With similar guidelines to what Wayne suggested, I only prime stuff that is black to begin with, or very multicolored, especially if a large part of it is black.
I use almost exclusively Scalecoat and Scalecoat II.
I have also successfully primed over existing paint schemes and repainted equipment without stripping the old paint.
I really hate stripping paint........
Sheldon
Some rattle can pans indicate they will bond to plastic. If I'm using one of those I don't prime. Otherwise I do. For my boxcars I use a red oxide Rustoleum primer as my finish coat. The color is very similar to many of the box cars in my fleet.
I prime everything before I paint it.
That is the way I was taught to paint, and I have never done an experiment to see if it really makes a difference.
-Kevin
Living the dream.
Thanks for the responses, everyone. I usually use a light coat of rattle can gray primer before painting anything. I have Polyscale and Badger Modelflex, as well as Testors Model Master acrylic paint. I do have an airbrush, though I am not very skilled with it. I have used craft acrylics for buildings, both brush and airbrush, though I will thin them for the airbrush.
I have used dark gray and red rattle can primers for freight cars in the past, but I was going to paint some different colors and was about to paint everything light gray primer first when someone asked why I was bothering. I suppose it can't hurt to try it and see how it works without primer.
Gary
I usually apply a spray coat of primer before the color coat. Most spray paints will cover styrene without issue, but there are cases where the finish color will craze the plastic if applied directly to it. Any metallic paint (e.g. silver/aluminum) is likely to damage plastic, even the newer Rustoleum 2X paint with built-in primer. I always use primer before applying metallic paint.
Rob Spangler
Rattle cans. Krylon or Rustoleum. Auto primers. The auto primers will stick to anything, even metal, cover anything, and dry dead flat. Red auto primer makes a fine boxcar red, a fine brick red, and a good color for trucks, which ought to show rust-red. Dark gray or light gray auto primer is a good color to put on the undersides of rolling stock, it covers up shiny metal car weights, shiny brass brake rodding, shiny screw heads, and too glossy plastic. Light gray auto primer is good for covered hoppers. Dark gray auto primer is just right for steam locomotives, far better looking under layout lighting than engine black.
I decal right onto good flat auto primer and they go on and stay flat. A top coat of Dullcote blends the decal right in, cuts the gloss from the decal film. Many say that you have to have a gloss coat under decals. I get good results decaling right onto dead flat auto primer.
I don't bother with a primer on wood or plastic models. All paints have no problem sticking to wood and plastic, especial if you do good surface preparation. Wash plastic in hot water with a little dish wash, Dawn is good. Wipe wood down with a tack rag, old rag soaked in a little varnish and a good deal of paint thinner. Gives you a sticky rag that picks up sawdust well.
One exception. If I want to paint a light color, yellow say, over a real dark color, black say, then I might use a coat of light gray auto primer. The light colors cover better over the light gray than they do over a real dark color.
I do use auto primer on metal. Good surface prep is a wipedown with alcohol or paint thinner to degrease the surfaces. Pickle the whole thing in a mild acid, supermarket vinegar works for me. This etches the metal and provides some tooth for the primer to grab onto. Finish the pickling with a good water wash. Gets the acid off so it won't mess up the paint.
David Starr www.newsnorthwoods.blogspot.com
If you wash the model, using dish detergent and warm water, then rinse it thoroughly and allow it to air-dry, many paints will work just fine on styrene without need for a primer.
Some exceptions might be some varieties of craft paints, which are often meant for use on paper or other absorbent materials, and brush-applied lacquer-based paints, such as Floquil. The latter will stick to the plastic very well, because it will attack the surface of the plastic, often leaving a pebble-like surface. Airbrushing lacquer-based paints yields much better results, as the paint dries-to-the-touch almost instantly.
Most acrylic paints work well on styrene, and the better quality ones (my favourite was the former PollyScale paints) can yield great results when airbrushed or brushed on with a good quality brush.
I often primed unpainted or stripped models that were cast in black plastic using Floquil's Grey Primer, as it provided a neutral colour onto which pretty-well any colour, including white, could be applied.
Another good reason to use primer is when you have a model which consists of many different-coloured parts, such as a black styene boxcar to which you've added grey doors, a brown roof, white placard boards, and brass grabirons. Like the all-black boxcar, the primer will give you a uniformly neutral background onto which any colour can be applied, and when dry, will be uniform in appearance.
Nowadays, if I'm painting something cast in a colour other than white or light grey (or maybe cast in a colour similar to what I'm using to paint), I'll give coat of grey primer, using either Tamiya's rattle-can version or a similar grey from Alclad, which is airbrush ready.
Wayne
I use Scalecoat II and no primer is necessary, although I may sometimes use a light gray or silver light coat if the finish color is light like white or yellow and the plastic is brown or black.
Rick Jesionowski
Rule 1: This is my railroad.
Rule 2: I make the rules.
Rule 3: Illuminating discussion of prototype history, equipment and operating practices is always welcome, but in the event of visitor-perceived anacronisms, detail descrepancies or operating errors, consult RULE 1!
I usually paint theses kits with rattle can spray paint, no primer. But, I am not a rivet counter.
It takes an iron man to play with a toy iron horse.
I've been building down my supply of kits lately, including some Tichy freight cars. Tichy kits are molded in a light gray polystyrene. I have also stripped some freight car kits and locomotives to repaint.
I was taught to always use primer to give a project some "tooth," for the finish coat to hang on to. Recently, though, I read somewhere to just paint right on the styrene, as to not overpaint details.
I'm curious what most folks do for painting plastic kits.