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Painting styrene

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Painting styrene
Posted by Macman44 on Wednesday, October 14, 2020 7:28 PM

This has to be an obvious newbie question, but I haven't seen an answer yet.

I'm just getting going with building stuff including styrene strips and sheets , and am having difficulties with (brush) painting it.  Using typical acrylic paints (e.g. Model Master), it just doesn't work well directly from the bottle - it just goes on non-uniformly giving streaks and coarse brush marks, and requires several coats to get a reasonably uniform finish (which is rather thick by the time I'm done).

So obviously I am missing some essential technique, which is doubtless second nature to the experienced.  What is the recommended way to get acrylic paint to coat well on (usually white) styrene?  Should some kind of primer be used first - and if so, what?  How (if at all) should the styrene be cleaned prior to starting?  Do I need to roughen the surface with (xx-grit?) sandpaper?  Is there any type of paint that should be used?  Generally, what is the process that works and doesn't involve too many steps and complexity?

Any direct advice or pointers to appropriate articles would be appreciated.

Thanks,    Paul.

Tags: Painting
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Posted by SpaceMouse on Wednesday, October 14, 2020 7:40 PM

Macman44
Should some kind of primer be used first - and if so, what?

I use either white or gray 2X--primer and paint. 

Answers will probably vary.

Chip

Building the Rock Ridge Railroad with the slowest construction crew west of the Pecos.

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Posted by tstage on Wednesday, October 14, 2020 7:44 PM

Paul,

Are the acrylic paint bottles you are using "new"?  Or, have you had them awhile?  If the latter, try watering down your paints with a small amount of distilled water.

Also, make sure you are using good-quality brushes.  I get mine from either Michael's or an arts supply store and one's designed for the paint that I'm using.  That makes a big difference, as I have never had a problem hand-brushing directly from a bottle or getting streaks - i.e. unless I remove too much paint by overwiping it on the side of the bottle.

And when painting styrene with acrylics, I don't even bother using with a primer.  Lightly sanding the surface 320 or 400-grit can't hurt, as that will give the paint some extra tooth.

Tom

http://www.newyorkcentralmodeling.com

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Posted by doctorwayne on Wednesday, October 14, 2020 10:22 PM

Washing the plastic using dish detergent and not-too-hot water, followed by a thorough rinse with water and allowing it to air dry should help to give better results.

I never cared for Model Master paints - Testors should have discontinued them and gone instead with PollyScale after they bought the company, as it gives better results when applied with a brush.
Do not expect the paint to cover well in one coat.  By the time you've finished the first coat, the area where you began should be dry enough to add a second coat, and, depending on whether you're using dark or light colours, another coat may be required.

All of the railroad-owned structures shown below were brush-painted with PollyScale paints...

https://hosting.photobucket.com/albums/b399/doctorwayne/STRUCTURES%20%20PART%20II/.highres/SWITCHMANS%20SHANTY.jpg?width=450&height=278&fit=bounds&crop=fill

Same "company green" on the roundhouse doors, windows, trim, eavestroughs and downspouts, too, all applied with a brush...

I think that the woman who owns this restaurant must know someone who works for the railroad, too.  This DPM kit was moulded in a fairly dark blue-plastic, but the Pollyscale white covered it easily. (The structure is on the tracks only to facilitate photography.)

I also use Pollyscale for larger structures, but apply it with an airbrush.  This is faster than brushwork, and uses less paint, too....

Wayne

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Posted by compressorman on Thursday, October 15, 2020 8:11 AM
Vallejo Model Color are some fantastic acrylic paints for hand brushing. Try these and you will not look back. They airbrush well too if thinned enough.
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Posted by Overmod on Thursday, October 15, 2020 9:44 AM

doctorwayne
Washing the plastic using dish detergent and not-too-hot water, followed by a thorough rinse with water and allowing it to air dry should help to give better results.

Why this is so deserves a moment's further comment.

Parts made of polystyrene or a copolymer like ABS that are produced in injection molds require some 'help' to keep the hot plastic from bonding to the metal mold.  This is done with what is called a 'parting agent', and some of this remains on the plastic after it is cooled and demolded.  This is a reason paint that does not have a parting-agent solvent in its composition may not stick, and why removing the parting agent with suitable methods (hot water, detergent, brush scrubbing) is important.  

