I’ve always been hesitant to use CA, in part because I’ve seen it fail after lengthy periods, but most modelers seem to be unconcerned about bonds falling apart. Am I missing something?
Why do I think this? When I was in the cadets a CF-18 model (nicely done, too) was donated to our squadron and sat for up to five years in a display case. Over that time I watched it slowly deteriorate–including the missiles falling off. I can only assume that they were held in place with CA, which is designed, I understand, to eventually break up anyway. It makes a great instant-bonding agent for fiddly bits like landing gear, missiles, etc. but given what I’ve seen I’ve stayed away. Is this fear warranted or not?
However, I’ve never had something properly bonded with CA have a bond failure. That includes a ceramic coffee cup handle that has lasted nearly 15 years—including frequent microwaving—without the slightest sign of failure.
Bonded surfaces must be clean. Using clean as in “sterile.” Okay, a few bacteria are not a problem, but you get the point.
Also, accelerated CA is more brittle, and more susceptible to UV radiation. Long term exposure to even very low levels of almost any ketone will also cause degradation.
It less than accurate to call the CA bond brittle. It’s shock sensitive especially in shear. That’s often a good thing if you make a mistake as you can shear the bond with a #11 blade and usually pop the item loose. If you don’t shock the bond it will stay bonded for quite a long time. The bond is somewhat less strong if you use accelerator but for most applications its strong enough either way.
Another thing to consider when using CA is whether there is “bite” to the mating surfaces. That goes toward what the previous post said about shear strength. If you use CA, since it doesn’t melt and bond the two pieces, like plastic cement does with styrene, it’s best to increase the surface area, and strengthen the joint, by pinning it. For a figure, for example, we have an arm with a flat surface, and a shoulder with a flat surface. I would drill a hole in both pieces and use a piece of wire, and flow the CA into that joint. That will be stronger than the simple butt joint. But that is a principle of gluing, not just in modeling, but in carpentry and joinery. The more surface area, the more interlocking parts, the stronger the join will be.
As to brittleness over time, I have models I built 30 years ago, all styrene and all assembled with Testor’s tube glue. Some of those joins were good and are still strong; others, like field equipment on a 1/35 figure, have not held up, the joins have weakened, and the pieces have fallen off. So it can affect other kinds of glue as well.