How to fix a hairline crack . . .

[Tony M]

Hi, all.

Just got a new box (well, new to me, anyway) - Paolo Soprani 120 bass CBA.

I'm very pleased with it, it came at a good price and is in nice condition inside and out. However, I have a critical eye, and have spotted a hairline crack on one corner of the treble end bodywork, running down the corner to the point where it meets the bellows. No air leakage, no "movement" in the crack and no effect on playing quality - it really is a very fine crack and almost invisible. On the inside, it's the same story - but the crack is clearly there, nontheless.

I could leave it alone (if it ain't broke . . .) - however, my usual approach is that if it won't get better, fixing it might be a good move.

I've thought about gluing it:

I could use a thin mix of old-fashioned pearl glue (hide glue, if you like), which would be preferable from the perspective of being removable in the future. Thinned PVA might be another alternative - but the crack is so fine that I'm not convinced that either would penetrate sufficiently to achieve a good joint. The crack is pretty tightly closed, and there seems no point in trying to force it open to insert glue.

The only thing I can think of that is likely to penetrate is thin superglue. In general, I prefer to avoid the stuff, because its rather "one shot" - once it's on, there's no way to unglue it if the need arises.

So, I thought I'd seek a wider view and throw it open for discussion here.

Thoughts welcome.

Tony M.

 

[Soulsaver]

Hi Tony, I'm going to leave this to the pros on here... but I'm sure they'll ask, is it a modern constructed box?

 

[Tony M]

Hi, Soulsaver.

I would guess at 1980s to 1990s.

It's a 4 voice musette box, and not the latest (Internationale) version.

It has two bass couplers and 9 on the treble (no repeats). The soundboards and treble cover appear to be aluminium, the treble pallets are plastic, and the reed valves are leather. Treble cover is held in place with two spring-loaded buttons. There's a set of sound holes behind the treble keyboard, which suggests that it might be a common body with a five-voice version, perhaps.

I'd welcome info about its age, model, whatever, just for interest.

Cheers,

Tony M.

 

[Soulsaver]

We'd definitely need a pic for that, Tony.

 

[Tony M]

Good point!

Since you ask . . .






(Not taken by me - copied across from the sellers advert - so I hope he doesnt mind!)

Cheers,

Tony M

 

[Soulsaver]

Nice. The grill + the black background in the badge & the caps for PS, I believe would make it late 1960s, maybe early 70s.
I had a PA the same.

 

[rbs]

Could you use nail varnish?

 

[Tony M]

Soulsaver: Thanks for the info. It's nice to know these things. (Wow - look at all those bass couplers!)

rbs: Nail varnish will restore the finish on the outside (very effectively, too - it polishes down a treat), but I want to stabilise the crack first, since there's a fair chance it will increase in length as time passes - eventually to the detriment of the box.

Cheers,

Tony M.

 

[Soulsaver]

Yep - it was a Super Paolo without HM reeds & cassotto - forerunner to the Profesionale range. They come up now & then with people claiming thay are SuperPs.. for twice what they are worth. Nevertheless a lovely instrument, whopping big reeds in the bass..

But back on topic... have a look here: http://www.accordionrevival.com/ACCORDION_REPAIR1.php#Repairing_cracked_or_broken_wood

 

[Tony M]

Soulsaver,

Thanks for the link. I'd looked at that one yesterday, and it's good info (and exactly the situation I hope to avoid!). His pic shows precisely where I've got the hairline crack, and his approach to clamping is ideal.

He describes starting with a 1/8" gap - which makes it a big problem (from the instrument viewpoint), but easy to get glue into the joint.

My joint is pretty tight, and actually getting the glue to where it's needed is the difficult bit. (In fact, mine looks pretty much like what he ended up with after he'd fixed it!)

I've used many different glues in the past (I used to do a lot of model aircraft stuff), and, in digging around, I've come up with another possibility that I first used years ago: Deluxe materials "Super Phatic", which is a very thin, and highly penetrating, aliphatic resin wood glue. It's a mixed blessing on very soft balsa (which absorbs the stuff rather too much), but should work very well on the relatively hard wood of the accordion.

Another technique I've used is to mix so-called "5 minute epoxy", then thin with solvent (alcohol or cellulose thinners) - this allows the glue to flow (and to soak into very soft woods) but slows the setting time considerably. I'm less keen on that approach for this repair, because, if it fails to set properly (which has happened to me once or twice with this approach) there's no way to clean it out to try something else.

Still thinking carefully at the moment!

Cheers,

Tony M.

 

[Soulsaver]

I think the key to your solution is not to worry about the crack itself - as you say, it doesn't leak. What you need is to stop it opening further - like the inner supports in the link. Then with support either side internally to stop it opening, a cosmetic repair on the outer (nail varnish) et voila - good as new!

