Next time someone suggests not stripping off old paint, "just paint right over the top". Don't believe them.
Do your due diligence and strip old paint and prime your surface.
In the examples below, the painting tape pulled off the new paint. In addition, 4 coats of yellow could not cover the logo and number from the old paint.
Off to go buy isopropyl alcohol and start over.
Replies sorted oldest to newest
Yellow covers nothing. Just about anything you want to be yellow needs to be painted white first. Regardless, I would have taken the lettering off no matter what. The base paint would probably have been ok, but the lettering would have stood out whether it covered or not.
Can't help but think of this movie line...
I agree that yellow is tough, and needs a light undercoat... but I don't think that's your issue. When viewed close up from the side, if the appropriate amount of paint is say 1" thick-for the sake of argument- then the decals are sticking up a foot or more. No color would make them disappear, unless the paint was so thick that all the molded in details would likewise disappear. Decals always have to come off. In fact, where different colors meet, say for pinstripes or where the blue & orange meet the yellow on your shell, these need to be sanded too before a topcoat...or the variances will show through.
Many years ago I worked in a shop that had an in house paint guy. This man was an artist. His routine work was Ferrari, Rolls Royce, the occasional Delahay etc. Demanding work for demanding customers. He was LOATHE to remove all of the paint down to bare metal, (plastic in your case) unless absolutely necessary. The reason...the original paint & primer's adhesion. Sanding to provide a microscopically receptive surface for the new paint was preferable, not as a short cut or money saver...this was the money is no object crowd... and they wanted the best possible outcome.
Also, tape. "Painter's tape" in isle 47 of Home Depot isn't the right product. A quality tape designed for the job won't let you down. Tamiya comes close, the best is from the car restoration world, like Eastwood company & others.
From looking at your first picture, it's clear the paint wasn't able to grab on to anything (no sanding?) and therefore came off in those large chunks.
Just my .02...
Tom
It really depends. This was an over paint from many moons ago:
In the real world, NJDot just overpainted all the former BN cars that came to the shore via the CNJ in the early 70's. I remember clearing seeing the swoosh from the BN under the dark blue paint that was the standard DOT color until it was rebranded NJT. PC and later PRR overpainted their locomotives as evidenced by old paint schemes peaking through as the paint started fading off the upper surfaces.
For models, I do agree that painting over existing paint does need some prep work and removing the paint is the best practice. I just don't always do that myself.
Ron,
I was given an airbrush back in 1981 and could not get the hang of it. I am just a spray can guy. I think if I were painting railcars like you I would have to learn how to use an airbrush. Spray paint out of a can is a little too thick for painting trains. As far as going over numbers, I think you can sand them off with fine paper. For light colors prime with white or gray and you should be okay.
Some years ago (I was out of it for a long time) we used Dawn dishwashing detergent to strip paint off the plastic. Set the shell overnight in a container of Dawn, next morning rinse and let dry.. Never caused any issues with the details,.. so I'm wondering does anyone still use that method for stripping and prep?
Ron,
I have been using a Pasche entry level single action air brush for over 25 years and it does a nice job for painting. It has seen it's share of abuse as I'm not very easy on my tools. Unless you are doing hand lettering, or very fine line work, I think the airbrush is less important than the technique which can only be developed over time. I'm still working on my technique. For me personally, prep work is everything in terms of masking areas down to the tape you use. I use the Tamiya tape as it produces a very crisp edge and folds nicely over details and then use blue painters tape about half way above the modelers tape that to mask the rest of the area. If I need a piece of paper to finish masking, the blue tape holds that in place.
I paint at a distance where the paint nearly lands dry on the surface. It if lands mostly dry you get a "fuzz" effect while if it drops too wet it can run. I'm not afraid to wait and add additional coats as necessary. I don't tend to thin my paints as much as some so I get better coverage. On brass surfaces you typically bake the paint on the train in an oven at 200 degrees F after painting. Haven't tried it on plastic, but it might be worth an experiment?
I should qualify my comments also and say that I have had the best success with solvent based paints as they flow through my airbrush better. While water based paints can used with professional results, I have not learned that technique well yet. I still have close to 300 bottles of Floquil and Scalecoat, but I suspect the colors have shifted in the bottles. Time will tell on the next project.
Have fun and keep at it!
BTW - this is the downside of overpainting which I live with on my F40PH:
1. I should have taken out the original number boards.
2. Note the Home Hardware logo ghosting on the nose. If I have painted this into a VIA rail locomotive, it would have been prototypical. 
Another overpaint done about 4 years after the F40 and I applied fairly thick layer of paint so the original graphics don't show through much at all.
Problem with painting over existing painting is it gets too thick. You'd be surprised at the amount of detail there is on a MTH engine that's almost covered in paint.
I made a gadget to hold my model (boiler, passenger car shell, boxcar shell, etc) out of a length of 4" diameter pvc pipe, capped one end glued shut. Pour however much 91% isopropyl alcohol needed in the tube to cover your model and wait until it's ready to scrape the paint off with a toothbrush. On plastic models I've found there's always a spot or several that the alcohol won't touch and more scraping is required.
I might create a new topic for this, but I'm curious, do any of you use stenciling for renumbering, logos, etc?
Access to this requires an OGR Forum Supporting Membership
