Best Way To Apply Solvent Type Plastic Cement

[peteski]

Yep according to Intermountain guys way back when we had roof walk separation on some new box cars, they told us that CA will not stick to itself second time around.
It either needs to be totally cleaned off or another type of adhesive used.
Rod.

Like I said, I have never head that, or had that problem. I sometimes even layer multiple coats of CA to build up its thickness (when using it as a filler).

CA (Cyanoacrylate) is simply a type of acrylic (plastic, like Plexiglas).  If you apply some liquid CA over a layer of hardened CA, leave it sit for a while, then wipe it off while still liquid, you should see that the liquid stated to sightly dissolve the hardened CA. So adhesion should not be a problem. Sounds to me like there was something else in play for the Intermountain guys.

[Onizukachan]

Isn't there a problem with getting new CA to stick to already cured CA?  That would seem to say that you probably can't use CA for a joint that you may need to repair if it breaks from use.

It isn’t the stick, it’s that it is weaker. That where that recommendation came from 30+ years ago. Like a long game of telephone the original comment has become distorted.

[Maletrain]

My only (maybe) relevant experience was in trying to repair a living woody plant with CA.  I had read that surgeons used it instead of thread to close incisions, so I thought I would try it on a wounded limb.  The first application held for a bit, but broke under stress from a breeze.  A second application would not even stick enough to hold for a moment.  Probably not a proper application for that product.  But, having since been the recipient of a surgeon's CA closure technique, I can attest that it works fine on people.

[peteski]

My only (maybe) relevant experience was in trying to repair a living woody plant with CA.  I had read that surgeons used it instead of thread to close incisions, so I thought I would try it on a wounded limb.  The first application held for a bit, but broke under stress from a breeze.  A second application would not even stick enough to hold for a moment.  Probably not a proper application for that product.  But, having since been the recipient of a surgeon's CA closure technique, I can attest that it works fine on people.

From: https://en.wikipedia.org/wiki/Cyanoacrylate

Cyanoacrylate glue was in veterinary use for mending bone, hide, and tortoise shell by the early 1970s or before. Harry Coover said in 1966 that a cyanoacrylate spray was used in the Vietnam War to reduce bleeding in wounded soldiers until they could be taken to a hospital.[

[randgust]

In fairness, you'll have the same problem with solvent cements - they are designed to be a solvent on the native material, not the dried glue itself.   If you want to get a firm bond from a broken joint you really need to scrape clean the original joint down to plastic if you can.  When I'm making molds the air bleed lines are typically .035 Evergreen rod, lightly glued to the surface of the master.   They frequently break off when the mold it first removed from the master and have to be re-applied to make another mold.   SOP is to clean both surfaces as simply doing more glue on the original joint doesn't work very well at all.

My first experience with the 'miracle' of ACC was back in the 1970's when it first came out.   I had a snowmobile, and the glass headlight bulb actually broke out of the brass socket, yet was still working just dangling on the filament wires.    I got my 'model train' new ACC out and tried to glue the bulb back in the socket.  It actually worked.  And it never came apart over several more years, machine was sold with that light bulb still glued together.  Amazing stuff.