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 Post subject: Checked/Crazed Nitro…
PostPosted: Wed Sep 15, 2021 10:58 am 
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Brazilian Rosewood
Brazilian Rosewood

Joined: Wed Feb 20, 2008 7:15 pm
Posts: 7219
First name: Ed
Last Name: Bond
City: Vancouver
Country: Canada
Focus: Build
Status: Professional
Is there a fix for this? I seem to recall if you spray x substance on, you can remeld the nitro…?


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PostPosted: Wed Sep 15, 2021 11:51 am 
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Koa
Koa
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Joined: Sun Jun 22, 2014 1:45 pm
Posts: 1445
First name: Michael
Last Name: Colbert
City: Anacortes
State: WA
Focus: Build
I remembered this from Frets.com

http://www.frets.com/FretsPages/Luthier ... ator1.html

Pretty amazing results!

M


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PostPosted: Wed Sep 15, 2021 12:15 pm 
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Brazilian Rosewood
Brazilian Rosewood

Joined: Fri Aug 19, 2005 4:02 am
Posts: 3227
Location: The Woodlands, Texas
First name: Barry
Last Name: Daniels
It would be useful to have some more details of what you are working on. New finish or old?

I crazed a nitro finish once due to drawing in freezing air into the shop. I sprayed several coats of straight lacquer thinner and it softened the finish enough to heal the cracks. This was a super thick finish consisting of about 25 coats on a large desk project.


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PostPosted: Wed Sep 15, 2021 1:23 pm 
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Brazilian Rosewood
Brazilian Rosewood

Joined: Sun Mar 30, 2008 8:20 am
Posts: 5924
George Grotz, in his book "The Furniture Doctor" Talks about rebrushing lacquer furniture, which can work well on furniture that is built from thicker stock than guitars. Depending on why the finish checked /crazed it might be possible to do this and not have it check/craze again. Instrument lacquers generally have more plasticizers than typical furniture lacquer, so if it was originally sprayed with furniture lacquer it may check/craze again. Some catalyzed finishes cross link and may not react well to being re-amalgamated using solvents.
It's probably worth trying if the alternative is stripping and refinishing anyway.


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PostPosted: Wed Sep 15, 2021 3:23 pm 
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Brazilian Rosewood
Brazilian Rosewood

Joined: Sat Jan 15, 2005 12:50 pm
Posts: 3867
Location: United States
Keep in mind that nitro is not a finish for the ages. It's the little brother to a high explosive, and one molecule out of every six or so is unstable. All it takes is some time, or a bit of UV light and it will convert into water, CO2, and an oxide of nitrogen, which then reacts with water vapor to form nitric acid. If you remove one brick out of every six from a wall, what happens to the wall? Over time nitro shrinks and cracks, and the more of it there is the quicker this happens: think celluloid pickguards and binding, and nitrocellulose movie film.

There are solvent based 'amalgamators' that will penetrate into the checks and melt everything together. This doesn't make the finish any less unstable in the long run. Using something like that on any instrument that could be in any way considered 'vintage' will hurt the resale value down the road. Remember that nobody thought about the 'vintage value' of those old Martins and Fenders and Les Pauls back when they built them. They used a finish that was ultimately ephemeral because they were focused on mass production and the short term bottom line, not on making a 'work of art'.



These users thanked the author Alan Carruth for the post: jonnyfifield (Sat Sep 18, 2021 11:21 am)
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PostPosted: Wed Sep 15, 2021 3:42 pm 
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Brazilian Rosewood
Brazilian Rosewood

Joined: Tue May 13, 2008 10:44 am
Posts: 6232
Location: Virginia
I've had to use Blush Eraser a few times before and I believe that works by re-melting the Nitro.


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PostPosted: Wed Sep 15, 2021 10:39 pm 
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Brazilian Rosewood
Brazilian Rosewood

Joined: Wed Feb 20, 2008 7:15 pm
Posts: 7219
First name: Ed
Last Name: Bond
City: Vancouver
Country: Canada
Focus: Build
Status: Professional
Thanks…


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PostPosted: Fri Sep 17, 2021 8:13 am 
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Contributing Member
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Joined: Sat Jan 31, 2009 8:50 pm
Posts: 2246
Location: Seattle WA
Focus: Build
Status: Semi-pro
Let us know how it works out. I've got one that I've been debating something like that also. However, it's very fine and even and only visible at certain angles. It actually looks pretty cool LOL

Not sure exactly how, but I think it happened when I left it in the garage when I was reworking the shop and it got close to freezing...

Pat

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Pat


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PostPosted: Fri Sep 17, 2021 10:53 am 
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Brazilian Rosewood
Brazilian Rosewood

Joined: Wed Feb 20, 2008 7:15 pm
Posts: 7219
First name: Ed
Last Name: Bond
City: Vancouver
Country: Canada
Focus: Build
Status: Professional
This happened from culture shock. On the ‘nicest’ guitar I’ve ever made. I’m trying to convince him to just leave it be.


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