Rehabilitation of an old Harmony archtop

harm1.jpg

Once I removed the back and had a good look at the insides I was puzzled as to what type glue was used.
First look said Gorilla Glue but I don't think GG existed in the 50's. One thing I found out was that it's not water or steam soluble.
Any thoughts as to what type of glue?

[Ben-Had]

I would've thought HHG. That's what's used on mine. Is that a repaired tape?

I expected HHG but was stumped when I could not loosen or soften the glue with steam.
The kerfed linings softened with the steam but the glue would not cooperate.

I thought the fabric was some sort of brace or served the purpose of crack prevention.

harm fab.jpg

[B. Howard]

It is a casein based glue. It is waterproof but will soften with heat. It was the main glue in early aircraft manufacture when they were spruce and canvas. Gibson was using this glue as early as the mid 30's and perhaps even earlier. HHG does not lend itself well to factory production settings for lot's of reasons.

[tippie53]

interesting
it may be some kind of support for cracking. Can't wait to see the next stage .

[MaineGeezer]

I think the lethal (i.e. the kind that is NOT the safe-strip) variety of paint remover will soften the stuff.

It is a casein based glue. It is waterproof but will soften with heat. It was the main glue in early aircraft manufacture when they were spruce and canvas. Gibson was using this glue as early as the mid 30's and perhaps even earlier. HHG does not lend itself well to factory production settings for lot's of reasons.

Brian,
Thanks for the info. I've never heard of casein and would venture a guess that many here are also unaware of its existence. I'm researching it and learning a lot of the ins and outs. So when you suggest heat as a softener would that include careful use of a heat gun? Heating blankets that we use on side benders?

John Hall, casein is used to affix labels to beer bottles. No wonder the labels may soften and disintegrate with water but the adhesive stays rock hard.

I think the lethal (i.e. the kind that is NOT the safe-strip) variety of paint remover will soften the stuff.

Geezer,
I'm experimenting with the un-safe stripper as we speak.

unsafe.jpg

OK, the project Harmony archtop acoustic tenor guitar. It's mostly apart with top and back removed from the sides, kerfed linings removed from the sides and the dovetail neck has been separated from the headblock.
Fretboard only partly removed from neck and has disintegrated in several spots. Obviously a replacement fretboard is necessary.

Where should I put my attention next?
How can I know if the arched top has become misshapen?
Is this guitar some sort of 'standard' form factor? 3/4 possibly? I'd like to makeshift a mold to work with. In my haste to get started,
I didn't consider making a paper tracing of the body before I started taking things apart. So what are my resources as far as getting a tracing or possibly a plan?

I'll need to know the scale length in order to use an appropriately sized replacement fretboard. Do I measure from the face of the nut to the center of
the 12th fret and then double that measurement for scale length?

Geezer, the paint remover I tried, Strip-Eez or something like that, packaged in a yellow/black metal container with a sh*tload of warnings printed in several languages did not soften the glue so next I'll try an old steam iron and hope for enough heat to soften the glue and get me through detaching the remainder of the fretboard from the neck.

Too bad Bill Cory hasn't written a book that outlines and lists chronologically the steps to rehabbing an old archtop......with photos.....

[tippie53]

I wish I know more about arch tops.

this is an interesting project from my side of the screen