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I always end up with a few (or more) tiny gaps in the rosette rings and the binding, especially wood binding, that require filling.

I do the fills after a couple of coats of NC lacquer. For fills I've used 1) GluBoost Thin CA, 2) 12 hour epoxy, 3) lacquer straight from can drops fills and 4) thickened lacquer. I have experience the following using these methods:

Lacquer takes a long time to dry and shrinks back for weeks.

CA dries hard and brittle and sometimes has tiniest of bubbles (GB accelerator at 12" away) sometimes requiring a follow up drop of lacquer.

Epoxy is easier to scrape with the taped razor blade but hard to get a thin drop.

What is your method to do "drop" fills?

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Measure Twice,

Karl Borum

Well ca has worked well for me. Use the appropriate viscosity so it doesn't disappear into the interior of the guitar. It does sink so several applications are needed. Don't use accelerator on it since it tends to foam. Be patient! On my early efforts there was quite a lot of time spent on bindings that didn't fit very well! Be prepared to let it settle for some hours - overnight- perhaps before taking the tiny nozzle over it again. The excess does scrape off easily enough. Keep going, using slanting light and a magnifier until you are sure you are above the surface of the surrounding timber.

On rosettes I would worry about it staining the spruce top wood so have tended to go to epoxy but it is hard to cut back. If the gaps are small drop filling with your finish is probably safer.

This problem does get easier as you find a technique to get things to fit bettter.

Cheers Dave

I have to be careful about gaps because I’m spraying UV poly which will build up on the tiniest little edge. I have been using whatever the porefill is to fill in any gaps. I use wood rosette rings so that has to be pore filled as well anyways.same for the edge grain of wood binding on the sound board side of the body.


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If you’re bordering rosewood, you’re home free. Shellac everything first to protect the woods, especially spruce, from the CA. Pack the gap with rosewood dust and drop ultra thin CA into it. After scraping level and sanding, the gap is likely gone. Ebony works the same way.

Where there is black-bordered purfling, I judge whether having the black a little wider will look weird. If not, again after shellac sealer, I use black CA.

For bindings of lighter wood, I make a paste of that wood’s dust. Sanding scraps to make the dust, I mix a PVA (I like the Lee Valley tan woodworker’s glue because it’s not yellow) with a drop of a surfactant (like Rinse-Aid) with a pile of dust and work it into the gap (again after shellac). The surfactant allows the glue to mix in with the dust a bit more easily without repelling it. Wiping the area adjacent with a damp paper towel to remove the excess glue makes the cleanup after the patch dries a lot easier. This works a lot better with darker woods and sycamore than with maple, but sometimes even a gap against maple totally disappears.

Sometimes, I will purfle the line between the binding and the body after I glue on the binding. I think it was Michael Greven who showed how to do this in a GAL article a long time ago. The miniature circular saw Dremel bit cuts a slot sized just right for a .040” purfling line. Cutting this after installing the binding absorbs any gaps into the purfling slot.

Break off a little piece of shellac flake and place it over the gap, and press it in with a hot thing. Shellac melts at 167F.

Have you tried Shellac or lacquer burn in sticks? They work great

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I forgot to mention that I first put a drop of water into a binding gap and heat and press the binding in to close the gap (I do my bindings with HHG). I only fill when the gap is small and the binding solid and immovable.

I will have to play David’s and Dennis’s shellac and burn-in sticks. That sounds like a great method.

Karl I always used Titebond original for rosettes and I would cut out the rosette and then mill the channel until I had a slight press fit. When I applied the Titebond I worked fast and I used a bit more glue than usual so that it would slightly swell the channel shut. And it did. Worked great, no gaps.

many ways to do this. I don't use CA on spruce as it will stain over time. I do a lot of finsh work and my go to is
thickened lacquer. I look for the gaps after the first 2 coats and start the body and fender work. I use duco exclusively on rosettes. I always had issues with tite bond grabbing too fast.
Duco is also finish friendly and without water it won't swell and pinch things off

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John Hall
blues creek guitars
Authorized CF Martin Repair
Co President of ASIA
You Don't know what you don't know until you know it

Dennis, David Foster and Bob,
Funny you should ask about shellac stick.
Yes, I gave that a test-whirl yesterday on a lacquered board I keep around, and it worked fantasticly, as a test.

I used an alcohol lamp and a fine artists pallet knife with some transparent lacquer stick. The test repair worked very very well but…. that lacquer really needs a lot of constant heat to melt it and a pallet knife did not have enough mass to stay hot enough. I had to heat the entire pallet surface to hold enough heat to even get a drop of lacquer stick. I actually ordered a 110V lacquer knife from Shellac.net yesterday along with a set of sticks. I can also use them on my wood floors…… I will not use that method until I get the hot knife (which can be controlled with a router speed cpntrol to control the heat).

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Measure Twice,

Karl Borum

Skip to the end if you dont like to read a long post....*

Coming clean about the question..... I had a lacquered body fall off the bench after a wet sanding session.
It cracked the top and shattered the lacquer at the impact point.
I scrapped all the lacquer off the top with a thin scraper.

While doing that, some of the grain from the fiddleback maple binding tore out. About a 4" section of that binding has a serrated edge like a steak knife where the grain tore out from the scraper. Its very small but noticeable, and you can feel it so its got to be fixed (splicing in a new piece is out of the question for good reasons). Small prior drop fills came out with it.

The tear out is shaped like a cone that starts on the top of the binding (like coplanar with the spruce top) and ends on the side of the binding. I think the area is too large for a lacquer drop, which I attempted. GluBoost drop resulted in sand through getting it level. Its a repair from hell and I've been working on it, slowly, since JULY.

Good news is that I am 99% there, the final touch yesterday and today was applying CA from a puddle on a plastic lid with a .011 e string; FAR BETTER THAN EVEN THE FINEST OF WHIP TIPS.

I've been very calm patient and methodical about it rather than getting all red-hassed about it, it seems to part of finishing guitars.

*I did want to know what you guys favor for gap filing, and I have learned a lot from your replies, thank you.

_________________
Measure Twice,

Karl Borum

Pics please Karl? Thanks

Only finished sanded to 1200, never buffed.
These are the clearest pics I could get.
First is pic of repaired binding (needs sand throughs lacquered)
Second pic is of no-damaged binding.
Three coats of lacquer over the sand through tomorrow, then onward…

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Measure Twice,

Karl Borum

Here is a pic of the shellac stick repair test. I cut a piece of wood out with a 1/8 wide chisel, you can just see the rectangle. Added grain with the Pigma Micron 003 (thank you @Jeff Jewitt). Need a good heavy (thermal mass) tip to do this right.

EDIT: Just went back and looked at this pic, you cnat even see that repair, and I cut out a chunk! THis goes into the bag of tricks, I love this method. I delivered furniture for a small family owned furniture store, for a year, when I was young. Every piece that went out needed repair, this is how they did it.... except they had a small electric oven heater.

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Measure Twice,

Karl Borum

Nice repair on that!


Steve

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Steve Smith
"Music is what feelings sound like"

Thank you, Steve, they are always nice on a test panel.

The serrated edge is done now and turned out pretty good. I think I got the feel for the GLuBoost with this repair. I had a great phone call with Rick Rosenberg of GluBoost today. He said "accelerator on the surface before the drop and another shot after the drop". That allows the CA to dry from both top and bottom, toward the middle. HE said ALWAYS use accelerator. I'm now a fan.

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Measure Twice,

Karl Borum

Yes, I use the GluBoost products all the time. Anymore most gaps I get are pretty small and the GluBoost makes quick work of them.


Steve

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Steve Smith
"Music is what feelings sound like"