Automotive Forums .com Car Chat > Automotive Art > Car Modeling > Paint too thick? Pressure too high? Paint Issue
Sixx
12-01-2008, 06:30 PM
I'm currently painting a Henry J Gasser & seem to be having some problems both with masking and slightly wrinkled paint on the roof.
I'm using HOK pre-mixed paint that I've further reduced with RU311, I shot the body and doors on 15 psi with an Iwata CR brush.
The doors came out great but there seems to be some wrinkling on the roof. Assuming that the paint was thinned enough to lay down so well on the doors, I'm wondering if it's more of a "holding the brush to close to the roof" a distance factor. I've done this before where some parts looked great on car and some parts wrinkled. Is there a certain distance for shooting? and does it vary with paints type? Metallics? Pearls?
Also, this is a two tone paint job and I taped the stripes off with Tamiya tape, took the advice of another AF members thread whereby he used a shot of Tamiya clear to seal the edges of the tape before he sprayed. After I pulled the tape off, two things happened
the tape left very hard lines (edge) between the 2 colors
they aren't as clear as I've seen done by other modelerscan I successfully knock this edge down without comprimising the pearl color and what steps can I take to ensure a very clean seperator line between colors?
Lastly, I've tried many different primers including Cobra Colors, Tamiya and currently I'm using Plasticote (from the can not decanted)
After sanding mold line with 400, 600 & sometimes 800, I wash the car, dry it well, shoot it with Plasticote, sand it, wash it, then Tamiya white. It seems to work well as I check the car for mold lines, then when I spray the car, ghost mold lines appear. :banghead:
I've read many posiitve things about Duplicolor in Scale Auto, does it seem to be a prepping issue, a primer issue, decanting vs. spray can problem?
Sixx
12-01-2008, 06:33 PM
http://i37.photobucket.com/albums/e79/designsbydercock/aqe3.jpg
http://i37.photobucket.com/albums/e79/designsbydercock/AQE.jpg
I meant to send these pictures to serve as examples
taliesen
12-01-2008, 08:31 PM
From the pic of the roof, I'd say you're too close, and also spraying from a bad angle - looks like the paint is being moved away from the a pillar. Try being more perpendicular (90 degrees) to the surface you are painting. If the paint is still wet enough to move like that after it's on the surface, it may also be due to it being not thin enough, or you're using too thick of a coat at one time.
For the tape - what width were you using? I've heard that the widest size (40mm, I believe) is thicker than the others and can cause issues, but I don't have any to compare with. The other issue could be laying down too thick of a coat with the second color. I don't think you can sand back the pearl coat without ruining the effect, though - my guess is it would be like sanding metallic paint.
rsxse240
12-01-2008, 10:56 PM
I actually had this same issue as well as many others with HOK paints (the walmart kind, not the actual House of Kolor brand). I contacted the manufacturer, Valspar, and had quite a lengthy conversation. They were VERY helpful. The thing with the paint looking like it's "floating away" like the roof of your car is caused by to much paint to fast. Even if you spray in light coats, this kind of paint REQUIRES no less than 30 minutes between coats to allow time for each layer to get an initial cure. This paint uses a really cool (slow evaporating) base thinner, and is exaggerated when the paint is thinned.
It will take about 5 thin coats before you get a decent color coat. So you'll need a really good base coat to start with. Don't use any kind of enamel or acrylic paint for a base.
On a side note, to get that paint off of your model, a good LONG soak in some 90% isopropyl alcohol.
360spider
12-02-2008, 08:17 AM
Paint film is way too thick or subsequent coats applied before previous coats' dry.
ZoomZoomMX-5
12-02-2008, 10:17 AM
That looks more like it's damaged the plastic underneath the paint. Heavy coat of paint and crazed plastic underneath will look just like that. I guarantee if you stripped the paint off the surface of the plastic will look just like the roof.
Sixx
12-02-2008, 06:27 PM
I appreciate the honest feedback, I'm gonna strip her down and re-start again with the suggestions given.
What about the best way to deal with stubborn mold lines! I'd really appreciate some feedback on how to deal with them.
I know Revell has a new type of plastic, has anyone else had any problems with ghost mold lines??? It seems only recently they've been a issue when I build a Revell kit.
rsxse240
12-02-2008, 06:31 PM
The mold lines in revell's plastic can only be removed by sanding them down, then spray primer, sand it down until you just see bare plastic showing through the primer, then hit it with some more primer, sand and repeat until the line is gone in the primer coat. You'll probably have to perform this same method on the rest of the car as well if it did etch the plastic like Zoom-Zoom said.
ZoomZoomMX-5
12-02-2008, 06:44 PM
If you are using paint that's going to craze plastic and/or cause mold lines to continually ghost, you have to use a sealer. You don't want all that to show up again after a good wet clearcoat.
