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This is the Bruno guitar that when I bought it had the back held on with duct tape.  When I went to match the back up with the sides, there was a marked concavity to the outside of the back.  The edges of the lower bout were 5/8 inch higher than the center line.  After removing the mahogany back braces, the BRW back flattened right out.  Again, it seems as though the rosewood shrank more than the mahogany.  The last picture shows the flattened back.

Now, the question.  The inside of the back is covered with multiple slash marks, some of them quite deep.  I thought that this was somebody's idea of providing "tooth" for gluing.  Under the braces, though, there is evidence of the finer, more usual tooth marks.  What then was the purpose of the slashes?  Has anybody else seen this?

Thanks once again for your insight and expertise.

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The slashes and tooth marks.

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Hi, My first thought was that the board may have been used for another purpose prior to becoming a guitar back. Those score marks look like the top of my bench in places where I have been scoring template or veneer with a knife. Removing them may have made the plate too thin.

The deeper groove may have been made by the edge of a plane whilst shaping the braces.

Or......maybe not.

Cheers Taff

 

Well, this is an interesting piece!  I've got three Bruno's in the pile, none of which show the concave back this one has.  I have to agree that the braces and the back must have shrunk at different rates. I assume you'll just clean and re-use the original braces now that the back has resumed it's normal shape (did the braces go back to flat as well?).

Re the back, the fine tooth marks are reminiscent of others I've seen that were clearly creating a tooth for glue.  The slashes, though, I've never seen before. Quite crude. It's almost as if someone was scoring the wood before planing by hand to thin it out, perhaps to remove thickness faster.  

Hey Taff and Chris, thanks for your interest and comments. 

There isn't a center graft in the middle of the back, nor a center inlay on the outside of the back.  The slashes go all the way across the back, so they were done after the back was joined.   There are no slash marks under the braces, so it looks as though the slashes were done after the braces were in place. 

There are smaller, shorter slashes around the edge of the back that go right to the edge, suggesting that they were made before the back was glued on, or maybe some time when it was off.

The finer tooth marks are very regular, 40 per inch, and just like those you see on the bottom of many old bridges.

The slashes are still a mystery to me.

George

Chris, when reading back through your post , I realized that I hadn't answered your question about the braces.  They all maintained the same curve when off the back.  The narrower ones across the upper bout came off intact, but the flatter ones were badly splintered (perhaps saying something about the effectiveness of the toothing).  I have a lot of spruce bracing on hand, but nothing in mahogany.  As much as I like to keep things as original as possible, I'll probably go with the spruce.

The mahogany braces were very light weight and quite soft.  The mahogany that I have available is very heavy and hard.

George, excellent observation!  As a former archaeologist, I should have noticed that. Boy, I'm with you... just can't imagine what the cuts were for.  I went back and found a shot of one a

Bruno I worked on a couple years ago.  Similar bracing (and mahogany as well) but definitely NOT concave, actually it was  slightly convex.  And no cuts.

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