Q About Spray-on Polyurethane

[Paul Marossy]

Does polyurethane not like spray paint? I mean, is it normal for it to peel off of something that is spray painted?

[Maiden69]

Paul you just beat me to this thread. I was about to post a new one in the same reference.

DO NOT USE OIL BASED POLYURETHANE PAINT.

The paint I used was Olympic poly oil based and I just got a can of minwax water based and it sucks to be applied.

Or water based for that matter, the water based is a bit better for painted surfaces but the oil is not.

I just finished my blue guitar, and it painted like a dream, nice flow almost easy to color sand, buffed hard but to a beautiful shine. After my son hit the guitar this morning with his new cycle a white circled formed. I thought it was a scratch so I rubbed it and it turned bigger. Now the hole fron of the guitar is without clear, it peeled like a snakes skin, no residue or anything. I think I will have to use a wax and grease remover before painting again, because the paint feels smooth kinda oily.

[erikbojerik]

I've used Minwax Fast-Dry polyurethane (rattle cans) for the clear coat on all my guitars. Sometimes directly over sanding sealer (natural finishes), sometimes directly over Krylon spray paint (also from rattle cans). The regular fast-dry polyU is oil-based; the fast-dry polycrylic is water based (I've never used it; it is not as clear as the oil-based and doesn't cure as hard).

I've never had it peel over Krylon (or sanding sealer for that matter); I let the Krylon dry a week before applying the polyU. It goes on pretty thin, so you need many coats, an entire can for one guitar body. I lay the body flat (I mean level, spray on a coat as thick as it will go on without running, wait 20 minutes until its tacky, then flip and do the other side. Repeat for 5-6 coats. I let the polyU cure a month before even thinking about buffing out.

I've had it peel over previously-cured poly layers (over spots that I missed roughing up), but never over Krylon.

[Paul Marossy]

After my son hit the guitar this morning with his new cycle a white circled formed. I thought it was a scratch so I rubbed it and it turned bigger. Now the hole fron of the guitar is without clear, it peeled like a snakes skin, no residue or anything.

Yeah, I had a similar experience.

What about spray lacquer? Is that any good for finishing guitar bodies?

[Maiden69]

I haved used about everything available but 2 part poly. I had good experience with Duplicolor, but if you spray it too thick it will take ages to dry, and I loved the way the Krylon triple glaze covers, but again it's not too heat loving since this, and this, happened with only sun light. It bubbled up like about 1/2" high. And it's a pain to polish. The end result is nice shines, is hard and you can achieve this with less coats than nitro.

And poly I tried because I was looking for an alternative. In a scrap piece it turn out great, so I did the guitar and that happened.

Right now, I'm using DEFT to finish the guitar I'm making. So far so good, the only problem I see is that it takes a lot of coats to build up nicely, but the coats dry faster, and there is less orange peel present than with the Dupli. This one have only 2 thin coats (about 3 passes per coat) on it to seal the color and it 's hard and there are almost no fume smell in about 24 hrs. Nice, I only see it harder to polish, but only time will tell.

More updates on my thread.

[ddgman2001]

I've used Minwax Fast-Dry polyurethane (rattle cans) for the clear coat on all my guitars.

Repeat for 5-6 coats. I let the polyU cure a month before even thinking about buffing out.

How does it wear?

Compared to lacquer, how does it stand up to fingernail scratches?

I've been thinking of using it for satin finishes.

[erikbojerik]

It does set up pretty hard, when it's fully cured you can't dent it with a fingernail (my personal scratch test). But because you're basically applying one thick coat, you really need to let it cure much longer than it says on the can.

I use Drak's sniff test...put the body in an enclosed room and let it cure; if you still smell something when you sniff it, it's not done yet.