Concertina

New Thumb Straps

The thumb straps that were on my concertina when I bought it were non-original and not very well-made. They were thin, unpadded, frayed, an ugly colour, and fit very poorly[1].
thumbstraps1

I have now made a new pair from a kit supplied by Concertina Spares. Here are the parts and tools laid out ready to start:
thumbstraps2
The thing that looks like a cheap Chinese wood chisel is actually a home-made leather edge-creasing tool.

The quality of the materials supplied in the kit were pretty good, though I was a little surprised at having to pay an extra £1.50 for the instructions (which were supplied as a PDF file on a CD).

One oddity regarding the instructions is that they seem to disagree with themselves about what type of glue to use. The page titled, "Tools and materials not in the kit," lists both PVA glue and impact adhesive. In fact you only need one type of glue and each has advantages and disadvantages. Most of the instructions tell you to use PVA and the procedure is based around PVA (i.e. apply it to one surface and then clamp the joint together until it dries), but in a couple of places they instead state that impact adhesive is a better choice because it produces a softer strap. If impact is the better choice, why not describe the process for using it instead?[2] My own research suggested that a brand of impact adhesive called "barge cement" is the best (strongest) glue you can get for leather, so that is what I used.

The main drawback I found with barge cement (other than its high cost), as with all types of impact adhesive I've used, is that when the two parts touch it sticks together instantly and immovably, so if you don't get the joint perfectly aligned first time you're stuffed. I also found it difficult to remove excess dried glue. It worked well enough though, and I'm pleased with the end result and confident that it's not likely to come unstuck. If I was to make another set I would be tempted to experiment with hide or rabbit glue instead, because I have read that if you work the leather once the glue has dried it breaks up into lots of microscopic crystals and the joint becomes very flexible without significantly compromising its strength.

Here's one of the finished straps:
thumbstraps3

They look pretty nice and are infinitely more comfortable to use. The screws in the photo are incorrect (the heads are too large) - that's something I'll rectify when I make the new wooden ends. My attempts at decorative edge-creasing weren't very effective unfortunately, probably because the leather is so thin it isn't able to compress much at all.

Time spent making the new thumb straps: about 2-3 hours, though it took longer by the clock because the gluing was done in about five steps, which meant 20 minutes doing something else while the glue dried between each step.

[1] It took me a while to work out that the reason my hands hurt after five minutes' playing was mainly because the thumb straps fit so badly I was carrying most of the weight of the instrument on my little fingers instead.
[2] Apply a thin even coat to both surfaces of the joint, wait for it to dry, assemble carefully (bearing in mind you only get one chance to get it lined up correctly) and then beat the joint fairly hard with a mallet. Clamping is not needed.

Comments

Sounds as though impact would have had a drawback for you in that once the leather had been beaten with a mallet it would have been even less likely to accept the edge crease.

I like the "Barge glue". Is it made of rendered-down barges? :)
It's certainly good stuff, but I haven't been able to find out why it's called Barge, or why their logo has a polar bear on it. It's made by a company called Quabaug.
If your research comes up with the best method of patching holes in the bellows, then I'm all ears. Attempts to patch mine so far have failed...
It turns out mine do have a few tiny pinholes in the gussets (found them by putting a lightbulb inside the bellows in a darkened room). I'm planning to try patching one on the inside with very thin leather and rabbit glue. Not sure how well that will work but it's got to be worth a try. It's possible to completely remove and replace gussets but not without removing the papers first, because they are glued over the gusset edges. You can buy new (reproduction) papers but then you lose some of the originality and the nice patina.

Do you know how old your bellows are and where/how bad the holes are in them? What have you tried doing to patch them? I've heard it said that bellows only tend to last about 80 years, and mine are well over that (if they are the originals, which I suspect they are). Complete new bellows are available, but they aren't cheap and IMO don't look as nice as a genuine antique set.
My bellows are only about 25 years old, but I have a bad habit of resting the bellows on my lap when I'm playing sitting down, and that has caused some leaks on the angles. The gussets are okay as far I can tell.

Part of the problem is trying to glue leather going round a corner. THe patches have mostly come loose again. (I think the leather may have been a fraction too thick)
The concertina spares suppliers sell thin leather with pre-skived edges that is intended for patching the top fold. This concertina.net forum thread is relevant to your problem (I believe it's quite a common fault):
http://www.concertina.net/forums/index.php?showtopic=14522
(Incidentally, let me know if you would like me to send you some dry hide or rabbit glue granules - I have lots of the stuff.)