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Question about to primer or not to primer


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I am unsure if it is necessary or at least recommended to use a light coat of primer in order to paint a car body molded in white with a gloss turquoise enamel.  I know that primer is kinda required for painting a dark modeled piece with a lighter color, just not sure if with white modeled its really necessary.

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If the body is clean and prepped and possibly roughed up a little with a Scotchbrite pad or something similar, and if your paint is good and applied correctly, and you know what you're doing, you can get away with it.

I could probably get away with it, for example, but I can't promise you that YOU can. Good luck! B)

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I always use a coat of primer on every model. No matter how well I think I've done my bodywork I always seem to find a mold line or something that I just didn't see. I would rather catch it when it is in fast drying primer and easy to fix than when I put a color coat down.

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If painting using hobby paints I try to avoid primer as much as possible (to minimize paint thickness).  If using hotter paints, primer is needed to act as a barrier to prevent the hot solvent in the paint from crazing the styrene body.

 

Of course if the plastic body is bright red and I want to paint it white, I will use primer, or even additional barrier coats, even when using hobby paints (to prevent the red plastic dye from bleeding into the white paint).

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Mythbuster Alert: Color does not "leach out" of plastic. That's an old superstition.

I've got a beautiful pink shade of primer on a 1/20 scale Chevrolet suburban kit that would argue with you about that, three good coats of duplicolor gray primer and it's still turning pink when it dries. Time to hit it with B.I.N. sealer.

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I've got a beautiful pink shade of primer on a 1/20 scale Chevrolet suburban kit that would argue with you about that, three good coats of duplicolor gray primer and it's still turning pink when it dries. Time to hit it with B.I.N. sealer.

If pigment can leach out of plastic, then there should be some chemical you can soak the plastic in that would leach ALL--or most, or even a visible amount--of it out. Show me that chemical and I'll admit I'm wrong.

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It all depends on the results you would like to achieve.  If you are happy with mediocre results, soldier on! It's just a hobby.  If you sincerely want a nice to superb finish, there are no short cuts.

I'm not the best painter, but I do prime EVERYTHING.  For nice results, one must clean up the body. That means sanding out imperfections, mold lines, ejector pins and filling in depressions with putty and such.  For the life of me, I cannot see the result of this work in raw plastic, but the work I still needs to do is very evident with a coat of primer gray paint! 

I know a guy in the hobby who takes a kit body from the box, no prep at all and squirts hardware store spray paint on it. He puts no effort into his models, and at the same time is upset that he never places in contests.  I try to explain this to him and he wants no part of it!  His solution is that judges should view models from a distance. He thinks the hobby should lower it's standards to his build quality instead of working towards those standards to win an award.  Don't be him!

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I know a guy in the hobby who takes a kit body from the box, no prep at all and squirts hardware store spray paint on it. He puts no effort into his models, and at the same time is upset that he never places in contests.  I try to explain this to him and he wants no part of it!  His solution is that judges should view models from a distance. He thinks the hobby should lower it's standards to his build quality instead of working towards those standards to win an award.  Don't be him!

ha!  I think there's one in every group....or forum. 

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I always use a coat of primer on every model. No matter how well I think I've done my bodywork I always seem to find a mold line or something that I just didn't see. I would rather catch it when it is in fast drying primer and easy to fix than when I put a color coat down.

Here's your answer, plain and simple.

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I've learned to prime everything myself...I prime not only the body, but every little piece (save for plated pieces). There are several reasons I've decided to do so, but the main ones are as oldcarfan said, it helps identify lines you may have missed or flaws you still need to address, and the other is because it makes the paint coat stick better (that's part of what Primer is designed to do). I'm getting better and better and paint, but I'm still new to the hobby and am far from great at it...I haven't even used my brand new airbrush yet. My first few builds I really struggled with the spray paint. I kept putting it on too thick or too wet, ESPECIALLY with color molded bodies. Part of it was I just needed to get a feel for it, as everything I'd ever spray painted in the past was large, metal, and the finish didn't need to be perfect, but another builder on YouTube recommended I try priming my builds, because it helps to keep the paint from running as easily, and also helps you to not have to use as many coats of the more expensive colored paint to get good coverage. It's worked very well for me, and I don't use a high-end primer. I usually get my primer from Oreilly Auto...I use Brite Touch because it's pretty inexpensive for a can and seems to work just as well as anything. Here's the way I've come to look at it; automotive manufactures are always trying to save pennies when manufacturing new cars, but they still use a primer coat at the factory when painting, so obviously it's very important to keeping the paint looking as good as it can long into the future.

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We all have our techniques - it doesn't mean that what others do is or isn't correct. I just describe what works for me.  If we start going by what wins contests then I have taken first place awards at contests with models painted with no primer.  ;)

Snake 45. Pigments are solid (like in a powder form). Pigmented plastic is opaque. But many yellow or red plastics are semi-translucent and I suspect that they use dyes (not pigments) to tint those plastic. .As far as dyes leaching out of plastic, that is not a myth. It has happened to me and to other modelers I know (or read about in the forums). As I see it, the solvents in paint cause the dye leaching.  But those solvents are also mildly destructive to the plastic itself. If you tried to remove all the dye for the plastic using that solvent, the plastic itself would be destroyed.  That is my best explanation.

