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| One more nitro question... http://www.luthiersforum.com/forum/viewtopic.php?f=10101&t=48509 |
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| Author: | meddlingfool [ Tue Nov 08, 2016 3:26 pm ] |
| Post subject: | One more nitro question... |
Is it common for the topcoat of nitro to chip or delam from the base coat? I was sorta under the impression that the topcoat melted and burned in to the basecoat to form a single film thickness... |
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| Author: | Josh H [ Tue Nov 08, 2016 4:09 pm ] |
| Post subject: | Re: One more nitro question... |
No that is not common. The only thing I could think of would be some kind of contamination between coats. What are you doing for sanding between spraying sessions? |
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| Author: | Freeman [ Tue Nov 08, 2016 4:32 pm ] |
| Post subject: | Re: One more nitro question... |
I have had the entire finish chip and come off of the wood itself when I just shot a thinned coat of lacquer as the seal coat. This only happened where I've drilled holes thru the finish - strap buttons or similar. Since I've been using vinyl sealer that hasn't happened. 
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| Author: | bluescreek [ Tue Nov 08, 2016 5:34 pm ] |
| Post subject: | Re: One more nitro question... |
if you sanded your body too fine this can happen looks ling the finish is not adhering. I don't sand past 220 grit |
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| Author: | Jim Watts [ Tue Nov 08, 2016 6:45 pm ] |
| Post subject: | Re: One more nitro question... |
I would say it's not common, however it is brittle, so don't over tighten your tuners. |
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| Author: | meddlingfool [ Tue Nov 08, 2016 8:17 pm ] |
| Post subject: | Re: One more nitro question... |
I see, I see... And if you had a nitro topcoat sprayed onto a UV polyester base coat, would that seem more plausible? |
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| Author: | B. Howard [ Wed Nov 09, 2016 7:03 am ] |
| Post subject: | Re: One more nitro question... |
Prepwork......that is where 80% of delamination failures come from. As John stated sanding too fine is a cause of this as is not cleaning away all the sanding dust prior to spraying. Having gone over a UV base-coat you should have been able to sand to 600 and have nitro adhere quite well..... In this case I believe you may have too much dry film build. That finish looks really really thick at that chip....maybe 20 mils? Nitro, especially the modern formulations, get more stiff and brittle as thickness increases and then become more prone to crazing and chipping and adversely affecting adhesion . |
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| Author: | klooker [ Wed Nov 09, 2016 8:10 am ] |
| Post subject: | Re: One more nitro question... |
Just trying to get this straight. The base coat was UV cured polyester and the nitro separated from it, or a previous layer of nitro? Kevin Looker |
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| Author: | Freeman [ Wed Nov 09, 2016 11:06 am ] |
| Post subject: | Re: One more nitro question... |
B. Howard wrote: In this case I believe you may have too much dry film build. That finish looks really really thick at that chip....maybe 20 mils? Nitro, especially the modern formulations, get more stiff and brittle as thickness increases and then become more prone to crazing and chipping and adversely affecting adhesion . Brian, this was a different guitar than the OP's - it was sanded to 320, had an alcohol stain applied to the wood then the first coat was thinned (probably 1:1) nitro, followed by some color coats and then clear. I was simply trying to show that the entire finish cracked when I drilled the strap button. I agree, wrong prep and too much finish. Don't want to confuse Meddling's original question. |
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| Author: | meddlingfool [ Wed Nov 09, 2016 11:32 am ] |
| Post subject: | Re: One more nitro question... |
Just trying to establish if a nitro topcoat will burn into the basecoat forming a single film thickness. |
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| Author: | Glen H [ Wed Nov 09, 2016 11:52 am ] |
| Post subject: | Re: One more nitro question... |
It will if the basecoat is also nitro. |
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| Author: | meddlingfool [ Wed Nov 09, 2016 1:16 pm ] |
| Post subject: | Re: One more nitro question... |
So, if you had a nitro top coat that was separating from the basecoat in distinct layers, would you perhaps consider that the basecoat might be a different material than nitro? |
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| Author: | Glen H [ Wed Nov 09, 2016 3:46 pm ] |
| Post subject: | Re: One more nitro question... |
Personally, me, yes I would. Either that or there was some contamination on the "base" layers .... wax, polish (w or w/o silicone), skin oils. |
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| Author: | Jim Watts [ Wed Nov 09, 2016 4:57 pm ] |
| Post subject: | Re: One more nitro question... |
I'm on board with glens assessment. |
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| Author: | meddlingfool [ Wed Nov 09, 2016 10:18 pm ] |
| Post subject: | Re: One more nitro question... |
Thanks folks... |
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| Author: | klooker [ Thu Nov 10, 2016 7:16 am ] |
| Post subject: | Re: One more nitro question... |
Did you test what it separated from to see if it was nitro or polyester? Cured polyester won't dissolve with lacquer thinner, will it? |
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| Author: | meddlingfool [ Thu Nov 10, 2016 11:11 am ] |
| Post subject: | Re: One more nitro question... |
Too late to find out for certain, as all the chips are gone. Ah well. |
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