Research
spraying white paint (acrylic) on a black or color paint.

A lot of airbrushers seems to accept the bluish fog that appears when you spray white paint over another acrylic paint. What is the reason manufacturers do not make white paint that seems to be white when it falls down on the surface.

It is unacceptable for me, so I have done some research on white pigments which are suitable to make white paint for air brushers. I'm not a chemical expert at all, but there are enough simple tricks to find out what can be done. Follow me on my journey.
The picture above shows some tests I did with white paints. I have sprayed several black spots with Golden Carbon Black which are sprayed over with the white paint. I know there are a lot more brands to try, but I donít want to spend more money for that part of my investigation. Other artists discovered the same bluish side effect with other brands, so that was for me an indication to stop here.

A= Cheap gouache paint for children
B= Badger Air Opaque white 8-02
C= Createx Auto Air Brite White 4201
D= Createx Opaque Airbrush colors
E= Schmincke Aero weiss matt gouache
F= Own mixture of Lead carbonate pigment powder with Golden Airbrush Medium

The tests A upto and including E have a bluish side effect. My own mixture does not have any bluish side effect. I remembered that pot with white Lead Carbonate I bought 16 years ago. When I find out this mixture worked, I knew there must be a way to make really white paint. In spite of my discovery I will never use this mixture at all! White Lead Carbonate is very toxic!!
I found some more white pigments to try. I ordered white titanium dioxide
(not toxic) which is a common pigment used in a lot of white paints. I was disappointed. Test G shows a bluish side effect like all the others.
I asked the reseller if he was sure the titanium dioxide is 100% without additions. He guaranteed me it is because of legally regulations to sell this stuff. The titanium dioxide he sells is a product for making cosmetics. A little bit angry about the results I decided to order all the white pigments I can get including another titanium dioxide.

On my list:
Titanium dioxide pigment
zinc oxide pigment
lithopone pigment
Blanc fixe pigment

In the meantime I did a test with white chalk pigment. I crushed a piece of chalk from one of my children and make it to a fine white powder and mixed it with Golden Airbrush Medium. I was disappointed on this one too. The chalk pigment is transparent, so when it is still wet you donít see anything.
Test H shows wet chalk paint. I sprayed a lot of my mixture in the center of the black spot, but you canít see white because the pigments are transparent.
The next picture H shows the chalk paint when its dry! It took a long time to dry, so this paint is not suitable to use with an airbrush. No bluish side effect by the way.
Is it the black paint?
Some artist say itís the black(underground)paint causing the bluish effect.
Time to do some tests to see if that is true. I used 4 different brands of black and 4 different brands of white. They all gave a bleu effect. I am sure it is not the black paint, everybody knows the same effect occurs when you spray white over a color. The Hansa Pro Color Black (row j) is a really brown black.
The theory that black paint have some blue pigments causing the blue effect did not came out whit this one. See my results below.
Row i = ComArt Photo black
Row j = Hansa Pro Color Black transparant
Row k = Createx Opaque Black (textile)
Row L = Cheap gouache paint for children

colom 1 = Badger Air Opaque white 8-02
colom 2 = Createx Auto Air Brite White 4201
colom 3 = Createx Opaque white textile
colom 4 = white titanium dioxide pigment (not toxic) mixed whit Golden Airbrush Medium
Example M shows the lithopone pigment
mixed with Golden Airbrush Medium.
It flowed easily trough my AB, but you can see a blue effect.
Example Na + Nb shows the Blanc fix pigment mixed with Golden Airbrush Medium. It flowed not at all because of the rough grain of the pigment. As you can see it gifs not a blue effect yet.
Example Q shows the Blanc fix pigment mixed with Golden Airbrush Medium.
I crused the pigment grain a little to make it flow better trough my AB. Suddenly the blue effect shows up.
Example O shows the Zink White pigment mixed with Golden Airbrush Medium. Like the chalk example H the pigment is transparent in a wet condition. Its a little blue.
Example P shows another brand Titanium Dioxide pigment mixed with Golden Airbrush Medium. Like the first brand this paint gifs a blue effect.
Conclusion
My research turns out to be a disaster. I have ordered all white pigments available and tested. All the  pigments gave a color shift accept the chalk and the toxic Lead carbonate. These pigments are not suitable for airbrush. I hope this experiment gives an overview for all those airbrush artists who want to find a solution for the color shifting problem and want to experiment with pigments. I want to say to them donít do it!


Update January 2007
Holbein Aeroflash white E060 has a very light color shift to blue.
On the website from Zsolt Kovacs you can read a very good technical examination about color shift. Check it out!