French polish turning green/gray

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BionBit

Posts: 2
Joined: Jun. 21 2020

French polish turning green/gray

Hello all,

Today I've noticed an area on the side the guitar that has a green/gray tint, which wasn't there before. Does this normally happen with french polish? Oxidation maybe?
The guitar is stored in a solid case when not played, room temperature and humidity should be in the normal range.

I'm playing a concert Francisco Navarro made this year (beautiful guitar by the way).

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REPORT THIS POST AS INAPPROPRIATE | Date Oct. 14 2020 20:16:36

constructordeguitarras

Posts: 1674
Joined: Jan. 29 2012
From: Seattle, Washington, USA

RE: French polish turning green/gray (in reply to BionBit)

I suspect that it is wax blooming out of the finish. Sometimes that happens if the shellac was not sufficiently dewaxed. Though I've only experienced it happening on bindings for some reason.

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REPORT THIS POST AS INAPPROPRIATE | Date Oct. 15 2020 5:43:22

RobF

Posts: 1611
Joined: Aug. 24 2017

RE: French polish turning green/gray (in reply to BionBit)

Do you sometimes rest your chin on the bout when playing? I’ve seen a yellow/green discolouration in the shellac on the lower bout of a guitar which was due to sweat accumulation that was not being cleaned off the guitar. The stain looked similar to how a white shirt can sometimes get stained around the armpits. I read that the sweat itself doesn’t cause the discolouration, as it’s colourless, instead it’s from the discharge of bacteria that feeds off the sweat (something to think about if you’re resting your chin on the guitar, lol).

REPORT THIS POST AS INAPPROPRIATE | Date Oct. 15 2020 8:38:27

BionBit

Posts: 2
Joined: Jun. 21 2020

RE: French polish turning green/gray (in reply to BionBit)

Thanks Ethan, Rob.

Yes, that's a good point, I do rest my chin in that area. While I use a cloth for cleaning the guitar once in a while, I didn't expect the shellac to be affected. Did thought about breathing there which might be related.
My other guitar (classical built) has a Polyurethane finish, which is stronger and never had this issue.

I like the shellac more but damn it's sensitive!
As long as it's just coloring and doesn't affect the wood, it doesn't bother.

Cheers!

REPORT THIS POST AS INAPPROPRIATE | Date Oct. 15 2020 9:25:25