Under colour information

[Stretch]

G'day Folks,

I've been wondering for a while if anyone here knows about painting colours under a top coat to get a slightly different effect.

For example, there's a Top Gear episode where the latest Disco Volante was introduced and Clarkson says they spray the body in gold first to get a deeper red.

Another example is renaissance painters (oil on canvas) used a green for an under colour to get faces to glow.

Is there a handy list on the interweb showing what can be done or achieved?

[Stretch]

Now I don't care what you dress like or what you wear
But please make sure baby, you've got some colours in there

[jmk]

That is commonly done on cars.

Toyota had grey and white primer surfacers to go under different colors. They would use the white primer under solid red and solid white cars. They used white instead of grey because of hiding issues with the solid red. Red pigments don't hide well, so having white instead of grey helped make the coating look more uniform.

The most common is when you have a pearlescent color. Take Toyota color code 051 for example. The white base was actually the white primer surfacer mentioned above. The base coat was then a clear with effect micas on it. The normal clear coat was sprayed above that. By changing the color of the primer, you would get radically different affects.

[Stretch]

Thanks jmk - I can't find a resource that shows what can be expected though...

...where can I learn more?

[Stretch]

This is all I have so far

How do undercoats effect the final color? (painting)

Vermeer's Painting Technique: Glazing

How to Choose Underpaint Colors for Oil Paintings | eHow

Underpainting seems to be the term of choice in the art world

[jmk]

Stretch,

You have found some good sources. Also being in Holland, you should look at Vermeer's paintings (and other Dutch masters). Their painting technique was unbelievably complex. The painting looks radically different close up then when you look at the whole picture. Rembrandt seems to be the most complex. Go to the nearest museum and get as close as they would allow you (in the Cleveland Museum of Art, they do let you get very close) and notice the complex structure of the these paintings.

Then I would do what these articles suggest. Experiment and observe. That is how I learned. Looking at tens of thousands of test panels over the years is what worked. I never had a textbook to turn to learn how this works.

[Stretch]

Originally Posted by jmk

... Experiment and observe. That is how I learned. Looking at tens of thousands of test panels over the years is what worked. I never had a textbook to turn to learn how this works.

I feel an experiment coming on!

I've got a nice big bit of sheet metal in the garage. Time to get friendly with the local paint shop again.

I have a tin of the top coat I want to apply that is about 3 years old. It is 1K Standox - I'm hoping the colour pigments don't mutate with time...

[jmk]

Usually not.

Herberts was the best, at least before DuPont took them over. DuPont's paint was also good.

Have fun.

[Stretch]

...dirty being the word - I had no baby wipes to clean between masking so the finished product is pretty poor. Well who am I kidding - paint finish is atrocious on the test piece but it does give me an idea of the effect of under colour / underpainting and whether it is worth further investigations.

I started with a bit of zincor plate - I half arsed cleaned it a bit with brake cleaner and an old rag...



I then divided the length of the plate into test areas

I didn't clean when I removed the masking tape and so got "some" (= lots!) contamination problems!



From the left

1) I have a metallic top coat black (Mercedes code 199) - no undercoat on that one just sprayed on. It didn't really want to stick. No surprise there.

2) This is a light gray primer

3) This is a white primer

4) This is a red primer

5) This is a cream coloured "filling" primer

6) This is a semi gloss black - no undercoat. This one didn't mind about the lack of a primer and clung on like a good 'un.



I bought the white and the red primer special - but the rest was stuff found in the cellar.


The primers were all MOTIP as was the semi gloss black - the metallic black was DUPLICOLOUR

Here's a picture of the base coat I'd like to repaint my W123 in - Manganese Brown code 480



If it wasn't for the reactions to the muck I left on there I think the coverage would have been about right.

Interestingly the metallic 480 on top of the metallic 199 gives a kind of floating on top of something effect - it kind of hovers...

...the red undercoat definitely makes it look redder - but that's difficult to tell for sure 'cos of all of those spots showing through!

The semi gloss black sample definitely sucks the life out of the metallic brown.

Here's a few pictures of the test piece with clear varnish applied on top of the metallic brown.





I think that the under colour for this metallic paint is a big deal because this brown consists of light and dark paint kind of suspended in itself. The lighter parts of the brown are definitely effected by the undercoat.

