Glue

[paddy]

Occasionally when handling older models ,or should i say models built a while ago, i notice they do tend to fall to bits
I recently took my 8 year old Triumph 3HW of the shelf for some pictures and bits were loose or had fallen off so i had some repairs to do before i could take pictures.
I have noticed this before. Things that were stuck firm have literally fallen off ?
Is it me i wondered ? but then it fell off its stand on my table so it just went from vertical on its tyres to lying on its side, no force whatsoever, and one of the foot rests snapped off. It didnt break at the join, it snapped half way down its length. Now as i was building a new example of the same model i took this part out of the box for examination.
The old parts is brittle it has very little structural integrity left at all. I t could barely support the weight of the model. The new part is 3mm in dia and like most plastics, its soft its actually quite bendable.
Other parts i found had just become detached, these were parts held together with, in this case, Revell cement made for the job.

Now in the past i have had all sorts of problems with parts self destructing on Italeri models in particular their vintage car series and i have pointed out the failings here before. It may be coincidence that this triumph is also Italeri

So i took a piece of italeri Sprue and drilled a small hole in it. I then dripped a tiny amount MIG wash in the hole. . Five hours later i tried to snap the sprue but it was strong, i would guess because of the short length i would have needed pliers to hold and brake it.
this morning, about 15 hours later...........it snaped like a twig in my fingers. there is no sign of stretch in the plastic, it just snapped at 90 degree to its length. See how the plastic has turned white, almost crystalised

I am now going to carry out a more scientific test with some pictures with different solvents commonly used in model paints and different makes of Sprue.

Why you ask ?
Well i have built models i would like to keep like my two recent Triumph motorcycles and its pains me that the first one is already degrading and bits falling off as i just finished the second one.

 

[moon puppy]

I think the Migs is solvent based and you're putting it on raw plastic so yea, it will degrade the plastic. Also bending the plastic to start with weakens it a bit, I would think.
This is why we prime something before putting all those solvents on the plastic. One problem I have, and I remember the old Swanny's website had articles about it, is glueing on top of a painted surface. In the case of a CA bonding you're actually bonding to the paint/primer, not the plastic. Same with a solvent based joint, you desolve several layers of paint and may not get to the plastic. He suggested scrapping away some paint to get a good joint.
Let's factor in the age of the glue also, I got some thick CA that is just a glob now, I really should get a little mini fridge for the shed to store CA. $300 for a fridge, 8 bucks for a tube of CA...not fast with math but that may take a while to get my money back.

I think the plastic has something to do with it, as you noted on your Grant, the Miniart stuff seems very soft, I've noticed it also. how are those things going to hold up over time?

 

[Heavens Eagle]

There are all different blends of styrene plastic as there are oils, and fuels. Different solvents will cause problems with them over time. I have found that the Italeri kits seem to have all kinds of trouble. I have some built kits that are over 30 years old and still fine. None of them is Italeri.

 

[Steve Ski]

What a stinker. I've never run into this on anything, yet. Now I'll be glancing over at the curio cabinet wondering what's gonna fail first, yikes!

Oh boy, my Harley is Italeri, the one for my latest dio. It's a good thing I'm pegging it solid to the base, cause I really don't fancy messing with it later down the road. The only way we're going to know is when it happens. Thanks for the intel, Paddy, a good heads up is always welcome.