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Problems getting a mirror finish (polyurethane spray can)


gar38
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This is my first attempt at finishing a guitar. This guitar is a Ibanez Gio. I have stripped and sanded, the wood, used a wood filler, sprayed a sanding sealer, and sprayed primer on the guitar. I then used the swirl painting method, and it turned out alright. I used Humbrol enamel paint. http://imgur.com/M5enLVM

I then began spraying Minwax Polyurethane clear gloss on the guitar. My original plan was to spray about 4 coats, let it dry over night, wet sand with 600 grit then 1500 grit (these are the only two high-grit papers i have; i could get more if it is prudent), and repeat that process, followed by a rubbing compound. Yesterday, I put 4 coats of poly on the guitar, about 2 hrs apart as per the instructions on the can. Today, I noticed that the finish really was not that shiny yet, and i figured 3 more coats wouldn't hurt. So I applied them and helped the body dry with a fan. Tonight, I started with some wet sanding, using the 600 grit. Now, I have heard that it's possible to sand through layers of poly and create these "witness lines," as they're called. I wasn't too concerned about this, as I'm really not expecting a factory caliber finish.

When I did a little sanding, I thought the orange peel would be smoothed out revealing a dull sheen. Unfortunately, this was not the case, and it seems that paint itself was coming off. As seen in this image, the gray primer is poking through the green paint where I sanded. http://imgur.com/DSVpPO7

So I stopped, and I came here. If anyone has read through this, I would be very grateful for some advice from an experienced person. Here are some more photos:

Some parts, like this side, looked pretty good: http://imgur.com/TOJACjW

Some parts have a real "orange peel" look to them, such as the inside of the horns: http://imgur.com/6rcs8FY

This is very frustrating as I treated all parts the same in terms of sanding.

Also, the face of the guitar in general just doesn't look very even as far as glossiness, and I really don't know why: http://imgur.com/HZu7jNw

http://imgur.com/fRZuJES

Again, thanks in advance for any advice anyone can offer. i want to get this guitar back in action by the end of August so I really don't want to be held up by the painting much longer.

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That looks very much to me like the paint and the clear are not compatable and the clear is desolving your paint. Check you paint's info and see if there is a certain amount of cure time recquired before applying a clear. Does it specify what kind of clear to use? Do a quick test and apply so paint to a scrap board and see if the clear causes the paint to wrinkle and bubble up like that. Is the surface hard or does it feel soft or like it wants to peel up. That is not orange peel; man it looks more like paint with paint stripper applied to it.

I hate to say it, but I fear you are going to have to strip it off and start over.....

SR

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Welcome onboard, gar38. I have to agree with ScottR....that is definitely some bad reaction between incompatible paints. Ideally you should always test your paint compatibility on scrap before committing it to the workpiece itself.

I think you'll need to strip back and start from scratch I'm afraid. That's not recoverable. If the poly is proving to be an issue, you either need to change the type of clear you're using or the paints you're swirling with. If you need it back in use by the end of August, you'll need paints that cure pretty damn quickly. Automotive two-pack (2k) cures faster than virtually anything and you should be able to acquire it in rattle cans. It is however a potent neurotoxin so cover all skin, get excellent ventilation and put your health over the workpiece.

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