Finish (shellac?) repair suggestions on Spanish classical

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demonx
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Finish (shellac?) repair suggestions on Spanish classical

Post by demonx » Thu Aug 08, 2019 11:35 am

I’m comfortable with modern finishing however I’ve never working with older style finishes, so I’m writing in hope some of the traditional method guys here may have some insite.

I have a classical on my bench for a service and clean up and I’m guessing it has a shellac or some other traditional style finish, although I wouldn’t bet any money on that. The guitar is a Antonio Ruben, made in Spain.

Heat has been applied when the bridge was removed at one stage and the finish has been burned resulting in what looks like a separation of compounds in the finish, (as can be seen in the photo).

I also cleaned up a lot of superglue where the DIYer repaired his own top crack, but I’d like to get this burn area looking much more pleasant.

I’ve never worked with shellac finishes (or whatever this is) in my life, are there any suggestions on how I can make this less obvious or hidden all together?

I’m guessing a full refinish however I thought I’d throw it out to the experts here for an opinion.
93958E4B-62B5-4B9F-84E1-8F3AD2AF5173.jpeg

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demonx
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Re: Finish (shellac?) repair suggestions on Spanish classical

Post by demonx » Thu Aug 08, 2019 11:37 am

D8E9D8D6-F290-42EB-9E38-41D7F6EC63AF.jpeg

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Re: Finish (shellac?) repair suggestions on Spanish classical

Post by johnparchem » Thu Aug 08, 2019 12:48 pm

I have never seen that with shellac even from heat. It seems like on the way to refinishing you can try and sand it out. I have used behlem qualasole for repairs on top as it sticks to nearly anything and can be padded on. I have done whole tops with it and it builds quickly and looks great. I think it is a combination of shellac and nitrocellulose.

https://www.shellac.net/Qualasole_label_text.html

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Re: Finish (shellac?) repair suggestions on Spanish classical

Post by demonx » Thu Aug 08, 2019 12:53 pm

I gave it a light cut at there was superglue everywhere and now I can see this area clearly it looks 3D, as in, to get rid of the “flakes” the finish would have to be sanded to wood, not just the surface.

That’s why I guessed it’s a shellac finish, it looks like the flakes have uncured and become visible? I’m not sure how to explain

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Re: Finish (shellac?) repair suggestions on Spanish classical

Post by Trevor Gore » Thu Aug 08, 2019 1:44 pm

Looks very weird!

Has a soldering iron been used to try to steam out dings?

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Re: Finish (shellac?) repair suggestions on Spanish classical

Post by demonx » Thu Aug 08, 2019 2:18 pm

Trevor Gore wrote:
Thu Aug 08, 2019 1:44 pm
Looks very weird!

Has a soldering iron been used to try to steam out dings?
Not at all, it’s simply a finish reaction to direct heat making the compounds in the finish separate.

To the eye it looks like flakes floating in clear coat.

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Re: Finish (shellac?) repair suggestions on Spanish classical

Post by kiwigeo » Thu Aug 08, 2019 9:36 pm

I recently had a friend with a church pew that had had a hot plate put on the french polished finish. I went over it with a munec lightly loadd with meths it came good. The cloudy patch in the background top in your photos is classic FP after its had something hot in contact with it.The patch you're talking about looks like its had some serious heat applied to it.
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Re: Finish (shellac?) repair suggestions on Spanish classical

Post by peter.coombe » Fri Aug 09, 2019 10:07 am

Weird, never seen anything like that before. Maybe it has been spattered with very hot water. The cloudy patch does look like heat damage to shellac.
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Re: Finish (shellac?) repair suggestions on Spanish classical

Post by Trevor Gore » Fri Aug 09, 2019 10:44 am

The darker patches look like a water stain - the sort you get under varnish when wood has been left in damp conditions for a long while. So that makes me wonder if some sort of re-hydration was attempted with water spilling inside the guitar. I don't know of any finish that fails with white dots like that though (unless spot heated).

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