Acoustic Guitar Construction

I was just wondering if you can use Zpoxy to fill a
hairline crack and will this also hide it?

What kind of wood?

ken cierp wrote:What kind of wood?

Mahogany, Goncalo Alves, Indian rosewood....Can it be
used on any of these?

CA is a better choice -- especially if repairing structure. But -- your key word is "hide" you need to experiment and see what really hides or "tricks the eye" If its just filler on dark wood and the crack looks like grain something clear might work. Otherwise you need to color match. Shellac sticks work good for that purpose. On Rosewood a little RW dust and CA will become invisible.

I don't have a picture, but perhaps a 1000 words is worth a picture...?????
Oh well, anyway.
I had an experience using CA to fix a crack in the last guitar I finished, which was Santos Mahogany. It is a medium dark colored wood, not as dark as EIR but darker than Honduras Mahogany. This crack was in one of the back panels, up about 5 inches into the lower bout area. It was tight and didn't really need clamping, but I flowed CA into the crack and pulled the crack tight with tape across the crack. It held all through the building process but did show up as a slight black line, but not unlike the surrounding grain. I KNOW that it was filled, flat and secure.
However, when I applied the finish (Nitro) and got to the polishing stage, the crack showed up as what I'm pretty sure is like "refracted light" coming off the CA in the joint. My finish is flat, but at an angle, you see this line. Nothing I could do about it, but it made me think, that on any wood other than very dark grained, I will be using my LMI glue for this type of repair in the future.

Kevin

Why would the LMII PVA glue work better and be more invisible? Perhaps if you scuffed up some dust and packed it into the cracked area (my recommendation, of course not on spruce) before applying the CA to the tiny fracture? Also, most filling is best done after the seal coat is applied to prevent the glue from becoming a localized sealer --- that can be real mess that shows up after a few coats of finish has been applied. I have never worked with Santo Mahogany so I surely don't know what would work best. So I guess the lesson for all of us is to practice our repair procedure on some scrap -- these appearance repairs are about tricking the eye -- not always easy to do. Kevin I bet this flaw is something only you could find.

It is a strange one to be sure, even hard to explain....as you can see.
I don't think the man who has the guitar notices it. So it is all good!
The glue PVA glue is a guess, no science there.

Kevin