Strange paint behavior

One possibility for paint to look thin in some areas and not others is the painter is not spraying parallel to the surface being painted. I have seen some people spray in an arc shape causing the paint to be thin in spots. As for the gloss paint looking dull. This can be caused by a couple of things. First of all it can be caused by moisture in the air or on the subject. For example, I have been working on a kit in the basement. I had taken it out side to do some painting and the temperature difference from basement to outside was about 10 degrees Fahrenheit. This caused a micro-film of moisture, condensation, to form. When I sprayed the paint and let it dry it was dull and kind of hazy. Another cause could be that the primer was not smooth. This is not that big a factor if the surface was prepped well. Finally, if paint rolls away from a certain point it is due to something on the kit. This something could be oil, wax, dust, or a number of other things. I would recommend always washing with warm/hot soapy water before painting a new layer of paint (wash between primer coats, base coats, and final coats) or if the kit has been sitting a long time in open air. Also it is called fish-eye when the paint rolls away from a certain point. I have learned all of this from full-scale automotive painting. I hope some of this helps.

ONE LAST THING, DON’T SPRAY LAQUER PAINT OVER ENAMEL, UNLESS YOU WANT LEATHER!!

Good Luck,
Jason


If you try painting on a HOT day you may find that the paint will do a thing called solvent pop. This is caused by the outer layers drying before the inside layer/s. when the inside layer dries it releases some gas and "pops" its way through the top. This can be very bad and cause you to sand it down and start over.

Hi Paz!

I'd agree with Magnum. I've been modeling for YEARS and it wasn't until a couple of months ago that I experienced that paint "roll-back" for the very first time. I was going to use SnJ metal powder on a Mustang kit. I airbrushed gloss white over the entire plane first. After it had cured for several days I picked it up and noticed the roll-back. I stripped the paint off and thoroughly washed the model before trying it one more time. That seemed to take care of the problem. I concluded that since I didn't wash the model the first time around, it must have been those annoying invisible residues such as release agents, fingerprints, etc which caused it to repel the paint. I now wash every model first before painting it and the problem has not come back. To me, washing the kits seemed silly because often times the plastic seemed so sqeaky clean! But now I do it anyway. If it prevents me from having to strip the paint then it's totally worth it. Good luck and have fun!

Eric

Lacquer Paint over enamel is bad?

I thought clear gloss coats were lacquer, but are they just enamel?

What about acrylic and enamels? Can they be used on top of each other, and mixed about freely?

In my expierence with automotive paint I have found that if you spray Laquer over "air dry" Enamel it krinkles and looks like leather. This is great if you are painting seats or something that is supposed to be leather. This, however, is not good when you are trying to get that perfect mirror finish. To my knowledge most "canned-clear" or Testor's clear is simply enamel. RonUSMC, the question about acrylics being used with enamels, is a good one. I have never used acrylics myself. I could only guess that the two can't be mixed but they can be sprayed over each other, maybe. Again, acrylics are not my forte.

If anyone knows whether or not acrylics can be sprayed over enamels and vise-versa, please let us know?

Jason

Yes. Acrylics CAN be safely sprayed over enamels but NOT vise-versa, or else, problems will eventually occur in time. Rumor has it, that spaying enamels over acrylics has been -more often than not- an invitation for all kinds of interacting factors to come into play, not to mention that this very interaction usually takes place in a rather "chaotic" manner within a frame of time which spans from a couple of hours to a couple of years. Never been there myself, but this is what I've got from other people's experiences, so why not be on the safe side?

As far as strange (or not so strange) paint behaviour is concerned, one might also want to check and download the following .pdf files:

http://www.sherwin-automotive.com/reference/troubleshooting_guide/sw_tsg.pdf
http://www.transtarautotech.com/PDF%20files/paintdefectguide.pdf

Even though these are troubleshooting guides for painting and/or refinishing REAL cars, they have been an excellent source of information for me on the subject. After all, replicating the real thing in scale is what our hobby is all about, ain't it?

Furthermore, they cover almost every possible case of trouble one might come across while painting, plus they're accompanied with example pictures, and -last but not least- they do analyze the nature of each and every problem, providing the most suitable solution as well.

I hope I've helped...

There is a lot of good information and ideas showing up here, Thanks to everyone for the help. Does anyone know why gloss paint will sometimes have dull spots?
Paz

It happened to me dull spots on gloss paint, I solved the problem by decreasing the distance between the nozzle and the model. And only spray a very very thin layer at the time. It takes some practice but the result is fine.

I put my models in Amonia before I spray them.
Don't do this after spraying a layer, Tamiya Acrylic will come off in Amonia.
There will be no more greas or dirt on the model.

http://users.skynet.be/mbie

Regards

Eric

The problem is the paint was not mixed completely. Spray cans are under pressure and it causes the paint to settle to the bottom with the thinner on top. If not properly shaken and mixed you will get un mixed paint along with just thinner. That is what causes the flat spots as well as the paint not sticking to some areas. This is one discussion our class had at ERAI so the instructor assigned us the task of finding out why. After several days of testing it was the most logical solution. And who said I didn't learn any thing in collage?

Is it possible that there could be a spot in the plastic that absorbed mold release or some other chemical that you just can't get rid of?

I have a car body that I have tried to paint several times and each time at the same two spots the paint wrinkles. Primer to be exact. I've never gotten past that stage because it does the same thing at the same spots each time.

Sanding, stripping, soaking and cleaning; nothing seems to work. I gave up and bought another kit but I sure would like to know what happened.