Stripping Old Paint
This is a topic which arises frequently on the rec.models.railroad news group, and many different chemical methods have been suggested.
Most of the paint strippers I have used when working on one of my cars will attack most plastics, sometimes quite visciously, and I did not wish to go hunting for expensive alternatives. However I had an old Hornby "Dock Authority" shunter which I had brush painted, badly, several times, many years ago. As a result it was so thick with paint you could hardly tell what shape it was! It had to be stripped.
To remove the paint, which was Humbrol enamel, I dunked the shell in a jar of old brake fluid which I had removed from some of my cars. I like to use silicone brake fluid for my brakes, as it doesn't absorb moisture and won't attack paint if spilled, but that means I have to remove the old "normal" fluid first, and it's not the sort of stuff you dump down the drain!
After a few hours the paint had almost entirely peeled off, and I gave the shell a quick scrub with an old brush before cleaning it. The screen printing was not disturbed, so the shell was nearly back to as-new condition, except that the buffer beams had originally been painted red. It is essential to remove all traces of brake fluid (or whatever other chemical paint remover you use) so I left the shell to soak overnight in a jar of water with some household detergent (washing up liquid) in it.
I have heard reports that brake fluid will make some plastics brittle, but it does not seem to have affected this old Hornby shell at all. The usual suggestion is to try any technique on a piece of scrap first, but if you want to know whether your favourite locomotive will be damaged by brake fluid, then you probably haven't got any "scrap" samples of that exact plastic to hand.
