'Plastic Compatible' paint strippers

Discussion in 'Workbenches, including workshop techniques.' started by Steph Dale, 18 October 2020.

  1. Steph Dale

    Steph Dale Western Thunderer

    Afternoon all!

    I'm following up here with my little adventure building a relatively obscure Czech electric loco. I needed to strip paint from two plastic bodyshells and found that neither 'Modelstrip' nor Phoenix Precision 'Superstrip' are available any more, so it was time to try some new products. As will become apparent, the initial activities didn't go well. Here, therefore, are some thoughts on plastic compatible paint strippers...:

    First up, the rogues gallery. From this it's possible to at least say that I'm not likely to ever be a product photographer. I call this one 'Still life with IPA':
    20201018_121330.jpg

    For your interest, the prices of these wonderous products are:
    'Biostrip20' is about £10
    Deluxe 'Strip Magic' is about £10
    Expo 44500 'Modeller's Paint Remover' is about £5
    2.5L of 99.9% Isopropyl Alcohol (IPA) from APC Pure (other vendors are available) is about £11

    The method:
    In each case I worked the paint stripper into the surface using a 1/2" hogs-hair paste brush, leaving it for as long as the manufacturer stated for each of their products and then cleaning up as directed using either a hogs-hair brush or a toothbrush. In most cases this means 'with water'; with the 'Strip Magic' that means 'with IPA'. After cleaning the shells went into warm water with a little washing up liquid and were scrubbed with a toothbrush, finishing up with a little cream cleaner (this is probably the reason the mouldings have a 'bloom' on them - they're not dusty or powdery, just very matt!).

    And to the results, let's start with the Deluxe 'Strip Magic', a runny gel. For a start it's worth noting that this is slightly odd in it's application; in fact I'd recommend having a look on a YouTube video jqSQUqXcidU, which gives the full run down. It's certainly worth noting it's quick (about five minutes after applying I was able to brush off the paint with IPA), but the problem with that is that it doesn't have time to penetrate thick paint in and around detail. It also has a warning about leaving it in contact with bare plastic. And this is where I got into trouble. Applying a second coat of the stripper badly solvent-burnt the bodyshells, resulting in distortion to the surface; they're effectively useless, although did come in handy when evaluating the other paint strippers. I should also mention that I've no idea what the bodyshell material of these Atlas Editions models actually is; it doesn't feel like styrene as we would know and understand it:
    20201018_121807.jpg

    After this disaster I tried a blob of it on one of my test 'shells - the 1980s Piko models have very thick and tough paint which I've never managed to shift. The 'Strip Magic' was effective, removing one layer of paint at a time and didn't damage the bodyshell (well not any more than it was already). So in this application it was good, effective and safe. So the quest was on to find a stripper I can use on the second set of Atlas Editions 'shells when they arrive....

    Next up was Biostrip20 which is a white goo, with the consistency and appearance of runny icing. This was a complete unknown to me, popping up in my on-line search results and available from a well-known online retailer. In the reviews there were comments ranging from 'useless' to 'great', including one guy who was using it on military models. Worth a punt I thought.

    The photos below show a black diesel loco body that's had two applications of Biostrip20; there's just the odd corner where I might want another targeted application and most of the paint actually came off after the first application. The tan-coloured electric loco body shows this; the left hand half has had one application, the right hand half has had two. There might be a need for a further go around the grilles:
    20201018_121708.jpg

    From above you can see that I wasn't completely effective in getting the stripper around the roof detail on the electric loco; it's much more effective at the other end where the detail was removed before applying the stripper. You can also see green staining on the plastic; there's no paint remaining, but the pigment has been absorbed into the surface of the plastic in these areas. I think this is probably an effect of the moulding process opening up the surface of the material where it's injected into the mould - I'll bet their reject rates on this moulding were pretty high. There's a pink blob on the roof of the diesel; this is a gluey thumbprint under the paint, there are also a couple of other gluey marks around the scavenger (the grey disc), where the paint hasn't lifted properly:
    20201018_121737.jpg

    Next up is an honourable mention for Isopropyl Alcohol (IPA) on its own. From previous experience I know it's often worth trying IPA as a paint remover, I just completely forgot this time. It's perfectly adequate at removing factory finishes from US-outline locos (Athearn, Atlas, Kato, etc) and is generally not harmful to plastic; as my run-in with the Atlas Editions bodyshells show though, it's never safe to assume anything and I'd always suggest performing a test with any paint stripper on a plastic 'shell.

    The Expo 44500 'Modeller's Paint Remover' which is another thick gel, hasn't got beyond testing in this round. It proved completely ineffective on the Piko paint as with most paint strippers I've tried. It also had a strong effect on the Atlas Editions bodyshells so has not been short-listed for those either. However, I should mention that I have been in touch with Expo about its use on polyester and polyurethane resins, such as those used in the Finney7 loco kits and I expect it to be very effective for that.

    And to finish up, this is what happened when the Atlas Editions bodyshells were used to test the relative products. In each case a splodge was applied to a cab roof, or for the IPA test the whole cab end was dunked for an hour. In each case, the chemicals were left on the bodyshell as per their directions:
    20201018_121919.jpg

    Top left - first test with Expo 44500' Modeller's Paint Remover'. I thought I made out some softening, so...
    Top right - second test with Expo 44500' Modeller's Paint Remover'; definite softening of the surface.
    Bottom left (and everywhere else) - Deluxe 'Strip Magic'. Solvent burns, surface distortion.
    Bottom right - 'Biostrip20'. Softening penetrated a long way into the plastic - I was actually able to brush away parts of the model!
    Bottom left (2nd) - This is the end that got dunked in IPA for an hour, with no further damage occurring.

    Conclusion
    Always test your chosen paint stripper before a wholescale application. Different paint strippers are effective on different paints and on different substrates. The Biostrip20, in particular, managed to be both a hero and a villain in stripping the Piko bodyshells very effectively and causing the worst damage to the Atlas Editions ones. Use all these (and any others) with caution.

    It'd be great if we could keep this thread running with other people's experiences; I'll certainly add to it as I go. If you're going to mention a product, can you please be explicit about what it is, how much it costs, how you've used it, what you used it on and what you found. Hopefully we can then build up a little group knowledge for what can be a fraught experience.

    Steph
     
    Last edited: 18 October 2020
  2. Mike Trice

    Mike Trice Western Thunderer

    In the past I always relied on Caustic Soda which was cheap and did a reasonable job however where I had sprayed with Halfords' Primer it was not very successful. Since then I always turn to IPA and so far it has not let me down even removing the Halfords' Primer.
     
  3. 76043

    76043 Western Thunderer

    I've used this stuff for some years now, under a pound and available in Sainsbury's too. For some reason it won't strip Halfords red oxide, but does enamel and all other acrylics and rattle cans. Does take days, so I use an old Tupperware style sealed lid box. You don't have to immerse the whole lot in one go, but keep rotating the item so that the paint does eventually come off. Not have any trouble with any injection moulded plastic yet, from Dublo to Parkside.

    The only exception is Masak, which is outside the scope of the posting. It leaves a hard white residue which can only be removed with a glass fibre brush.

    IMG_20201018_190448.jpg

    I tried Dettol once, never again, left a horrible acrylic mess.
    Tony