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Hi all.

A customer sent me pictures of his Contreras M-2 Study guitar with two white spots on the back. Would anyone know what causes those and if it can be repaired?

For now I'm guessing water/humidity damage on a waterborn finish, but I'd like to know what you guys think.

Thanks!

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Alain Moisan
Former full time builder of Acoustics, Classicals and Flamencos.
(Now building just for fun!)

It is hard to tell for sure as the resolution of the photo is not clear enough to tell but appears to be a chemical contamination spot, inclusion or blush in the finish. The fact that it is 3 distinctive round spots makes me believe that something has splattered onto the finish causing it to blush or haze over. The fact that the three spots seem to be geometricly placed is courious, almost forms a right triangle like a small 30 degree drafting angle.

Thnaks for your answer Micheal.

It's actually only two spots, the third blurry one is probably something else since the customer only mentioned two spots. The guitar was made in 1999 and the spots only appeard recently. Could that still be caused by chemical contamination of the finish?

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Alain Moisan
Former full time builder of Acoustics, Classicals and Flamencos.
(Now building just for fun!)

Well if the guitar is 10 years old and the spots are recent then something has been splattered on the finish that has caused the finish to blush or haze or worse degrade. That is an easy enough deduction.

Most likely alcohol or an other solvent or acid base.

If that would be the case, then do you think it's only on the surface? Meaning a little sanding and polishing might fix it?

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Alain Moisan
Former full time builder of Acoustics, Classicals and Flamencos.
(Now building just for fun!)

Unless it is a solvent that was able to penitrate the finish, but would expect to see some creatoring or blisering as well

Alain ;
I just had a factory Sp. guitar in here with the same problem!
Nothing was spilled on it and it also just appeared !!
I think Mike P. is on the money -there must be a contamination of the finish that takes years to show up!
Those finishes are very thick so this is possible!

The guitars in question are not worth a big repair bill !

The haze is trapped inside the finish-sanding may release it-let us know please!!

Mike

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Mike Collins

Thanks a lot for your responses guys. I appreciate it.

I told my customer it was worth bringing the guitar to me to see it up close, so I'll let you know how it goes. If you don't hear about me, it'll be because he never came back to me...

Thanks again!

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Alain Moisan
Former full time builder of Acoustics, Classicals and Flamencos.
(Now building just for fun!)

Any chance that could be from a belt buckle or something like that. They look rather uniform in shape and size. Maybe pressure in the same location over the years has caused this. I have some similar looking marks on the back of my Takmine and I'm sure it's only from years of pressure from a belt buckle or the rivits which are on most jeans.

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They are very much on a plane that is near perfectly parallel to the center seam. You would not expect that if it was splatter or pre or post finish contamination