Zinc Oxide – Reviewing the Research

TIT-ZNC
Titanium-Zinc cracks easily (Photo from juspaint.org)

An expected and alarming article about the hazards of using zinc oxide in painting. Research shows that “combinations with a wide number of other pigments, including Titanium White, does not appear to mitigate zinc’s brittleness”, and that “lowering the percentage of zinc to even these levels* did not seem to make the blends any safer to use” (* previously the manufacterer had reduced it to 2%, but further review showed the need to completely removing zinc oxide).

http://www.justpaint.org/zinc-oxide-reviewing-the-research/

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Pure Titanium White Oil Paints

Zinc_White01
Pure zinc oxide oil paints: right out of the tube, Talens Rembrandt Zinc White No 104 at left (ground in safflower oil, noticeable whiter) and Michael Harding’s at right (ground in linseed oil, so, a bit yellowish) – from tubes I bought and, unfortunately, don’t use anymore

A paper published in 2013* raised (even before its publication) a worrisome question about conservation of paintings made with zinc white. It has been demonstrated that paints that contain zinc oxide will become brittle, in relatively short periods of time (as little as three years!). Also, further damage occurs by delamination of adjacent layers of painting made with other pigments. The authors did not mention the amount of zinc oxide in each studied paint, but one can wonder that even small proportions of this compound may cause disastrous effects in an artwork.

The scientists who demonstrated the long term problems with zinc oxide paints also noted an outstanding durability and toughness of the paint films made with lead carbonate. Unfortunately, the health issues associated with lead are, of course, a major factor to avoid its use (I’d be afraid to use it, even with great caution).

After knowing how potencially hazardous zinc oxide can be, I don’t use it anymore. Now, where we have to be careful: zinc oxide is present in several white paints, even if it isn’t clearly stated, as in many “Titanium White” oil paints and even mixed in a few other colors. Zinc oxide (PW4) is blended to titanium white (PW6) in oil paints to give them a less spongy texture. Also, zinc oxide is less opaque, and have a weaker tinting strenght, features that sometimes can be desirable. Recently, I made a list of whites that allegedly don’t contain zinc oxide:

BRANDS THAT OFFER TITANIUM WHITE OIL PAINTS WITH NO ZINC OXIDE (Professional or “Artists” Oil Colors)**

  • BlockX
  • Blue Ridge
  • Daniel Smith
  • Gamblin Artist’s
  • Holbein Artists’ and Holbein Vernét
  • Lukas 1862
  • Maimeri Puro
  • Michael Harding’s (Titanium White No 1)
  • Old Holland
  • Pébéo Huile D’Art
  • Vasari
  • Williamsburg
  • D’Arte Cor (Semi-Profesional)

**Notes:
– This list was made in May 2017, so it may undergo changes or become outdated, if the manufacturer alters the composition, so, I’d recommend to always read the label
– It’s not meant to be a thorough list, just an useful one, as there are some important brands missing (although I’ve checked a lot of them)

*Source: Mecklenburg, Tumosa, Vicenzi (2013). “The Influence of Pigments and Ion Migration on the Durability of Drying Oil and Alkyd Paints” Available online: https://repository.si.edu/bitstream/handle/10088/20490/12.Mecklenburg.SCMC3.Mecklenburg.Web.pdf?sequence=1