 

[Tony M]

Well, I've just had another look at the corner in question:

First off, it looks as though the construction on the Paolo is slightly different to the photos in the link (earlier) - there's more thickness at the corner, and there appears to be a fairly significant piece of wood at the corner itself (so it's not just the meeting of thin sections). This is the same at each corner. This corner block is machined out to match the bellows. If I was to attempt glue in the crack, I'd be feeding glue into that block, there's more to "glue to" , as it were (so there may be no need for reinforcement at all.

Secondly, and possibly more significantly, it's not clear that there's actually any movement in the apparent crack (not that I want to apply much force to find out, of course!). On top of that, looking at the outside, there's only a faint mark to see - I only noticed it at all because of the slight change in the reflections of light around the corner. The crack itself doesn't seem to be open on the outside at all - there's just a slight disturbance to the surface curve of the box that shows its line. This leads to the possibility that the thing was fixed a long time ago, and only the slight imperfection in the outside curve allows it to be noticed. In that case, your suggestion of nail varnish and some careful polishing will remove all traces.

On that basis, I think I'll take the "If it ain't broke, don't fix it" route - I might re-finish the outside as suggested. Nothing is lost that way - if it never gets worse, the box is fine, but if it needs a fix at some point, I haven't done anything to limit the possible approaches I can take.

One thing I note - no-one has come in and said anything along the lines of "whatever you do, don't do that!" - so perhaps I haven't suggested anything completely inappropriate!

Cheers,

Tony M.

 

[Soulsaver]

In the absense of any other input, that sounds the logical route to me. There's nothing more frustrating, for me at least, than trying to cure something that is an issue... but not really a problem...and ending up making it one.
When doing it myself, as a policy I err on the side of the least invasive route first.. always assuming that route doesn't preclude any other options.

 

[kimric]

Epoxy will thin nicely with Acetone, but use it sparingly as it makes the epoxy a bit weaker.

 

[the boxman]

hi

How about this, creeping crack cure it is very thin like water, you just keep filling the crack making sure to wipe off any that spills over.
http://www.amazon.co.uk/s/?ie=UTF8&...vptwo=&hvqmt=b&hvdev=c&ref=pd_sl_6tekxpuyfy_b

 

[Tony M]

Thanks for the replies.

Epoxy will thin nicely with Acetone, but use it sparingly as it makes the epoxy a bit weaker.

Agreed - a variation on what Ive used in the past. Your point about strength is well-made, too (it mattered little on model planes, since the glue was almost always stronger than the wood!). Acetone would evaporate far more quickly than alcohol or cellulose thinners, too. The only thing Id be concerned about is the potentially awful consequences of getting it onto any other bits of the box! I think, on balance, the thin aliphatic is probably safer, being water-based and wipe-clean.

How about this, creeping crack cure it is very thin like water, you just keep filling the crack making sure to wipe off any that spills over.

Its primarily a silicone sealant, as far as I can see - designed to stop water getting into places it shouldnt. It might be OK for that (although not all the feedback is positive), but I doubt if theres much structural strength to it. I suspect that it would be a one shot item, too - once it is in there, it is likely to make any attempt to use anything else very difficult - so Id be wary of trying it.

Nevertheless, the input is much appreciated.

Cheers,

Tony M.

 

[the boxman]

Hi

Its not a silicone it forms a strong bond. I have used this on a GRP repair and bonded the crack together, also used it on a cracked acrylic caravan roof window and again formed a strong bond and has held now for over 2 years and is exposed to all weathers. I is more like a watered down PVA but obviously a lot stronger.

Why not just use a pva. the accordion body is made of wood so this is probably the best to use.

Good luck with what ever method you use, all plenty to pick from and im sure they will all work.

 

[Tony M]

Its not a silicone it forms a strong bond. I have used this on a GRP repair and bonded the crack together, also used it on a cracked acrylic caravan roof window and again formed a strong bond and has held now for over 2 years and is exposed to all weathers. I is more like a watered down PVA but obviously a lot stronger.

Why not just use a pva. the accordion body is made of wood so this is probably the best to use.

Thanks for that correction - useful to know.

Interestingly, the Deluxe Materials Super phatic stuff is, similarly, very like watered-down PVA and is designed to penetrate - for all practical purposes, there seems little difference between PVA and aliphatic resin, although aliphatic may dry harder and is perhaps easier to sand. Its even possible that Captain Tolleys is the same stuff as super phatic - but comes in bigger bottles (and probably cheaper!).

If I decide to do anything with the box, Ill probably use the super phatic, since Ive got some to hand. It would make for an easy and clean job, with little disaster potential.

Thanks again,

Tony M.

 

[kimric]

I would use the gap filing version of super glue available at wood working and hobby stores. I have had really good luck with this. http://www.utrechtart.com/ZAP-ZAP-A...currency=USD&gclid=CJmy2rWbucECFcRcMgodfREAqA