 

 

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If pigment can leach out of plastic, then there should be some chemical you can soak the plastic in that would leach ALL--or most, or even a visible amount--of it out. Show me that chemical and I'll admit I'm wrong.

Trouble is, the "coloring" used for polystyrene, particularly red, isn't so much a pigment as it is a dye, and as such it can (and often will!) bleed through lighter colored paints.  That was even a problem years ago with the old AMT lacquers--paint white over their red, it turned pink.

Why dyes?  Very simple:  The old colored pigments in the paints we used years ago are, for the most part, no longer permitted in any paints, save for the oil and acrylic paints used in fine artwork.  For decades, many of those colors (anything yellow or red in particular) used heavy metals (such as lead, cadmium and barium)  to give strength and color-fastness to the paint--those have been banned from consumer-market paints for nearly 40 yrs now.  They have been replaced by synthetic dyes that can bleed through lighter colors, particularly succeeding coats of lacquers which have, to at least some degree, solvents that actually penetrate the previous layers (coats) of paint.

Art

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And yet, when I've stripped white paint that's "tinted" pink from a red body, what goes down the drain isn't pink at all, it's pure white.

And the red body is still just as red as it was when it came out of the box.

I simply don't believe color--pigment, dye, or anything else--is leaching out of the plastic and into the paint. I DO believe that some paints simply aren't opaque enough to cover.

 

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And yet, when I've stripped white paint that's "tinted" pink from a red body, what goes down the drain isn't pink at all, it's pure white.

And the red body is still just as red as it was when it came out of the box.

I simply don't believe color--pigment, dye, or anything else--is leaching out of the plastic and into the paint. I DO believe that some paints simply aren't opaque enough to cover.

 

....as long winded and sometimes ridiculous as these forum discussions get at times,,,,I have to agree with Snake on this one. I've built a few in my day,,,maybe a few hundred,,,,maybe  even more, but in all cases of painting, stripping, whatever....I have never seen any color of plastic run, and I mean ever. cars, military, even some odd builds thrown in made by makers world wide, I have yet to see the color seep thru and wash away, even after stripping colored parts with every chemical we all know and love, the colors have never seeped, run, or just got scared and took off.....some primers and paints simply don't cover some combos of colored plastic well, regardless of the skill of the painter/ builder.....its part of the ongoing mystique of everything plastic that  goes together to create a greater model car...lol.......just my 2 cents....the Ace.........:P

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Thanks, Ace. B)

I also think that the wavelength of red light might have something to do with it. You'll note that red is on the far end of the color spectrum, so its wavelength is either the longest or the shortest of all colors (I forget which it is). I think this wavelength might have some advantage in penetrating other colors of paint.

I have no scientific evidence of that, it's just a theory of mine. B)

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Hi all

My approach to primer is somewhat more selective.  Admittedly, this may be due to lower standards on my part. For perspective, I am not building for contests, just for my shelf so I am the only one who has to be satisfied with the final product. I do want things to look as good as possible, but sometimes I just want a quick, pain free build.  I have been doing this for a long time, but still find painting to be somewhat Alchemy (I can do the same thing with the same materials at the same time and still get different outcomes).  I sort of look at each step of painting (sanding, prep, fillers, primer, color coat, clear coat, polish) as an opportunity to make things look either better or worse, and I am not always sure which way it will go ahead of time so if I think can skip a step to get to my desired final product I will.  Here is my general thought process relating to primer:

1. For me primer is absolutely required if I have done any body modifications, particularly if any sort of filler material was used.

2. If the body out of the box is pretty smooth (subjective I know) and a molded in a light color and the only prep was light sanding the edges and washing I prefer to skip the primer if using a paint designed for styrene (eg Tamiya, MM/Testors).  I have never had trouble with these paints sticking to raw plastic and the body lines and details remain more crisp with only the thin coats of top coat and not the relatively thick primer layer. It is one less chance of getting a paint run or piece of dust in the finish. I have also had pretty good luck with the Rustoleum 2x Paint and Primer all in one rattle cans.  I know some folks are not fans of the rattle can hardware store paints, but with multiple quick light coats I have had some pretty good finishes (with a little bit of polishing).

3. Undercarriages mostly get primer since I am never quite sure what I might want to use for fine detailing (if anything).

4. Usually skip the primer on interiors to preserve detail and save some time and number of steps. Also I tend to us a lot of "covering material" on the non-detailed parts of the interior. Floors often flocked or covered with "felt type" paper for carpeting, Seats finished with various tapes, nail polish strips, decals, embroidary floss, etc.  So primer would be a waste on these areas.

Hope this is useful.  It is what is currently working for me, and not intended to suggest there is any "correctness" to it.

 

Theo

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Always prime bodies however; use primer that will complement the final color. 

For instance, Turquoise will pop over flat white.

Gloss black will look good over flat black.

Red over pink primer. 

When I paint a chassis or suspension components I usually don't prime first. The colors used are usually used as primer anyway.

A wise LHS owner once told me to use silver paint over colored styrene to block the inevitable "bleed through" of the molded color.

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