Chemical Resistance of Polystyrene

[PatB]

I'm about to start the restoration of some old Triang bodies and, being a skint cheapskate, was researching "safe" alternatives to paint stripper when I found this useful table, listing polystyrene's resistance to various chemicals. 

https://www.google.com/url?sa=t&source=web&cd=10&ved=2ahUKEwjS9_La6azlAhWzILcAHTIeA9gQFjAJegQIAhAB&url=http%3A%2F%2Falwusa.com%2Fpolystyrene&usg=AOvVaw3cqK1b9EvrLd6380yi6M7i

As a result, I'm going to go with the old oven-cleaner-in-a-plastic-bag approach, as it seems a safer option than even isopropyl alcohol, let alone things like brake fluid or any of the organic solvent based general paint strippers (as opposed to model specific goos). 

 

Conversely, the table could also be used as a guide to select a suitable solvent adhesive. 

 

I'm also sure such tables are available for other plastics encountered in modelling. 

 

I know there are valid arguments for using the proper stuff. However, as noted, I'm broke (as usual), and, perhaps, more compellingly, I have one model shop within vaguely sensible distance. If they're closed, or if they go out of business, I'm pretty much stuck with what I can buy at the local DIY warehouse, at least as far as unpostable chemicals are concerned. It does no harm to undertake a little research into alternatives ahead of time. 

 

Edit:Oops, just looked again, and resistance to IPA is good. However IPA is expensive for enough to dunk a Jinty, so I'll stick with my $5 can of caustic oven cleaner. 

Edited October 21, 2019 by PatB

[Mark Saunders]

Not sure about what is best to use but my preferred route is Caustic Soda branded for cleaning drains, which is available in dry form as pearls/pellets and is cheaper than Oven Cleaner! 

 

Mark Saunders

[Darth Vader]

If your oven cleaner is in an aerosol can, then check to see what propellant is being used, most propellants are LPG, which is a hydrocarbon and will attack the plastic.

I assume that when you say restore, this means you would like to keep any painted surfaces intact and not clean the model to bare plastic.

Most paints used in Tri-ang models are fragile in that they can be removed with methylated spirit. This will not affect the body but will ruin any painted finish. So beware.

Whatever method you choose, I would recommend testing it on some Tri-ang model that if ruined will not be the end of the world.

 

[PatB]

Thanks for the input. I'm aware that raw caustic soda is cheaper, but I don't really have any other uses for it and would prefer to keep handling to a minimum and not have half a tub of hazardous stuff kicking around for ages. 

 

Good tip on the propellant, which hadn't occurred to me. I'll check the tin. 

 

I want to strip these all the way back to bare plastic all over prior to painting. They've suffered the attentions of a previous owner with a brushful of gloss black something or other, and I'd like a clean start to the necessary repairs so I've a chance of seeing what I'm doing. I'm not going for a factory finish as the surgery involved is just too drastic and will be very obvious without a fresh coat of paint.

 

Both the Jinty bodies involved, donor and recipient, are, basically, sacrificial. Neither is particularly rare or special. I'm doing this more as a learning exercise than for any logical reason. If I was going to be logical I'd be scanning Ebay for a better shell. So, whilst I'd prefer them not to dissolve in the process, it's not the end of the world if they do. I'm quite likely to botch the cut and shut anyway. 

[34theletterbetweenB&D]

6 minutes ago, PatB said:

...Both the Jinty bodies involved... I'm quite likely to botch the cut and shut anyway. 

I shall be watching closely to see if you are venturing on a Double Fairlie-Jintly. (Old style one piece tank loco bodies are rather inviting for this sort of thing, relatively easy to fit a low profile BoBo drive from the likes of a Heljan 15/16/17 inside.)

[PatB]

1 hour ago, 34theletterbetweenB&D said:

I shall be watching closely to see if you are venturing on a Double Fairlie-Jintly. (Old style one piece tank loco bodies are rather inviting for this sort of thing, relatively easy to fit a low profile BoBo drive from the likes of a Heljan 15/16/17 inside.)

 

Interesting idea, but no (unless my rapidly advancing addiction to buying broken rubbish gets still worse). Just a transplant of front bufferbeam, running plate and part of the valance on the side that's lost its forward steps, on a shell that, for some inexplicable reason, I happen to feel sorry for, donated by a shell that, for some inexplicable reason, I think should be cut up for parts, in spite of being, objectively, in better nick.

 

And, funnily enough, I do feel sorry for these locos as I gaze into my box of cracked and faded black and maroon plastic. There's a fair chance that at least some of them were the highlight of some long ago birthday or Christmas morning, making it rather sad that they are now only a step or two removed from the bin. It seems churlish not to spend a little time and effort to render them capable of providing enjoyment once again.

 

I do keep thinking of an 0-4-4 conversion, along the lines of something Golden Fleece, formerly of this parish, did with a TT Jinty. As far as I can see, it would work just as well in 00.

[34theletterbetweenB&D]

Of anciente tyme, blending the Triang M7 mechanism (ideally rewheeled with smaller drivers) with the Jinty bodyshell was the path to an MR-ish 0-4-4T that actually worked better than a more accurate  whitemetal kit version: because by packing it solid with lead ahead of the trailing driven axle, the CoG of the plastic bodied model ended up between the drivers.

[jonhall]

9 hours ago, Darth Vader said:

If your oven cleaner is in an aerosol can, then check to see what propellant is being used, most propellants are LPG, which is a hydrocarbon and will attack the plastic.

 

 

 

I would expect propellant to be a propane butane mix, which won't remain liquid for very long at room temperature and atmospheric pressure, certainly not long enough to melt triang plastic.

 

'Modelstrip' and the like is just Sodium Hydroxide in a clay or cellulose gel, which makes it a bit less likely to splash, and means you need less to strip paint. Oven cleaner works just as well, but do take sensible precautions, safety specs and gloves, wash hands immediately afterwards, and if you spill any, flush with LOTS of water ASAP. Last but not least, don't forget your school chemistry, add the alkali to the water because heat is generated!

 

Jon

Edited October 21, 2019 by jonhall
spellin

[PatB]

4 hours ago, jf2682 said:

In the past I have used model aircraft glow-plug fuel to remove paint and decals.  No smoking or naked flames nearby of course!  (unless the naked flame is of the female type of course...)

 

JF

Ah, the glorious smell of methanol, castor oil and nitromethane . I keep a bottle handy to remind myself what power smells like. I can't be bothered with getting the castor off afterwards though.