What to use for filling small cracks in guitar body

Gary_tele18

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Hi all,

I recently made my first "from scratch" body using alder from a local hardwood store. After milling to thickness there's a few small cracks on the surface of the wood. I was looking at a burst strat I have, and it looks like it may have had a similar issue, and the cracks were filled with "something". Wondering if any have recommendations on what to use to fill. In other (non-guitar) projects I've done, I haven't had great luck with standard wood fill, as it tends to swell a bit over time.

Thanks in advance.

Gary
 

Ryden

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On gunstocks I wet sand the stock with True-oil or slacum making a slurry that fills the pores.
When dry, the excess is sanded away (use really fine paper)
You could try the same using the finish of your choice.

This is all but invisible
 

Wheelhouse

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Try 30 minute Zpoxy and let it rest. Rest would be a good thing in any case as these cracks are generally from drying out as may have been green. Hard news to hear but wait at least a couple months then do the Zpoxy and wait another month. If no more new cracks, have at it 😉
I read this when you first posted it. Then wanted to find it again, thinking the comment had been about cracks in MY project. It seemed appropriate for me, too, since my slab was not sitting long enough to dry by conventional wisdom. This is the post I was looking for. ;)

I'm off to order the Z-poxy. I found the Stew-Mac video very helpful.
 

DrASATele

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Doing small batches of the 5 minute big box store stuff works too. I use it all the time and have had no issues when building guitars and using it. I tend to use it most when working with reclaimed lumber that has bug holes and tracks. Even though it says 5 minutes to harden, it take about 24 hours to get a full cure so it's solid and sandable. No matter what you use make sure it's completely cured otherwise when you sand it acts more like soft putty than sandable plastic.
 

schmee

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If fine cracks I'd use CA glue as it penetrates deeply.
Epoxy doesn't penetrate well at all.
If you use epoxy , try to not let it build much above the wood surface. Epoxy is pretty hard and it sands poorly. Often you can sand the surrounding wood when trying to flatten the epoxy.
 

Skydog1010

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A long long time ago I used DuPont's epoxy, I have forgotten the name of it, since it hasn't been available for more than 20 years, I don't know why I mention it other than I still have crates I coated it with, and they are still at work repelling all sorts of nasty chemicals and protecting the wood.

I then switched to PPG epoxy, there were two varients of it and it protected flexible stuff and the second version was for non flexible stuff. Came in three colors, white, grey and black. It was very expensive and was a three part or four part version depending on whether you needed the elasticity or not. There is outdoor furniture in use today I used it on about 20 years ago.

Now I use Zpoxy if I'm painting over top of it.

Otherwise, I French polish and that's about a 2000 word essay alone. Just say pumice, shellac and EverClear.

Guess I could have said (ZPOXY) that about 300 words earlier, maybe I wanted everyone to know just how old I am, and my lungs still work!

I'm lucky,!

Over and out.
 

nuclearfishin

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You didn't mention the finish you want, but if you plan on using stains or dyes, you'll want to stay away from epoxy until after the color is added. Prior to dyes I like using Timbermate. It doesn't shrink and it accepts dyes just like the wood. Many builders also use timbermate as a pore filler because it doesn't shrink and takes stain just like wood. Sawdust and CA is good for dark wood, but on a light colored wood like alder it will be darker in color than the surrounding wood.
 

OddSilas

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Thumbs up on the thoughtful suggestions. Both the super glue slurry and epoxy, depending on finish as already suggested. Just wanted to add definitely stay away from any softer “furniture “ finish fillers as they tend to deaden vibration. Also, I have some scars I’ve kind of grown fond of in a weird way, sometimes I lovem on guitars too!!
 

Havins

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if using an epoxy and you need to thin it you can mix in alchohol (over 90%)......I coated all my kitchen cabinets doing this for a thin seal coat prior to the thick pour coat in order to prevent late appearing bubbles....especially when filling knots
 

luthierwnc

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Alder tends to split internally if it's kiln-dried too fast (case hardening) -- especially with 8/4 stock. Alder is kind of a trash wood and mills don't always give it the care they do for their primary species. The faults are eye-shaped fissures that are biggest in the center of the board. I would make sure that what you see on the outside isn't wider a quarter inch down or it will never really stabilize. If the crack follows where you will be routing, punch a hole to look around.

If the cracks are more-or-less straight, you might cut really fine wedge-shaped strips and lightly tap them into place. Super-glue after or white glue before. Leave it proud for a day until the wood moisture equalizes before you plane/sand. sh
 

TheTealGuitar

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I almost ruined a tele build once (I got in too deep with the router on one spot) and I was thinking to fix it with some Bondo, but then I found the PC-Woody Wood Epoxy Paste and that worked for me like a charm. You do have to press it hard down into the gap though. It sands very well, but wait at least 24 hours before sanding. I'd say wait for 48hours for easy sanding.

Note of caution: although it does say on the product's label that it can be stained, it did not take the satin like the rest of the wood, so in the end I had to paint the guitar.
 

RRCaster

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Hi all,

I recently made my first "from scratch" body using alder from a local hardwood store. After milling to thickness there's a few small cracks on the surface of the wood. I was looking at a burst strat I have, and it looks like it may have had a similar issue, and the cracks were filled with "something". Wondering if any have recommendations on what to use to fill. In other (non-guitar) projects I've done, I haven't had great luck with standard wood fill, as it tends to swell a bit over time.

Thanks in advance.

Gary
Look into GluBoost products & videos:


I have done a number of repairs using it.
 

Freeman Keller

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Gary hasn't said how he is going to finish, what product(s), whether it will be opaque, tinted, clear. If it is opaque there are lots of materials, most have been mentioned before. Bondo works pretty good too. Gluboose is a great product for colored opaque or transparent finishes.

If he is going to put a clear or tinted finish on it the answer is much more difficult. If it is a small crack I would use one of the epoxies or finishing resin (Zpoxy), if its very small it can be drop filled with the finish itself (lacquer). The problem with mixing sawdust with epoxy or CA or wood glue is that it almost always looks darker than the parent wood. I use sawdust mixed with epoxy to fill small voids around inlays. That looks really good with dark woods but stands out badly with lighter woods. One thing that can work pretty well is to sand the surface while applying shellac, it will make a little slurry that fills cracks and provides a pretty good base coat for the top finishes.

Best answer is to eliminate the flaws before starting any finish. And as always, practice on scrap.
 




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