I have searched and noticed previous discussion on glues, but there are a few things which I just need a little clarity on.

I'm recapping a bass bridge and repairing a few very minor cracks in the treble.

Regarding the recapping... I noticed Titebond has been discussed, and that Pianotek sells it...same stuff as in the hardware store, no less. Is this a hard-curing wood glue that would be good to use on the bridge cap? Also, I notice there is "Titebond II" and "Titebond III." If it's a good glue to use, would those be better still, or are they actually for different purposes and I'd be better off with the original. The labels were ambiguous about this.

For the cracks, I'm just curious about the best glue to use. I know CA glue is an accepted quick fix, but what I'm wondering is if it's better to use something else like slow-set epoxy when I have the strings off and the piano on its back already. There are some very thin CA glues which can work down very well, I know...but it doesn't strike me as the type of stuff that forgives if it fails (I think it's an inflexible bond, right?).

Greetings,
This is an acoustical joint, and all the energy has to go through it. For that reason, I would want the least amount of glue necessary, and I would use hot hide glue. If not that, I would use something that dries rock hard. I don't think titebond does, but resorcinol and several others do. Andre Bolduc has a white glue I would not hesitate to use for this. It dries very hard.
Filling cracks in what?

Thanks.

Cracks in the treble bridge...just a few small ones at the extreme high end. I was thinking epoxy might be better than CA due to flexibility, but I wasn't sure I could feel certain of it working into the particularly small cracks.

Titebond is somewhat harder than TB2 which has a claim to fame of being waterproof. Both will creep some. I would not be inclined to use either for a bridge cap but would choose the original over TB2 if I had no other alternatives. Don't know that much about the properties of TB3 though I'm sure the makers extol it's virtues readily on the internet.

What kind of glue/adhesive you use will also have to be weighted by what method you will use to clamp the joint. If the bridge is off the soundboard you could pick from many possible, normal, glues because you have access to both the top and bottom of the bridge root and will be able to apply fairly high clamping pressure.

Since a good glue joint using most glues requires a fairly high PSI clamp pressure, 80-100 lbs for hardwoods like maple, to give maximum strength, you must consider what glue/ adhesive in that light. If you cannot provide a consistent, high pressure clamping to the cap, then a epoxy matrix with colloidal silica would be a much better choice.

Colloidal silica will make the epoxy quite hard and will help bridge any gaps (pun intended) in the cap/root joint. Where a joint must be made under less than ideal clamping pressures for glue, the use of epoxy is a fine choice.

BTW, it should be noted that epoxy is NOT a glue per se. It is an adhesive and a gap-filling adhesive at that. The use of excessive clamping pressure would be counterproductive to a good joint.

Unfilled epoxy would be an excellent choice for filling small cracks in the cap. There are many viscosities available and a thinner viscosity would be appropriate for crack repairs.

West System epoxy has an excellent handbook on epoxy use that can be accessed on line.

Good info, thank you.

I do not have the bridge off the soundboard. I wasn't overly optimistic about getting it off without damaging the soundboard. I have carefully shimmed between the relevant ribs and the posts on the back of the piano, so with go bars, I feel I could apply a fairly decent clamping pressure.

I have some of the Bolduc wood glue on order from Pianotek. I think I'll use that for the bridge cap since I've read some good things about it, and I'm not anxious to get into hide glue.

I do have some West System epoxy (the G-flex stuff). It has a good 45 minute work time, so I'll try pressing it into the cracks on the treble bridge.

One of our rebuilders in Portland gave an excellent class on repairing small cracks at the base of bridge pins. Joe G. likes to use epoxy to fill the cracks, but with a twist.

He uses a soldering iron with a flat tip to heat the bridge pin, just a moment or two is plenty, and then uses a toothpick to apply a teensy bit of epoxy to the base of the warmed pin. The epoxy flows like water into the smallest of cracks. If needed, you can repeat until there is just a hint of epoxy on the face of the bridge, and wipe it clean.

Align the pin, of course, before attempting! But, this method is outstanding at making sure the epoxy flows where you want it to go. One warning; excessive heat can kill the epoxy's ability to cure and/or its stabilty in the long run. There is a fine line here. But, I must say it is the best method I've seen for this repair, and goes very quickly once you've tried it a time or two.

I would trust the epoxy over CA in this capacity, for the long haul. I'm still a little leery of the aging of CA glues. I would think that the strength of the epoxy, and its ability to fill voids with some density, would make it a better choice for this. Wood glues are not void-fillers; they are for gluing things together. I would use an aliphatic resin (..the yellow stuff) for gluing a bridge cap back on, but not for filling cracks, as it isn't meant for that job.

Choose one!
Choose wisely!

Bill Spurlock wrote an excellent article in the Journal about bridge refurbishment in the March, 1992 issue. In it, he recommends the WEST System epoxy #105 with the #206 slow hardener.