I've come across an old Ventura guitar that I'm sure either saw the inside of a hot car or a hot Texas attic. Anyway, one of the braces on the soundboard is obviously loose and needs reglued. The bridge has also lifted at the bottom and will need reset.
My question is what type of glue to use. I've seen some of the raging debates on this issue but I figured that since I'll be working in the sound hold for the brace and I won't have the ability to get rid of the old glue, there is probably a glue that is better suited for this application. I just don't know what it is. Hot hide glue? I don't know and need some advice. I wasn't sure after reading the Cross Brace Top Wrinkle page on Frets.com which glue to use.
Also on the bridge, I think I will use the hot hide glue, but I don't know which gram strength to get. Any suggestions?
And while I'm asking, what is the best DIY method for heating the bridge glue to remove it. Clothes iron, heat gun? I'm afraid of damaging the finish if I use a heat gun, though I don't suspect a hot iron will do the finish any good either.
Only two choices for glue, either original Titebond or hot hide glue. You also do not have to clean the old glue out before regluing, that is just not needed or practical, new glue will stick fine.
If using hide glue forget the gram strength, just use quality glue that is sold by Luthier supply places. Mix glue and water to a thin but slippery consistency, once heated.
Whatever method you use to heat the bridge just heat the bridge, protect the top from heat.
I agree with Jim Bancroft on the glue. For the bridge removal, I use a clothes iron. But, I've made a protector from sheetrock, and covered the top with metal tape. It covers the whole top and leaves a spot for the bridge to be heated. I'll upload a pic of it. It cost me about $5 to make and I use it all the time, and works great.
Is this some inexpensive Asian guitar?
The glue to use when you cannot help gluing to old glue and you don't know what glue it was (especially when it's near-certain not to have been hide glue) is epoxy. Hide glue does not adhere well to other glues, and Titebond does not adhere well to any cured glue, including itself.
If you are asking about gram strength, and given that this is a cheap guitar, I think you should glue the bridge with Titebond.
When you reglue a bridge you're going to clean the old glue off before regluing anyway so Titebond or hot hide hide glue would be fine.
As far as glue adhering, I've never had a problem ever regluing braces and I never clean out the old glue. I've used hide glue on guitars that were originally glue with titebond and likewise titebond on instruments that were originally glued with hide glue. Besides it's pretty difficult to impossible to clean glue from under a partially glued brace.
I use Titebond for my builds. I have found, like Howard, it does not like to stick to cured glue. As for an iron, I like a good hobby iron for shrinking polymer film onto model airplane wings. This is an older iron that gets scorching and is variable all the way down to very cool.