Binding Cracks

A couple of years ago I fitted some W/B/W/B plastic binding on a Tenor Uke...I got the binding from Stewmac ..I made the binding up with acetone using the Stewmac teflon binding thingy they supply..It all went together great ..I used CA glue to attach the binding to the uke white side out with no problems, The uke was finished with shellac....Now I have noticed that there are multiple fine transverse hairline cracks all round the binding..I don't care too much co's I kept this one for myself..But I would like to know what caused it to happen

I've often wondered about binding , I've never done it but have done research . I dont understand how you can glue layers together and then bend them without stressing the glue joints at the bends.
It seemed to me that it would be better to glue each layer of binding one at a time. Each succsesive layer would be a tiny bit longer . Bending the W/B/W/B after it is glued seems like trying to bend plywood . The outside strip of binding would have to be longer that the inside strip so it would not be stressed . I know I must be wrong because from my research it seems most bindings are glued together first.

I can think of only two possibilities: either the plastic binding itself is cracking or the Shellac that is on top of the binding is cracking.
If the surface underneath a finish is moving around too much it tends to crack hard, brittle finishes. It's very common with nitrocellulose, much less common with Shellac. Perhaps there is something in the way that plastic expands and contracts that gives the Shellac a hard time.
Of course manmade binding found on Guitars that are 50 years old commonly show binding that is cracking and disintegrating. I would not expect that on plastic binding that is relatively recent though.

Michael N. said:

I can think of only two possibilities: either the plastic binding itself is cracking or the Shellac that is on top of the binding is cracking.
If the surface underneath a finish is moving around too much it tends to crack hard, brittle finishes. It's very common with nitrocellulose, much less common with Shellac. Perhaps there is something in the way that plastic expands and contracts that gives the Shellac a hard time.
Of course manmade binding found on Guitars that are 50 years old commonly show binding that is cracking and disintegrating. I would not expect that on plastic binding that is relatively recent though.

Click to expand...

Michael.... It's the outer layer of the binding with cracks not the shellac but only on the external bends the waist area is ok...I bonded the plastic strips together some months before I used it maybe that was the problem it could have got too brittle.

I find this report a bit troubling (Oh no! Something new to worry about!) since I use this stuff a lot. I've found it to be extremely pliable and almost rubbery. Takes tight bends no problem... I think Pete's point about the outer ply bending more than the inner band has merit. As the top expands and contracts, the outer band would give in first. But this stuff should expand and contract a lot and this plastic really should not get brittle with age especially since it is sealed.

What size did you use Timbuck? The really thin, small stuff or bigger? The 0.01 or 0.02 or even bigger? Is the shellac above the cracks cracked? Did you heat it as you put it on? So many questions! Pictures would be nice Timbuck.

wood, ca glue, shellac and plastic bindings all shrink at different rates???

I've heard of nitrocellulose plastics shrinking over time....but I think Stemac's white binding is ABS. I think it should be pretty stable stuff....I don't recall any other cracking threads on the other luthier boards over the years.
Does it see a lot of sunlight? (not that anything really sees much sunlight in the UK yuk yuk yuk ) UV can be bad for ABS depending on the resin blend