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Top Damage Advice Needed

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Top Damage Advice Needed

Postby Eric Knapp » Wed May 31, 2017 4:35 pm

Hello,

Something fell on the guitar top I'm working on and damaged it. You can see damage here:

damage - 1.jpg
Damage

There's a dent, a scratch, and a crack. Before I flail away and try to fix it I am looking for some input from all you folks. Since this is my first build I'm upset. I suspect this is not uncommon and I'm more upset than I should be. Is this salvageable? What should I do? The crack does not go beyond what you see, there's a brace holding it. The dent seems pretty deep to me but the fibers don't appear to be cut or torn. The scratch is a cut but I might have enough extra thickness.

This is a learning build so I will certainly glue the crack and keep building it. I'm wondering what you pros and experienced folks would do.

What's the prognosis?

Thanks,

-Eric
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Re: Top Damage Advice Needed

Postby Bob Orr » Wed May 31, 2017 4:59 pm

I think the crack will re glue ok. The dent can be improved with a wet cloth and some heat. Put a damp clean cloth over the dent and apply heat on top of the cloth with the tip of an household clothes iron or a soldering iron. Repeat as necessary. This has worked for me so long as the fibers are not broken and in best case is not visible at all. You may want to wait until some more experienced guys chip in but this has worked for me. Bob
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Re: Top Damage Advice Needed

Postby Peter Wilcox » Wed May 31, 2017 5:01 pm

Steam iron the dent and the scratch, then glue the crack. (Edit - as Bob says above.)
Maybe I can't fix it, but I can fix it so no one can fix it
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Re: Top Damage Advice Needed

Postby Bob Gramann » Wed May 31, 2017 5:42 pm

What they said plus move your worktable to the center of the room away from the walls so that nothing hanging on the wall can fall on it. Don't sand your top too thin trying to make the scratch disappear. First use the wet cloth and the hot iron on that, too. You want to thickness the top for optimum acoustic properties not for appearance. If the scratch is too deep, you can use hide glue to glue a splinter of the same wood into it to fill it. That repair sanded flush might even make it disappear.
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Re: Top Damage Advice Needed

Postby Eric Knapp » Wed May 31, 2017 7:45 pm

Thanks, guys. I will try the iron and cloth way first. I should probably do that before I glue the crack. The top was not on my workbench, I was working on other things. I don't have a safe place to store works in progress and I realize I need one. I'm looking at ways to add something to my shop for that.

I also won't try to sand the scratches and dent out, that wood is too thin and fragile. I'll make it as is, there's a lot to learn.

-Eric
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Re: Top Damage Advice Needed

Postby Beate Ritzert » Thu Jun 01, 2017 6:05 am

Eric Knapp wrote:I also won't try to sand the scratches and dent out, that wood is too thin and fragile.


You might use the dust from sanding a rest of the same wood and hide glue to fill the scratches. That only adds material to the top, and does not take away anything.
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Re: Top Damage Advice Needed

Postby Barry Daniels » Thu Jun 01, 2017 11:44 am

I beg to differ. I think sawdust and glue makes an ugly filler especially on light colored wood.
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Re: Top Damage Advice Needed

Postby Mario Proulx » Thu Jun 01, 2017 1:21 pm

No sawdust and glue! That just highlights everything....

You have an excellent opportunity to learn to steam out dents. It's not hard, you can't do it 'wrong' on a raw top like this(as opposed to a completed instrument) and you'll learn an invaluable skill.

It will come out perfectly.
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Re: Top Damage Advice Needed

Postby Alan Carruth » Thu Jun 01, 2017 1:28 pm

Sawdust and glue is a lousy filler. Violin makers use lycopodium powder. These are spores in the form of a fine air-dispersible off-white powder that mix up to very nearly the color of spruce or maple in hide glue. It's a pharmaceutical, and you may be able to get it through a sympathetic druggist. Kremer pigments in NY also sells it. I found out about Kremer just after 9/11. I wanted to order some, but it seemed like a bad time to be ordering a biologically active air dispersible off-white powder through the mail. I mentioned my dilemma to my students and one obtained about a kilo through his druggist. A kilo of this stuff is a couple of big jugs full. All of the students ended up with as much as they wanted, and I still have a couple of lifetimes' worth.

The quicker you get at a dent like that the better the results are likely to be. Sometimes if you hit it right away you can swell it out with just a drop of water. I like to allow the water to soak in until it starts to dry by itself, and then wet it again, and warm up the spot with a hair dryer or heat gun. When it's dry I put on another drop or so while the wood is still hot, and warm it up again. This will get most dents, unless the fibers are actually broken. In that case you're sort of stuck in any event.
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Re: Top Damage Advice Needed

Postby Beate Ritzert » Thu Jun 01, 2017 5:48 pm

Maybe it is just a problem of me not being a native english speaker. To me a scratch is something elongated cut into the wood. I.e. broken fibers. Thats why i suggested filling the scratches appropriately.

The dent is a fully different story - i never think of filling it before trying to steam it. I actually use an injection needle to produce drops of matching size.
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Re: Top Damage Advice Needed

Postby Clay Schaeffer » Sun Jun 04, 2017 9:22 pm

"You might use the dust from sanding a rest of the same wood and hide glue to fill the scratches"
That is pretty good advice when using high clarity hide glue, and I have also had good luck getting a good color match using sanding dust and the finish material you will be finishing with as a binder instead of glue.
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Re: Top Damage Advice Needed

Postby Alan Carruth » Mon Jun 05, 2017 5:07 pm

Sanding dust and glue always ends up darker than the wood. That's why he fiddle folks use lycopodium. I think I tried just about everything over the years, and that's the only one that works, more or less.
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