I think I know why, but....

Discuss custom painting, artwork and airbrushing



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PostPosted: Sat Feb 01, 2014 10:42 am
Hi.
I'm a newbie here, from the UK.
I'm a massive fan of JoAnn's work, have the books and have read them cover to cover. Thanks JoAnn for all of the information, it's worth its weight in gold.

Now, probably what I'm asking here could just as easily be posted elsewhere on this forum but since what I do is primarily custom work here goes.
I recently painted an acoustic guitar. It had been knocked about by its previous owner and so I had had to repair it in various places. having flatted everything smooth, I primed it using Upol high build primer, a rattle can I know, but for the small volume required (and given that it's always gonna be sanded) I generally use canned primers. I flatted that smooth and then sprayed the whole deal with Auto Air basecoat sealer black. Once that was done and heat cured I sprayed four light coats of AA black base. I waited for all of that to fully cure before shooting two coats of 2k clear over the lot, just to seal the basecoat and prior to airbrush work. A few days later I flatted the clearcoat with 1200 and began airbrushing the required artwork on the front of the guitar. After about, oh, forty or so hours of airbrushing, the job was ready for final clearing. At this point I realised that I was running low on my usual 2k product and so I phoned the local supply store and asked them to get me some more. They told me they'd ring me back when it was in, but I heard nothing. About two weeks later I called by and was told that they couldn't get the usual stuff but had a really good replacement that they sold tons of and that I'd not be disappointed with. I asked if it was the same flash off time as the other one (2-3 minutes) and was told yes, it was.
Note; first schoolboy error; alwasy get a tech sheet.

I went home, mixed up a small batch, remember it's only a guitar here, and sprayed three coats over the lot. At the time I was spraying I thought it looked very wet and I spotted the odd sag here and there, which is unusual for me as I'm usually pretty tidy that way. After about ten minutes or so the cracks started to appear here and there. Thoroughly unimpressed, I shut everything down and left it to go back the next day to see what needed repairing. Huh. Repairing eh? How about the whole thing?!! I know some of you will have seen this coming and I apologise to you for the length of the post, but if it saves som eother poor soul from doing this same thing then it's worth it!

I began flatting down the mess and the paint began rolling under the paper. It was soft.
I eventually took the lot off using a low heat gun and a scraper. Start again with a fresh canvas.

Now, I think that I applied the clear too heavily and too quickly. All the tech I can find on Omi Cron says 10 minutes flash off time, not 2-3. I think, what happened was that the solvents in the excessive amounts of wet clear went down into the basecoat and artwork and softened the lot before crazing and cracking as it all eventually dried. Needless to say, I will go back and grab a tech sheet for the new lacquer! But, am I right in my theory of what went wrong?

Sorry again for the length of time it's taken you to read this. If only I'd stuck to JoAnn's words of advice.......

"Know your clear".

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PostPosted: Sat Feb 01, 2014 6:23 pm
Sorry to hear that! The new clear you used, did you mix it correctly? And yes, if you only allowed 2-3 minutes flash between coats you can have issues like that. Even if the sheet said 3 minutes I'd give that first coat 15-20 minutes just to let it lock down and outgas enough before the next coat.



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PostPosted: Sun Feb 02, 2014 5:18 am
Thanks Chris, I'll make sure I do that when I redo the job. I'm finding that you never stop learning doing this. Like so many things!

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PostPosted: Mon Feb 17, 2014 7:08 pm
Hey, BKM was that AA black base you used Auto Air Colors by any chance? Just curious????
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PostPosted: Tue Feb 18, 2014 1:52 pm
DarrelK wrote:Hey, BKM was that AA black base you used Auto Air Colors by any chance? Just curious????


If it's Auto Air, the problem is probably because your first coats of clear were too heavy. Using Auto Air Colors, your first two coats of clear are very light mist coats, with 1/2 hour or more between coats. This allows the clear to crosslink with AA.
Third and subsequent coats are sprayed like you normally would.

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PostPosted: Tue Feb 18, 2014 11:31 pm
Yep, Ed that's where I was headed with that question.... :wink:
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PostPosted: Sat Mar 29, 2014 6:20 am
Sorry guys, yes, it was Auto Air and you're absolutely correct in saying that I was too heavy on the coats. I was also too fast! Like waaay too fast. I had been using a different clearcoat prior to the new stuff and the timings were massively different. :whoops:

Absolutely with Auto Air, and I imagine many water based paints, you have to do two or maybe even three dropcoats before you can start getting heavier for some depth and shine. As I say, always a learning curve.
Thanks guys.

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