Plastic Etching Dip?

[Lunajammer]

Is there something easier than sanding to roughen/prep plastic to receive paint? Ideally, I'm looking for something like a dip that might etch or dull the plastic. I'm actually considering steampunking a toy gun but don't want to sand around all the details. Need not recommend lacquer thinner.

[SfanGoch]

Get a cheap airbrush and use aluminum oxide abrasive powder. Same stuff as used to etch glass and metals.

[Ace-Garageguy]

Best method I've found (and swear by now) is an abrasive cleaner like Comet, mixed into a paste, and a stiff-bristled toothbrush. Scrub thoroughly, rinse in hot water.

Yes, it takes some effort, but it gets all the crevices around the details uniformly scuffed and dulled without softening the sharp engraving, and is FAR easier than doing it with sandpaper.

[Lunajammer]

Ooh, I like that idea. Especially when it comes with a testimonial. It's a big gun so I"ll still entertain other thoughts.

[Snake45]

Is there something easier than sanding to roughen/prep plastic to receive paint? Ideally, I'm looking for something like a dip that might etch or dull the plastic. I'm actually considering steampunking a toy gun but don't want to sand around all the details. Need not recommend lacquer thinner.

If I wanted to do this, I'd experiment with a spray solvent like a brake cleaner, carb cleaner (Gumout), or Gun Scrubber. In pure liquid form these would dissolve plastic, but misted on and let dry (and they'll dry quickly), they might give you just the effect you're looking for. As I mentioned, experimentation would be key.

[Ace-Garageguy]

One warning note (and I've discovered this by first-hand experience): when you break the shiny as-molded surface by scuffing, the plastic almost always becomes more sensitive to the hotter solvents in some primers and paints. The shiny as-molded surface is actually harder than the plastic immediately below it, and somewhat more solvent-resistant

I verified this again recently while prepping a Gunze Ferrari 250 GTO body for primer.

I thoroughly scuffed the hood with Comet, but left the backsides of several parts as-molded.

When I shot the hood with a hot self-etching primer, it crazed horribly. BUT...the un-scuffed backsides of the other parts showed very minimal crazing.

 

 

[Snake45]

One warning note (and I've discovered this by first-hand experience): when you break the shiny as-molded surface by scuffing, the plastic almost always becomes more sensitive to the hotter solvents in some primers and paints. The shiny as-molded surface is actually harder than the plastic immediately below it, and somewhat more solvent-resistant

I verified this again recently while prepping a Gunze Ferrari 250 GTO body for primer.

I thoroughly scuffed the hood with Comet, but left the backsides of several parts as-molded.

When I shot the hood with a hot self-etching primer, it crazed horribly. BUT...the un-scuffed backsides of the other parts showed very minimal crazing.

 

 

I think this is related to--if not exactly the same thing as--so-called "emblem ghosting."

[Ace-Garageguy]

I think this is related to--if not exactly the same thing as--so-called "emblem ghosting."

Yes sir. Same cause exactly. Excellent point.  

[gtx6970]

Westleys Bleach White will etch the plastic to some degree

[peteski]

Why do we need to sand plastic?  I good wash should work really well to get it prepped for paint. Of course if there are flaws or flash, that needs to be sanded off and smoothed, but no need to sand the entire body.  I have never sanded the entire plastic body before painting (but I do give them a really good wash in dishwasher detergent without any hand moisturizers in it). Organic solvent based paints (even the mild plastic-compatible ones) have plenty of "tooth" to bond really well to bare un-sanded plastic.

But if the plastic gun is made of some slippery solvent-resistant plastic, then I guess the only good option I see is to sandblast it.  I have a badger Air-Eraser (wuth aluminum-oxide abrasive powder) for jobs like that.  Then there is a adhesion-promoter which comes in a spray can.  It is designed to be sprayed on plastic car parts (like a flexible bumper cover) before painting it with the final color.

Edited August 16, 2016 by peteski

[SfanGoch]

If it's anything like the 1:1 replicas formerly made by LS, it's probably made from ABS. They weren't intended to be painted after assembly.

[astroracer]

 Get some ScotchBrite, the grey is a fine grade. Use that in place of sandpaper to get into small details and compound curves. I use ScotchBrite exclusively when prepping for paint unless there is a lot of blocking to do.

Mark

[peteski]

If it's anything like the 1:1 replicas formerly made by LS, it's probably made from ABS. They weren't intended to be painted after assembly.

ABS is a type of styrene plastic.  Organic solvent based paints stick to it very well with no scuffing (again as long as the surface is clean).   Some automotive models are also molded in ABS, as are model trains (and I had no problem painting either).

[Snake45]

If it's anything like the 1:1 replicas formerly made by LS, it's probably made from ABS. They weren't intended to be painted after assembly.

Huh. I've done a couple of those and I never had the impression that they were anything other than "normal" styrene. Although now that you mention it, I think the cartridge cases and maybe the bullets were made out of something "different."

Wish you could still get these. There are several I wish I'd bought when you could. They were always expensive. The first one I bought was $5 in 1972, when that was a LOT of money for any model kit. Later, '80s I think, they were $29.95 when THAT was a lot of money for a model kit. They had some cool stuff.

[SfanGoch]

ABS is a type of styrene plastic.  Organic solvent based paints stick to it very well with no scuffing (again as long as the surface is clean).   Some automotive models are also molded in ABS, as are model trains (and I had no problem painting either).

ABS is also extremely impact resistant, which is why it is used in manufacturing replica weapons which function like their real life counterparts when firing specially designed blank ammo. What I meant when I wrote that they weren't intended to be painted after assembly was that the parts were molded in colors replicating the different materials and finishes found on the actual firearms they were modeled after. The P38 and M1911A1 I had looked like they had blued finishes.

. 

[Snake45]

ABS is also extremely impact resistant, which is why it is used in manufacturing replica weapons which function like their real life counterparts when firing specially designed blank ammo. What I meant when I wrote that they weren't intended to be painted after assembly was that the parts were molded in colors replicating the different materials and finishes found on the actual firearms they were modeled after. The P38 and M1911A1 I had looked like they had blued finishes.

. 

The two I have don't look anything like blued finished, they just look like regular black plastic. So does this picture. I see you've got a pair of real postwar P.38 or P.1 plastic grips in that box. Cool! I built a real P.38 out of a cigar box of random parts, and use those grips on it. I like 'em a lot better than the WWII ribs.

[SfanGoch]

That's not mine. It's reference photo from a Japanese site. The P38 I had was purchased in Germany in 1982 in a department store in Wurzburg. I paid 15 bucks for it. The plastic on mine was a satin blue-black color. I sold it about a week later to our unit's XO, for $75 and his month's Class VI liquor and cigarette rations, which went toward the purchase of a used 1981 BMW 520i. The guy I was buying the car from wanted $2300 USD cash, 15 bottles of Jim Beam and 20 Cartons of Marlboros. The real "Art of the Deal".