Quantcast

Painting technique

HomeBuiltAirplanes.com

Help Support HomeBuiltAirplanes.com:

Battson

Well-Known Member
Joined
Jan 30, 2012
Messages
610
Location
New Zealand
Hey all,

So I am looking for some after-the-fact advice on painting technique, I've had a problem with painting yellow. Polytone paint by Polyfibre. The problem is, the colour of finish I get changed depending on the aspect I'm painting. Let me explain:

I start with an even white basecoat under the yellow.
Then spray yellow over the top, number of coats depending on the angle. If it's a part I can lay flat, then it may only take 3 coats to get a good even finish. If it's vertical or a complex shape, I need to use more coats as I can't lay the paint down very glossy or I risk getting a run. I try to match the thickness of paint as best I can, not always possible.
Fabric and metal need different practices and 2 or 3 coats on fabric accepts/absorbs a lot more paint without running than 3 coats over metal.

Problems:
When I see the plane in bright daylight, it all looks even and the same colour. In the lights of the hanger / garage, different parts and panels are clearly different shades/tones of yellow. I am not talking about gloss or shine, the actual colour richnessor brightness is different. I think it's the thickness of paint that does it.

Because the fabric accepts more paint to more quickly, its colour is markedly different in different low-light conditions to fibreglass or aluminium parts when needed more coats of paint - although the net thickness of paint may be the same. Under bright daylight it's harder to notice.

I have noticed if the thickness/richness of white undercoat is different, that shows through no matter how much yellow is painted.

Can anyone with lots of experience shed some light on possible problems with my technique or approach which could have caused this phenomina? Or is this a fact of life with DIY painting?
Even better would be suggestions to reduce the problem, but I am pretty sure it's too late for that now.
 

TFF

Well-Known Member
Joined
Apr 28, 2010
Messages
14,177
Location
Memphis, TN
Yellow is a very hard color to paint. Polytone is not a glossy paint. You can help it, but like dope it is not automotive glossy. When you paint you need to have the part in the same orientation it would be on a plane. rudder up/down, elevator should be horizontal lay flat, and so on. The instructions say it is so so on fiberglass and aluminum sheet matching. It is easy paint to use because it melts in each coat. What you can't do is paint out of one can then open the next and continue painting. If you got 5 gallons to use, you need to mix them all together to average out the tone. It does go on thin so if the fuselage had 5 coats and the stab has 4 it can look different. If you need to do fiberglass or Al, I would get auto paint and have the color matched for those parts.
 

Battson

Well-Known Member
Joined
Jan 30, 2012
Messages
610
Location
New Zealand
I'm ok with the cans I have, as all were batch-made for me then canned in gallons. I do mix them together anyway.

Why is having the parts on the same orientation important? Is that so differences in colour are blended smoothly into each other?
 

Dan Thomas

Well-Known Member
Joined
Sep 17, 2008
Messages
5,655
The Poly Fiber manual says that two coats of white under the yellow, then two coats of yelloe are enough.

They aren't enough. I had to use four coats of that yellow Poly-Tone even with the white underneath, and in a couple of places where the white was a bit thin, the gray aluminum Poly-Spray altered the yellow all the way through those layers.

It's not legal to use lead in paints anymore, and lead was used extensively in yellows. Current pigments just don't do the job well. And since Poly-Tone comes from California, I can imagine that some of those current pigments can't be used there either.

I used DuPont acrylic enamel with flexant as a topcoat on my airplane. Yellow, of course, since any other color is a waste of paint:) And it didn't cover well either. And it cracks. An industrial urethane would have been way better.

Dan
 

TFF

Well-Known Member
Joined
Apr 28, 2010
Messages
14,177
Location
Memphis, TN
It is one of the eye/brain things that the brain can differentiate. The grain of the paint looks different in different orientations. The brain expects it. Get into the fancy auto flip flop or candy paint and just shaking your wrist different and it will look different in that place. Not everyone can see it. I try to get friends to help with this kind of thing and maybe 1 can see it; all the others just want to get done. 99% of the rest of the world cant see it either.
 

Brian Clayton

Well-Known Member
Joined
Dec 7, 2012
Messages
1,042
Location
Ivey, Ga and Centerville,Tn
The demon color yellow...... one of the hardest colors to paint. Even painting walls, it is hard to get to come out right. Every coat comes out a different shade. I am painting the wings and tail on mine yellow latex....very low solids content, translucent even.
 

Battson

Well-Known Member
Joined
Jan 30, 2012
Messages
610
Location
New Zealand
The Poly Fiber manual says that two coats of white under the yellow, then two coats of yelloe are enough....

They aren't enough. I had to use four coats of that yellow Poly-Tone even with the white underneath, and in a couple of places where the white was a bit thin, the gray aluminum Poly-Spray altered the yellow all the way through those layers.

...(abridged)... Yellow, of course, since any other color is a waste of paint:)
Haha - we are definitely using the same paint :) I am just glad we went for 140 Orange Yellow which is a slightly darker orange-er shade.

Sounds like my troubles are Par for the Course.

I did email Polyfibre about this, no reply, I guess they know it as well as we do.
 

Battson

Well-Known Member
Joined
Jan 30, 2012
Messages
610
Location
New Zealand
Still no reply from Polyfiber on this.

I have determined from more experience that the problem is the white undercoat. I needed to add more white to get an equally thick white base on the complicated shapes / vertical parts.

Don't skimp on the base coat, or your yellow/red topcoat will look average in white light, and you can't do anything to fix it... short of a full repaint.

I have to say, overall I am disappointed with Polytone. Mostly it's tendancy to soak up whatever lands on it. From blood of dead bugs, to dye from evaporated drops of fuel, and of course powdered Aluminium-oxide streaks as the plane wears in. Each of these leaves a permanent mark, which requires a minor top-coat stripping job and repaint. Sure the rework is easy, as advertised, but wow do you get a lot of practice... :mad2:
 
Top