French polish turning green/gray (Full Version)

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BionBit -> French polish turning green/gray (Oct. 14 2020 20:16:36)

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).



constructordeguitarras -> RE: French polish turning green/gray (Oct. 15 2020 5:43:22)

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.



RobF -> RE: French polish turning green/gray (Oct. 15 2020 8:38:27)

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).



BionBit -> RE: French polish turning green/gray (Oct. 15 2020 9:25:25)

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!



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