Repair suggestions

Construction and repair of Classical Guitar and related instruments
ghenson
Posts: 168
Joined: Wed Oct 31, 2007 3:45 pm

Repair suggestions

Post by ghenson » Wed Mar 13, 2019 10:22 pm

Just about finished with this repair. I glued it back together with polyurethane glue, added carbon fiber pins,replaced the face veneers, and put down a French polish.

I need some suggestions on the following:
Matching the color
Better disguising the fracture line on the back side
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ghenson
Posts: 168
Joined: Wed Oct 31, 2007 3:45 pm

Re: Repair suggestions

Post by ghenson » Wed Mar 13, 2019 10:23 pm

Mostly complete
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Marshall Dixon
Posts: 771
Joined: Fri May 15, 2015 5:06 pm
Location: SW Oregon

Re: Repair suggestions

Post by Marshall Dixon » Thu Mar 14, 2019 3:33 pm

ghenson wrote:
Wed Mar 13, 2019 10:22 pm
Just about finished with this repair. I glued it back together with polyurethane glue, added carbon fiber pins,replaced the face veneers, and put down a French polish.

I need some suggestions on the following:
Matching the color
Better disguising the fracture line on the back side
Nice job on that repair.

The first thing I try when coloring mahogany (it appears to be that) is potassium dichromate.

I've used tincture of iodine to darken the glue line (if that's what you're trying to do) with Titebond type glues but never tried it on polyurethane glue.

ghenson
Posts: 168
Joined: Wed Oct 31, 2007 3:45 pm

Re: Repair suggestions

Post by ghenson » Thu Mar 14, 2019 11:16 pm

I will check in to that. Have not heard of it.
I have some garnet shellac that I’m hoping will darken the light areas

khs
Posts: 66
Joined: Tue Jan 22, 2019 7:20 am
Location: SEOUL, KOREA

Re: Repair suggestions

Post by khs » Fri Mar 15, 2019 1:34 am

If I were in such a situation I would :
1. Remove the cracked portion of the back side shellac finish
2. Apply CA-glue along the cracked line
3. Wait 1-2 minutes
4. sand over the lesion till it flattened
5. finish with shellac over the site as usual

Marshall Dixon
Posts: 771
Joined: Fri May 15, 2015 5:06 pm
Location: SW Oregon

Re: Repair suggestions

Post by Marshall Dixon » Fri Mar 15, 2019 3:50 pm

ghenson wrote:
Thu Mar 14, 2019 11:16 pm
I will check in to that. Have not heard of it.
I have some garnet shellac that I’m hoping will darken the light areas
Potassium dichromate, or bichromate (yes, it's toxic) darkens and gives mahogany a lovely red/brown hue. I make a 10% solution. Purchased from Woodfinishing Enterprises.

The glue line is another matter. Iodine dyes carbohydrates blue/black. For your purpose it may be too dark and stand out more.

And the polyurethane glue probably won't do the same thing as aliphitic resin glue. Maybe some colored felt tip marker. Or if there is an indentation it could be filled with something as @khs suggests. I've mixed fine sanding dust with slow acting CA glue as a fill with good results.

Just a thought, but you might call Woodfinishing Enterprises and ask about dying polyureathane glue.

ghenson
Posts: 168
Joined: Wed Oct 31, 2007 3:45 pm

Re: Repair suggestions

Post by ghenson » Fri Mar 15, 2019 6:27 pm

khs wrote:
Fri Mar 15, 2019 1:34 am
If I were in such a situation I would :
1. Remove the cracked portion of the back side shellac finish
2. Apply CA-glue along the cracked line
3. Wait 1-2 minutes
4. sand over the lesion till it flattened
5. finish with shellac over the site as usual
I have done this procedure already. I cannot feel the
line.

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