I believe some kinds of 'plastic' primer have the equivalent of self-etch materials that will dissolve parting agent and cause surface activation (as distinct from surface roughing-up as sandpaper does) of the plastic molecules.  Note the methods used in the consumer industry to treat polyethylene or other 'slippery plastic' bottles so that cheap labels will reliably adhere to them -- this can be as simple as brief exposure to electric plasma discharge.  Similar methods can make kit plastics amenable to painting... 

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Posted by MisterBeasley on Thursday, October 15, 2020 10:44 AM

I don't do enough scratch building or rolling stock work to justify an airbrush, but I've had good luck with rattle-can spray paints, either the expensive hobby shop specialty colors or an occasional large can from the hardware store.

Like airbrushing and brush painting, rattle can painting does have a learning curve and takes some time to be confident of your skills.  Clean surfaces are still important.  Two light coats are often better than one heavy coat.  I generally prefer to paint kits before assembly, and I often combine brush painting of details with spray painting of walls to get the look I want.

It takes an iron man to play with a toy iron horse. 

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Posted by wjstix on Thursday, October 15, 2020 10:51 AM

Any paint is generally going to work better if a primer is applied first. I would recommend Tamiya gray Surface Primer, you can get it in a 180 ml. can at your local hobby shop. Tamiya spray can paint uses a fairly fine-spraying nozzle, I'd say it's at least as good as a low to medium cost airbrush.

I have good luck using Acrilycos Vallejo paints for brush painting.

However, once you see how much faster / easier / better spraying is, I suspect you won't do that much brush painting. Tamiya paints are designed for military models, but many of the colors are very close (or, to my eye, identical) to many of the colors used for railroad models.

Stix
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Posted by kasskaboose on Thursday, October 15, 2020 12:02 PM

As already mentioned, def get cheap brushes and paint from a craft store.  Michael's is great for a wide variety of both.  They also have coupons!  

I suggest putting down two coats.  The first serves as a primer.  In otherwords, it as a foundation for the other coat.

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Posted by SeeYou190 on Thursday, October 15, 2020 12:39 PM

Macman44
Using typical acrylic paints (e.g. Model Master), it just doesn't work well directly from the bottle - it just goes on non-uniformly giving streaks and coarse brush marks, and requires several coats to get a reasonably uniform finish (which is rather thick by the time I'm done).

Hi Macman,

It sounds like you are brush painting directly over smooth bare white styrene plastic like Evergreen.

You are having three problems, and I will give you my best advice.

1) White styrene should be primed before brush painting. The surface had no "tooth", so paints will not go on smoothly. You could just spray on Dullcoat, but I prime everything, except railroad equipment, with flat black as a primer. Using flat black deepens the effects of shadows when you brush paint, and this gives the model more depth when viewed.

2) Model Master water soluable (acrylic) paints are garbage. You will have much better results using Vallejo or Citadel paints. The old Polly S line were also very good. I only use water soluable paints for brush painting, and I threw away all my Model Master Acrylics ages ago.

3) You need a brush suitable for model work. You did not say what you are using. If you have a Michael's nearby, the brushes they sell as suitable for "artist watercolors" will work well for hand brushing. Anything with stiff bristles will cause streaks and a rough finish.

Hopefully this will help you in the near-term.

Feel free to ask for more detail. I did not want to write too long of a response.

-Kevin

Wink Happily modeling my STRATTON & GILLETTE RAILROAD. A Class A line located in a personal fantasy world of semi-plausible nonsense on Tuesday, August 3rd, 1954.

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Posted by dstarr on Thursday, October 15, 2020 12:58 PM

Use rattle cans.  It is VERY difficult to avoid brush marks when brush painting plastic.  This started out as the Fisherman's Coop and Cannery from Railway Design Associates.  I split it into a pair of almost flats.  The brick is sprayed with red auto primer.  The roofs are dark gray auto primer. The window sash and doors are brush painted with Floquil lacquer.

   The advice to wash the model in hot soapy water and give it a thorough dry is sound.  Not only do you need to remove mold parting compound, you need to get rid of finger prints too.  Don't touch the model with your bare hands after rinsing it.   

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Posted by ctyclsscs on Thursday, October 15, 2020 4:54 PM

The advice about fingerprints is very good because not every molded part requires a mold relase agent. Plastic molders try to avoid using them if they can. BUT, parts are often removed from the mold by hand and packed into boxes. Then the parts are later removed and handled by someone packing the kit, so they are handled multiple times. Also, if the parts aren't packed right away, they can attract dust and other specks of this and that from static electricity.

Jim

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