only non-yellowing finishes I know of are waterbased finishes (Target USL, Grafted Coatings KTM-9), and certain polyesters and polyurethanes,

All 2 part poly are non-yellowing and crystal clear! Also most of the nitros, at least at time of painting... they do tend to yellow with YEARS of exposure. DEFT, is a non-yellowing nitro clear coat, the one with white can and blue letters! The othe one that is sold is yellowing and the can says it!

[sinnmb]

Hey everybody,

Firstly, thanks for the replies, although I'm hearing some mixed responces. I've decided the current paint job is a lost cause, i'm just gonna sand it down and start over.

So, is there any non-yellowing glossy finish that doesn't require a separate spray gun. I totally don't care if its varnish, poly, whatever.

[Mattia]

Hey everybody,

  Firstly, thanks for the replies, although I'm hearing some mixed responces.  I've decided the current paint job is a lost cause, i'm just gonna sand it down and start over. 

 

  So, is there any non-yellowing glossy finish that doesn't require a separate spray gun.  I totally don't care if its varnish, poly, whatever.

←

KTM is apparently brushable (Waterbased stuff), but I have zero experience with applying it that way.

[Doc]

The Minwax acrylic poly is a widely available nearly crystal clear finish that will go over most enamel. It comes in rattlecans and regular brush grade.

There are plenty of "water white" lacquers available some which will go over paint and some which won't. They are all dead clear and stay that way. Look in your yellow pages for a cabinet makers supply company and ask for their advice. My supplier stocks rattlecans of the stuff.

You might look into a cheap spray rig. I've got a gravity feed HVLP gun that cost me about $35.00 at an automotive paint shop, and while it's certainly not as good as my $400.00 Binks it does the job in a pinch. I use it when I've got colored finish to shoot at the same time I'm shooting clear to save clean-up time.