Paint has thickness
Scott Chastain said:
Dear Listers: I would like to know specifically how the pros are able to eliminate the seams between colors and patterns; that is, after the clear coat is applied and buffed, running a hand over the painted surface reveals no noticable transition between the colors. Scott Chastain
RV-8 N898W Paint Merced, CA
Scott no paint expert but when you put paint on top of another coat it builds thickness. Transitions or stripes, you'll have a ridge, as far as I know. The only solution or mitigation is make the paint layer on top as thin as possible. Some colors have greater build thickness than others. I recall red and yellow are thicker because they need more coats to build the color. So plan to put the thinner color on top. Some hot rod guys put their trim/stripes/flames on first, tape off and shoot the base coat on top, a reverse ridge if you will. It is suppose to be better, less noticeable but more work taping off.
I'm sure you will get a better answer (I hope).
One trick that does come to mind is
pin striping on transition lines. The hot rod guys do than around their flames and trim, thin width, dark color. It fills in the ridge and than they clear over it all. Putting on more clear coats may help. More clear coats is a needed step if you plan on color sanding. Never did it but seen it done. It's extra work for sure. More clear is extra weight and chance for runs and sags. Frankly ridges are not that bad; you can feel them but visually not an issue.
The clear coat by the way is also made to not NEED sanding either. Color sanding is a technique to get higher shine, smoothness and deeper color.
Color sanding involves several sanding steps using super fine sand paper starting with at least 800 or finer and than going to 1500, 2000....4000 grit. Soapy water keeps the paper from clogging. It smooths minor imperfections, orange peal and any small minute particles or dust in the clear. After careful sanding (in many small steps up to 4000 grit) you buff the clear out. Some times you sand than add more clear coats, than sand again and than buff. If you do re-clear on a smooth surface, runs and sags are more likely. It's lots of work. When painters plan color sanding, they typically add several extra clear coats like 6 verses 3. That's extra weight by the way. More coats means runs and sags are more likely.
Sanding through the clear into the paint would be bad. Ironically if you see color on your sand paper, when color sanding, you went too far. To fix it would not be fun. You basically have to sand all the clear off that panel and repaint it and re-clear and......
You can sand the
base coat, if there are imperfections to remove. Usually you have to repaint the panel again before clear coating. Check with the paint manufacture. I have heard of sanding the base as a matter of course, but most paint systems are made to shoot the base with no wet sanding before clear coating. If the base coats are rough, you may not have put enough reducer in.
Can you imagine Toyota or Honda having to wet sand the millions of cars they make? The key is to put clean, smooth, base and clear coats down, with out dirt, orange peal, runs and sags so sanding is not needed (easier said than done).
Personally I would not want to color sand a whole plane, with the uneven surfaces, rivets and so on. Its 4 or 5 sanding steps and buffing. Not all painters are gung-ho for this technique, but if done right, it can make the paint/clear noticeably smoother (for a perfectionist at a car show). Think about the work!
It's an good technique to correct small amount of localized orange peal or remove dust particles, but the whole plane? Like I said, hope you get a better answer. I am going with JetGlo, single stage and no trim and no sanding!