Zinc White

sokolean

I wanted to mix the grays for a waterhouse copy when I came along two tubes of oil paint of zinc white.
One is listed as CL the other is not. I already experienced the same thing with two tubes of titanium white. One
which includes only titanium dioxide being labeled as CL. And by the way is zinc white a toxic paint and if yes in which matter, inhalation or touching. I surfed the internet but I am not getting any clear explanations. Hoping on the knowledge of you guys out there. Greetings, Marc

Mark_Carder

Zinc white is not toxic, they put it in baby rash ointment Desitin. I never tried it because it is the most transparent white of all and I like my paint opaque.

sokolean

Mark, I want to thank you for your fast answer. I guess the tubes have wrong labels then.
Or maybe the put it on there because it is dangerous to aquatic life.

dencal

sokolean

Zinc white has a characteristic of absorbing water from the atmosphere. This can occur on a dry painting surface. As it does so the paint can swell and crack, worse delaminate.

When artists working with oil paints want to add white to their palettes, many turn to paints pigmented with zinc oxide, which is cheaper and less toxic than paints pigmented with lead carbonate. But much to the horror of artists and art conservators, zinc white, unlike lead white, often turns brittle and cracks within just a few years. Stuart G. Croll and Malia Zee of North Dakota State University, working with Marion F. Mecklenburg of the Smithsonian Institution’s Museum Conservation Institute, are trying to understand the physicochemical process that keeps lead white paint tough but makes zinc white paint brittle. “There are huge differences in mechanical properties and solubility between oil paints made with different pigments, which pose problems in art conservation and restoration,” Croll told C&EN. He believes that the key difference lies within the metal soaps that are produced as moisture permeates the paint over time. Some of these soaps, Croll thinks, are liquid-crystalline ionomers—polymers with both neutral and ionic repeating units. In some cases, metals or ions cross-link these polymers, and when there’s an excess of cross-linking, the paint becomes brittle."

http://pubs.acs.org/cen/science/89/8936scic7.html

Denis

Mark_Carder

I have been researching adding a bit of zinc, about 10% to 90% titanium. Ralph Mayer says it adds strength to the paint film over 100% titanium.

sokolean

Is there a good alternative then if you need a transparent white?

AZPainter

I have been using Utrecht White for many years,I guess about 25 or more and never had a problem. It is opaque on of the most neutral whites as far as temperature (warm/cool) and it drys consistent with most other colors. I can use Walnut oil to slow the drying time down if need be. It has a nice creamy texture and brushes wonderfully. I also like that it does not tend to break down into pigments when used with a lot of thinner as I have mixed it with Ivory Black and Transparent Oxide Red (a transparent Burnt Sienna a few times as a wash to stain a canvas on certain paintings. This is not a common wash for me to use though. Utrecht White is Titanium with some Zinc mixed in. I have never had a problem with drying, cracking, yellowing or any of the other problems whites can have. I find it to be extremely stable.

Mark you are correct about Ralph Mayer and basically what he is talking about is Utrecht White. Try it I know you will like it and coming direct from the manufacturer it is quite a bit cheaper to by. I buy six 150ml tubes, as I do most of my colors.

dencal

Mark_Carder said:

I have been researching adding a bit of zinc, about 10% to 90% titanium. Ralph Mayer says it adds strength to the paint film over 100% titanium.

Mark a snip from Amien (they agree with you that yellowing is not of any significance).

Remember that the last time Mayer revised his book was c. 1971. Subsequent editions were revised by others who were not allowed to change a thing. In nearly 30 years, many facts have changed in the paint-making world.

Denis