There are many options for a sealer. Some people have great results spraying a good coat of Future on the plastic before primer.
Airbrushing decanted Zinsser BIN shellac-based primer/sealer in between primer coats will work (primer on plastic, sealer, then more primer, then color). MCW makes a great sealer (prime, seal, prime, color).
Sometimes primer itself is just not enough to ward off damaging the plastic from the volatiles in the color paint that cause crazing and ghosting of the mold lines and bodywork. A sealer is a lifesaver.
Sixx
12-02-2008, 08:56 PM
Hey Zoom! thanks for that! I've recently read about Zinnser in Scale Auto but the article never covered mold lines, it mostly talked about covering colored plastic, sealing it from bleeding through.
I never thought about using it for the mold lines.
If I used Future as a sealer, would I thin it to shoot from the airbrush and with what?
Also, would I be able to use Laquers and Urethanes once the prepping of Prime, seal, prime color process?
Awesome advice Zoom and thanks for saving me the frustration of continued mold lines!
ZoomZoomMX-5
12-02-2008, 11:44 PM
Hey Zoom! thanks for that! I've recently read about Zinnser in Scale Auto but the article never covered mold lines, it mostly talked about covering colored plastic, sealing it from bleeding through.
I never thought about using it for the mold lines.
If I used Future as a sealer, would I thin it to shoot from the airbrush and with what?
Also, would I be able to use Laquers and Urethanes once the prepping of Prime, seal, prime color process?
Awesome advice Zoom and thanks for saving me the frustration of continued mold lines!
The article did mention mold lines but generalized as "ghosting", the photos showed color bleed on a hood (a red Miata hood from my collection of Revell Miatas). When you sand mold lines you make the plastic susceptible to ghosting when using hot paint like lacquers and some primers.
The sealer should work fine for lacquers and urethane.
Future is plenty thin as it is for shooting through the airbrush. If anything it could stand to be thicker. It shoots very thin and wet. Practice with it first.
Sixx
12-03-2008, 08:17 PM
Thanks for the clarification Zoom! I went and picked up some BIN sealer and I didn't know what to thin it with since it is shellac based. I shot it straight from the can on a junk body and It laid down way too thick and gritty.
Thanks Zoom
935k3
12-03-2008, 08:26 PM
Shellacs are normally thinned with Alcohol, I would try that before anything else. If you use Future it is very thin and should not need any thinning. It is Ammonia based and can be easily stripped with Ammonia if necessary. It seems to be stable under all types of paint. I use it for clearcoating my decalled cars.
CFarias
12-03-2008, 11:23 PM
I started using the Dupli-Color Paint Shop line of primer about a year ago and have had no ghosting since. The primer is the 1qt can of gray primer, product number BSP100, and non-sanding prime sealer, product number BQ901. They are about $20 each but will last a really long time in the can.
Thin the primer with acetone around 4 to 1 and spray with a high flow nozzle at about 25 psi. After each coat of primer has dried in the dehumidifier set to 135 degF for about an hour I wet sand with 1000 grit automotive grade sand paper to get any nibs or dust out, then repeat until I'm satisfied with the coverage.
The sealer goes on next. I use the exact same procedure for this but I go a little heavier on the coats. The sealer is a very dark gray but white paint sprayed directly onto it still looks brilliant with just two coats or so. It is also a bit tacky, especially when it comes out of the dehumdifier, but will not leave fingerprints and will loose its stickyness when it is wet sanded.
On top of that I've sprayed on automotive grade paints and two-part clears thinned again at least 4 to 1 and at 25 psi and still have not had any problems.
The paints I also thin 4 to 1 with acetone and spray at 25 psi, just like the primer and sealer, but this is best left to your own preferences.
At this point I'd like to say that it is important to wet sand at every stage, even when you paint the clear coat paints. I've painted on colors expecting to polish the clear I'd put on top but the paint underneath still has the look of orange peel if not the texture. Sanding down the clear coat paint is also important. Ofcourse, this can be ignored if you are using a one-shot paint that will be glossy all by itself.
After one shot of clear, cured in the humdifier for at least one hour I wet sand to get rid of nibs and dust, just like before.
Decals can go on next followed by at least two coats of clear. This is again wet sanded until the edges of the decals can no longer by distinguished. Then at least one more coat of clear which will then be polished.
This sounds like a lot of coats but these go on so thin and cover so well that several coats of primer, sealer, paint, and clear are still thinner than a coat of paint from a spray can. But, you arms will get tired from all the wet sanding! Still care must be taken not to load up engraved details with too much paint.
I have used this on plastics from Revell, Tamiya, AMT, MPC, Ertl, Fujimi, Aoshima, and resin and have no problems. Even the clear, thinned with so much acetone has not affected decals though I will be a bit cautious with the first top coat. This system works well for me and I hope it will help others having similar issues.
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