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Mar 6, 2021 - 9:13:57 PM
10 posts since 7/11/2018

I am fixing an old brittle top. Where it fastens to the block at the tailpiece end are crevices from deterioration. Is there a good wood putty?

Mar 7, 2021 - 4:13:14 AM
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183 posts since 11/28/2018

Assuming it's a spruce top I would make a slurry of spruce sawdust in hot hide glue. And if any of the crevices were large enough would use splinters of spruce also. Maybe some of the real luthiers will chime in here.

Edited by - Woodcutter on 03/07/2021 04:14:13

Mar 7, 2021 - 2:00:25 PM
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5536 posts since 7/1/2007

I and the guys I worked with usually soak the splinters off and glue them back where they came from with hot hide glue. The inevitable little gaps get filled with Elmer's wood filler (water based and reversible) Some of the guys mix it with hide glue. Splinters and slivers to fill cracks works OK. The sawdust and glue slurry looks pretty ugly to me in any finished area.

Mar 10, 2021 - 12:55:45 PM
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9038 posts since 3/19/2009

quote:
Originally posted by KCFiddles

I and the guys I worked with usually soak the splinters off and glue them back where they came from with hot hide glue. The inevitable little gaps get filled with Elmer's wood filler (water based and reversible) Some of the guys mix it with hide glue. Splinters and slivers to fill cracks works OK. The sawdust and glue slurry looks pretty ugly to me in any finished area.


A finer analysis has never been made!!!!laugh Sawdust and glue always looks like sawdust and glue, but a well fit splinter can look very natural, or at least like WOOD...!

Edited by - TuneWeaver on 03/10/2021 12:56:01

Apr 3, 2021 - 8:39:48 AM
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46davis

USA

6 posts since 3/16/2021

You can make a filler that has minimal impact on the sound by making a paste of sanding dust with a little acetone. Acetone partially dissolves cellulose and the past adheres to wood absolutely. When the acetone dries, which it does quickly, the paste has about the same density and strength as the wood it replaces. There is a commercial product that uses this combination, but I don't know what kind of wood the paste is made of. I used a spruce sanding dust.

I used this formula to repair a top and I'm very pleased with the result. I don't think it affected the tone at all; or if it did, I think it was less than a glued repair due to the greater density of the glue.

(Acetone doesn't seem to work gluing wood together.)

Apr 3, 2021 - 9:24:26 PM

368 posts since 3/1/2020

It’s better to keep fillers to a minimum on plates. There are some instances where they are more practical, but in most cases, replacing missing wood with wood yields much better results.

Glue and fillers are harder than the wood and don’t tend to respond to climatic conditions the same way the surrounding wood does. Over years of expansion and contraction, fillers can come loose and either chip away or cause buzzes. Also, it’s not a good idea to use things that can’t easily be reversed; someone else is going to have to work on the instrument in the future, and it really compounds the difficulty of the work when old repairs have been done without any forethought. When I do restoration work, I spend a great deal of my time getting rid of botched repairs.

One of the great characteristics of hide glue is that it can form a strong bond between two like pieces of wood without much film thickness. Some amateur workmen will attempt to use thick glue as a gap filler for poor joints, but that has disastrous consequences.

Apr 14, 2021 - 5:28:31 AM
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807 posts since 1/9/2009

I have been surprised at the good visual results by using well-matched spruce pieces to fill the missing wood in the top. Glue in place with aliphatic resin glue; carefully level with small scraper without damaging surrounding area; drop in clear CA (allow to dry naturally - no accelerator) and relevel; repeat CA and leveling as needed to level the surface; finish with topcoat of choice followed by micromesh as needed (grits 600-12000). Use progressively finer micromesh to match the sheen of the surrounding areas. Sometimes you have to stop at 3000 to prevent an overly reflective surface, which looks newer than the surrounding area.

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