I'm now going to make a better investigation - put in a bit of effort this time - and see if I can work out something special.

I'm going to see if red, orange, yellow, gold and silver makes a difference (on the other side of the sheet). I might also look into green...

[Stretch]

Oh yeah and this is a big "up yours" to the monkeys in the paint shop who said "bloody Vermeer what the **** does he know - just spray on a thicker colour coat"...

[Stretch]

...and spoke with a guy who I assume had been mixing paint since the 1970s (when it was a skill rather than just pushing buttons on a computer keyboard). He was very enthusiastic about my little science project and pulled out loads of colour charts. He kind of repeated the information that his colleagues had made earlier on in the week by saying that a thick coat of the top colour coat is eventually going to have an effect. He said I should apply some really thick paint to see where the limits are for the colour coat I want to use.

So I did this =>



This time a bright orange top coat colour was used on top of the light beige filling primer used in the previous investigations.

I applied a really thick streak across the three sections here =>



You can see that the colour is patchy - heavily applied - three thick almost dripping layers - and now there is no under colour effect.


###########


This got me thinking. I'm definitely a DIY paint spraying type of a chap. I have both feet firmly in the "spray it as evenly as you can - wait for it to dry - wet sand it - wait for it to dry - spray over the holes in the colour you've just made - wait for it to dry - wet sand it again - etc - etc" camp so the chances of me being able to apply an even thin layer on top of an other colour is pretty slim at the moment.

For this reason I'm passing the baton on to someone else! I'm not going to go any further with this investigation just at the moment. I will, however, post my plan of attack to try and get some understanding in this "art".

[Stretch]

I did a fair amount of searching about and kept coming back to the colour wheel.

Color wheel - Wikipedia, the free encyclopedia



The colour coat I want to apply is a tertiary colour - brown.

If you look at this link here =>

How to Mix Paint Colors to Make Brown: 9 Steps (with Pictures)

It shows which components of the colour can be used to make brown - on the same site there are five other methods of doing this =>

5 Ways to Make Brown from Primary Colors - wikiHow

So of those methods I determined, by thinning the paint I have, that Manganese Brown 480 is a purple and yellow based brown.


####


Now that I know what has been used to make up the colour I've got I was thinking I could use the information in this article =>

Undertones in Color

To narrow down the likely under colours that would work for the brown I've got.

This guy (sorry I assume a male writer) reckons that all non primary and secondary colours are in effect "grays" - even though they are not gray (if you see what I mean?). So to work out what colour you want to extenuate you need to use the opposite colour of your mix as the under colour.

For my purple and yellow based brown I was going to try a purple under colour and then a yellow under colour to see if this indeed works as this chap says.

A yellow under colour should produce a darker more purple brown

A purple under colour should make a more yellow / gold like brown

I wanted to test this out - I might do so later on - but at the moment I've got better things to be getting on with!

[jmk]

I am glad to see that you are having fun.

Yes, if you make the overcoat thick enough, it will completely hide and eliminate the affect of the undercoat.

If you make your coatings too thick, they will hold up properly. They will crack, and perhaps pop.

[Stretch]

Oh crap yeah because I want to apply thin paint that doesn't crack and fall off perhaps I do need to revisit the under colour phenomenon...

...three (unworkable) super thick coats with heavy runs in them stop the under colour effect for the 480 brown I want to use - that's too much to expect to stay on a car.

[DieselPaul]

Are you going to attempt to spray paint the 123?

I have actually had some success spray painting on cars. My girlfriend has a 190D that needed a fender and a door, so we found a rust o-leum color that matched Mercedes Light Ivory. Sanded the fender and the door, wiped down with pre-paint, primed with an automotive primer, several even coats. Then scuffed the primer with a numerically high sand paper, to get any dirt out and to prep for color. Wiped down, then laid down color, built color slowly, then laid down a final heavier coat. Again, sanded, then used some random outdoor clearcoat I found at Walmart. The finish on both has held up for nearly 3 years at this point. It was a $13 solution that has really worked out. With more effort on my end I think you could probably come up with a really nice spray painted finish.

When I had my 199 Black Pearl / Blue-Black 190E 2.0L painted, the paint was incredibly expensive. My painter primed the car with a black primer to save paint and it worked perfectly. It did not take nearly as long to build color dark enough to match the rest of the car as it would have with a grey primer.