Nitrocellulose issue

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blackalex1952
Blackwood
Posts: 777
Joined: Tue Aug 27, 2013 6:36 pm
Location: North East Victoria

Nitrocellulose issue

Post by blackalex1952 » Fri Dec 04, 2020 9:17 pm

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I have a problem with respraying a guitar I sprayed a year ago. This build has dragged on and seems jinxed!!! There is a lot of crazing of the old finish, I sanded it back, perhaps not enough, applied a highly diluted flash coat then resprayed with my usual lacquer mix . I use Nitrocellulose. Opinions and advice most welcome! Cheers Ross
"Everything I say on the topic is based solely upon inexperience and assumption!"

simso
Blackwood
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Location: Perth WA

Re: Nitrocellulose issue

Post by simso » Fri Dec 04, 2020 11:56 pm

Once nitro has cracked and split you really need to remove it back to bare wood to get a smooth finish again
Steve
Master of nothing,

Do your own repairs - http://www.mirwa.com.au/How_to_Series.html

Jim watts
Myrtle
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Re: Nitrocellulose issue

Post by Jim watts » Sat Dec 05, 2020 10:01 am

You might try a solvent called Cellosolve. I believe blush eraser is Cellosolve, but you'd want to verify that.
Here's a link to Frank Fords excellent site on how he used it on an old crazed Martin.
http://www.frets.com/FretsPages/Luthier ... ator1.html

blackalex1952
Blackwood
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Location: North East Victoria

Re: Nitrocellulose issue

Post by blackalex1952 » Sun Dec 06, 2020 10:12 am

Thanks for the replies gents! I suspected that there would be a chemical solution to this problem, the article re the thinners was great. However, elbow grease seems to be the best option here. Does anybody have any theories as to why this occurred in the first place? The Claro Walnut was dried to 40% RH during the entire process from body assembly to sprayed finish, including some time afterwards in the dehumidifier prior to storage in the case inside my house at what I would estimate averaged 60% RH. The Walnut had been in dehumidified storage for a number of years prior to using it, and I've I've never seen nitro craze so rapidly, having used it for other builds that have not had a problem....same batch of wood. Maybe the crazing was caused by how I mixed the different coats of lacquer as I applied them? It's a mystery! Cheers! Ross
"Everything I say on the topic is based solely upon inexperience and assumption!"

simso
Blackwood
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Location: Perth WA

Re: Nitrocellulose issue

Post by simso » Sun Dec 06, 2020 4:16 pm

I have seen many guitars and headstocks that have been repaired with cellusolve or equivelant and sorry not impressed at all, there are always witness marks, bubbles, crazing left on the surface, to franks website and photo, a photo simply shows a smooth reflective finish it does not in relality show you what the surface looks like.

Sometimes crazing just happens, i suspect its been exposed to an extreme cold situation, if i want a vintage nitro look, i can paint it today put it in the freezer tonight and when i take it out tomorrow the finish is cracked everywhere.

Steve
Steve
Master of nothing,

Do your own repairs - http://www.mirwa.com.au/How_to_Series.html

blackalex1952
Blackwood
Posts: 777
Joined: Tue Aug 27, 2013 6:36 pm
Location: North East Victoria

Re: Nitrocellulose issue

Post by blackalex1952 » Sun Dec 06, 2020 6:36 pm

Steve, it certainly gets cold in the mountains here in winter, for Australia that is. Regular -3 to -5 degrees! With permafrost in the soil....it gets into ones bones! P
robably the reason the finish crazed...pity the guy didn't want a retro "reliced" look! I would have been fine with that...can of elbow grease on the shopping list this end! -Ross
"Everything I say on the topic is based solely upon inexperience and assumption!"

simso
Blackwood
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Joined: Mon Apr 25, 2011 10:36 pm
Location: Perth WA

Re: Nitrocellulose issue

Post by simso » Sun Dec 06, 2020 9:54 pm

Put a face mask on, well ventilated area and just keep wiping it down with a fresh rag and paint thinners, it will eventutally just wipe away back to the sealer coat

Many a time I have sat there and removed a nitro finish with thinners and a face mask

Steve
Steve
Master of nothing,

Do your own repairs - http://www.mirwa.com.au/How_to_Series.html

blackalex1952
Blackwood
Posts: 777
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Location: North East Victoria

Re: Nitrocellulose issue

Post by blackalex1952 » Mon Dec 07, 2020 3:42 pm

Thanks Steve, so glad that you chimed in here. We all owe you a debt of gratitude for your 'how to' series, which was also a very professional effort and quite unconditional. Hats off to you for your achievements in running you business as well. Thank you. Kind regards Ross.
"Everything I say on the topic is based solely upon inexperience and assumption!"

blackalex1952
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Posts: 777
Joined: Tue Aug 27, 2013 6:36 pm
Location: North East Victoria

Re: Nitrocellulose issue

Post by blackalex1952 » Mon Jan 04, 2021 2:29 pm

The job has nearly been done on this repair...I found that using a scraper was faster then followed by the thinners to strip...that way less fumes and health issues along with saving a LOT of expensive thinners....nitro thinners are extremely volatile as well...cheers! Ross
"Everything I say on the topic is based solely upon inexperience and assumption!"

simso
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Re: Nitrocellulose issue

Post by simso » Mon Jan 04, 2021 11:27 pm

I just use gun wash thinners, save the expensive stuff for painting :D
Steve
Master of nothing,

Do your own repairs - http://www.mirwa.com.au/How_to_Series.html

blackalex1952
Blackwood
Posts: 777
Joined: Tue Aug 27, 2013 6:36 pm
Location: North East Victoria

Re: Nitrocellulose issue

Post by blackalex1952 » Tue Jan 05, 2021 12:18 am

I have been wondering if gunwash thinners would affect the respray down the line....a hand build that I don't want to compromise, but if you have experienced a stable end result let me know....a much cheaper option but still lots of fumes, so I'll go with a scraper first then the thinners then sanding before respray...lots of work I didn't expect to have to do on this one that for sure. Cheers! Ross
"Everything I say on the topic is based solely upon inexperience and assumption!"

blackalex1952
Blackwood
Posts: 777
Joined: Tue Aug 27, 2013 6:36 pm
Location: North East Victoria

Re: Nitrocellulose issue

Post by blackalex1952 » Sun Jan 10, 2021 12:49 pm

What worked for me most efficiently. A light wipe with gunwash to soften the nitro then a Caruthers scraper followed by a sanding. Cheers! Ross
"Everything I say on the topic is based solely upon inexperience and assumption!"

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