black + white = blue

[Jose Manuel]

Hello everyone
I am the author of the portrait of Cameron Diaz sbs, in the hair when painting white over black appeared blue.
I have asked a painter and tells me that the problem is in the painting has long blue component, paint I have used is com-art and illustration.
1 is it true?,
2 I said that the tamiya paint does not have this problem

 

[haasje dutchairbrush]

It's a common phenomena in airbrushing called blue shift. I did a quick explenation on it:

http://www.airbrushforum.org/threads/blue-shift-why-does-my-white-turn-blue.13143/

 

[Jose Manuel]

Thanks for the reply

 

[splasha]

As far as I know, Tamiya is modelling paint [ airplanes, cars and such ] and it has a different pigment base than regular airbrush paints.
people who do t-shirts and fabric say that they never experience "blue shift" and that may be due to the fact they're painting on an absorbant medium like fabric.
This may explain why plastc modellers never have this happen.
It seems to lay down on the surface, keep it's seperate colour and not try and blend into each other.

 

[Jose Manuel]

Thanks for the answer splasha

 

[OzAirbrush]

Another problem aprt from blue shift is black is never a 'true' black, you can also get a white + black = brown effect as well I've found. The white could also have a slight tint as well.

This effect generally happens when you've laid down a base of white then start adding form with the black for shadows and depth. Sometimes if you go too far with the black and you want to bring the white back in it goes 'muddy' and you can get that blue or brown effect.

White is opaque and the general rule with opaques is to work from light to dark just for this reason, if you have to correct something you generally need to go right back to the lightest colour and work your way back out to the darker ones.
When you want to add the finishing highlights you really only want to be adding small spots of white at critical spots to avoid this as well.

If you watch the pro's they will layout their whites as a base and really bring out the highlight areas and they will then very slowly bring in the darker areas and 'preserve the white' as much as they can.

 

[Jose Manuel]

Thanks for the information OzAirbrush.

 

[AndreZA]

That is why I don't use black in my black and white paintings. I use Payne's Grey. It creates a cooler black.

 

[jbuckley421]

I don't have any personal experience with this yet, but I recently read somewhere that you can counter the blue shift by adding a minimal amount of yellow to your white. Like I said, I've not yet attempted this personally, but it might be worth experimenting with.

 

[AndreZA]

Orange not yellow. I just use a bit of flesh instead. It is basically light orange.

 

[Jose Manuel]

thanks for the comments