how to "smoke" clear plastic?

I have a clear plastic shell. I don't know exactly what sort of plastic it is, but it's probably not polycarbonate; it was cheap (bought it at
the dollar store).
I need to paint this with something that will make it look like smoked plastic. Some sort of translucent black paint? I will have lights (LEDs) inside, and the goal is that these lights should show up clearly when lit, but be completely invisible when dark.
But dammit Jim (*), I'm a roboticist, not a modeler. I haven't painted any plastic since I was a kid. So I'm hoping some kind soul here can recommend a specific paint and application technique that is most likely to work, even in the hands of a newbie such as myself.
Thanks, - Joe
(*) That's a Star Trek (original series) reference, for the folks here too young (or insufficiently geeky) to remember!
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Joe Strout wrote:

This isn't usually done with a paint, needless to say. I would try using a dark blue or black model paint, thinned somewhat. You'll need to experiment. Try some of the Testors acrylic model paint, with the appropriate thinner.
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Joe Strout wrote:

Most craft stores have a selection of semi-transparent paints for projects like faked stained glass. I'd try that first. Though they're usually in colors, I'm sure they have a gray.

What remember!?! The whole three series is on DVD. Just in time for a new generation.
-- Gordon
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refer to the Tamiya PS range for painting clear Lexan RC car body shells, especially PS-31 e.g. http://www.acehobby.co.nz/ossb2/root/OSSBEC3/showitem.asp?PID )137
refer also to: "Paints, Colour Charts, Mix Formulae & Strippers & How to spray F/Glass and ABS plastics " on my web page or email direct for a copy of "Tinting Clear Canopies "
Regards Alan T. Alan's Hobby Model & RC Web Links http://homepages.ihug.co.nz/~atong

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Well, FYI, I've tried dying the plastic with Rit black die, and it certainly tinted it, but not nearly as dark as I need. This was after what seems like extreme measures (left it in a hot dye bath for a couple hours, and then turned the heat off and left it in there overnight).
I'm trying it again with triple the dye concentration (i.e., dumped in two more packets of die), and had brought the water nearly to a boil before putting the shell in, which I'm going to leave until at least lunchtime. I also added a bit of vinegar to the mix, since one poster I found on the web claimed that this makes the dye work better. So we'll see, but after last night's experience, I'm not too optimistic.
Assuming this fails, the next step will be to try a translucent paint. Tamiya's PS-38 Translucent Blue might work, though I'd prefer black. One concern I have about this is the warning "Never use these paints on plastic models" (they're made for polycarbonate). I doubt my shell is polycarbonate... will the paint just not bond well, or what?
Another possibility is this "Nite Shades" translucent black paint made for automotive use: <(Amazon.com product link shortened)>
Any other suggestions?
Thanks, - Joe
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There are many types of plastic, some stain easily but others like PET will resist all forms of dye. A matter of try and see. The best paint to make windows appear black is the Tamiya Smoke PS-31. A light application gives a tinted window effect but extra layers build up to a black finish as used on the canopy of my large RC Bucker Jungman.
Regards Alan T. Alan's Hobby Model & RC Web Links http://homepages.ihug.co.nz/~atong

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wrote:

Aha. Maybe this shell is PET -- it certainly is clear, tough, and seemed to resist heat just fine, all characteristics of PET. And yes, it was very resistant to the dye too.

Thanks, that sounds good. I'm still curious about the "Never use this paint on plastic models" warning though -- will it just not stick, or start a fire, or what? I'm willing to try it and see what happens, as long as it's not likely to be dangerous.
Best, - Joe
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Joe Strout wrote:

remember to spray from the inside as its matt and very light coats as it will run
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Joe Strout wrote:

The "plastic" they're probably talking about is styrene, which is unlikelt to be what you're using. The warning is likely because the paint has solvents that are unnice to styrene. The same solvents may affect acrylic, so I'd test it first.
That said, I still think you'll do better with common, cheap transparent and semi-transparent paints made for crafts. Don't you have a craft store near by you can stroll through? Deco is a major brand.
Or, look in the Yellow Pages under plastics and find a local shop that does the smoking for you. May be cheaper in the long run.
-- Gordon
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Fair enough.

Well, yeah, but it's not clear to me how I would use these. Normally you use these on a flat horizontal surface (or so I understand it). This is a curved surface, half a giant Easter egg. If the paint is thin, it's going to run right off and make a puddle in the middle. If it's thick enough to stick to the sides, it seems like I'd have brush strokes galore. (Maybe this is just a skill problem -- a more experienced painter might know how to avoid that.)
Incidentally, I didn't find any Deco product that seemed appropriate, but I did find one called Gallery Glass that I think is the same thing as what you're suggesting: <http://www.plaidonline.com/apGG.asp
Maybe this Charcoal Black "Window Color(tm)" in particular: <http://www.plaidonline.com/productDetail.asp?itemID 018>
As you can see in the sample to the left, it doesn't go on very evenly, even in expert hands... but maybe I can live with that. They do say it can be applied vertically, which sounds promising.

Hmm, I looked for window tinters but those guys seem to work only with glass; I don't know that their stuff would work with plastic. A plastics shop is a good idea. Though I can hear the conversation already: "Well, what kind of plastic is it?" "...um... clear and hard?" :)
Thanks, - Joe
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Joe Strout wrote:

A beginner's airbrush set is pretty cheap. That and acrylic paint doesn't leave much brush strokes and applies evenly. As mentioned by someone else here, if you paint on the *inside* you should have better results. The best is to just do it.
Look under PLASTICS in the yellow pages for plastic fabricators, plastics retailers, etc. Tinting/smoking plastic is a common thing for most of them. They won't expect you to know what kind of plastic it is. That's their job.
-- Gordon
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wrote:

Thanks, Alan, I'll try that. Getting an even coat on a curved surface, without making it too dark, may be a little challenging... but fortunately, these plastic shells are cheap, so I can afford to ruin a few if necessary.
Best, - Joe
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Joe Strout wrote:

Paint will be difficult to apply in a uniform manner necessary to produce a controlled level of light attenuation. Can you apply some tinted film to the inside of the shell?
Contact an outfit that does auto window tinting to see what might be available.

--
Paul Hovnanian mailto: snipped-for-privacy@Hovnanian.com
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Paul Hovnanian P.E. wrote:

the Tamiya paint is easy to apply just apply in very light coats
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I can't see how I could apply tinted film to a curved (ovoid) surface without wrinkles galore. However, I'm currently trying a spray-on window tint from Testors:
<http://www2.towerhobbies.com/cgi-bin/wti0001p?&I=TESR2949
I did about twenty coats last night, each very light because otherwise this stuff tends to run. It's not quite as dark as I want yet, but other than that, it looks great.
Best, - Joe
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