Will Lead White Turn Black when Mixed with Cadmium Colors?

This is a question that has come to us on several occasions, so wanted to take a moment to lay this concern to rest.

Like so many of these often-heard, historical adages, this one has survived because there is some element of truth or logic that it was originally built on. In this case, the concern has its roots in the fact that earlier production of cadmium pigments (Cadmium Sulfides and Cadmium Sulfoselenides) contained some percentage of free sulphur, which could potentially react with basic lead carbonate to form the brownish/blackish compound known as lead sulphide. Along with Cadmiums other pigments that were thought to be of concern included Vermilion (Mercuric Sulfide) and Ultramarine Blue (Sodium Sulfosilicate). In addition, of course, sulphur compounds were a major problem in air pollution during the 19th and well into the 20th centuries, so environmental exposure was yet an additional factor. Ultimately, however, discoloration was almost solely a concern with water-based media and only possibly – and to this day, still mostly anecdotally –  with some oil paintings in the past. Research has simply never born out any clear evidence of lead whites in oil turning black, either from exposure to air or admixture with sulphur-bearing pigments such as the above mentioned, first generation of Cadmiums or the broadly used  Ultramarine Blue. Indeed, it appears that the oil binder itself is a sufficient insulator to prevent these types of interactions.  One can find a summary of this position in Painters’ Methods to Prevent Colour Changes Described in Sixteenth to Early Eighteenth Century Sources on Oil Painting Technique by Margriet van Eikema Hommes, Looking Through Paintings: The Study of Painting Techniques and Materials in Support of Art Historical Research , London, 1998. In that essay the author states:

“When mixed together in a binding medium, certain pigments can cause a chemical reaction that could discolour the paint. Pigments containing sulphur such as vermilion, ultramarine and orpiment can react with pigments consisting of either lead compounds (including lead white and lead tin yellow) or copper compounds (such as verdigris and azurite). However, laboratory tests have shown that in practice these reactions almost always occur in an aqueous binding medium and that the discolorations rarely affect oil paint. In fact, there is also very little evidence of compatibility problems in old oil paintings where less compatible pigments had been mixed. For instance, lead white (which easily reacts with sulphur) was used in combination with vermilion or ultramarine in countless paintings without causing any discoloration. Hence, it is remarkable that the historical texts contain so many warnings about intolerant mixtures….Perhaps the reason for the sources’ caution was the assumption made by the painters that the problems of mixing in an aqueous binding medium would also apply to oil painting.”

This is also echoed in the fairly authoritative entry on Lead White in Artists’ Pigments, A Handbook of Their History and Characteristics, Vol. 2, National Gallery of Art, Ashok Roy, editor, 1993. There the authors Rutherford J.Gettens, Hermann Kuhn, and W. T. Chase state:

“Lead white locked in  drying oil film and protected with varnish endures for centuries without blackening; witness the white collars and cuffs in Dutch portraits. Although lead white is theoretically incompatible with sulfide pigments, and should form  black lead sulfide in contact with them, no glaring examples can be cited. Flesh tones, lead white tinted with red mercuric sulfide (vermilion) especially in oil-medium, have stood for centuries without change; as similarly mixtures with ultramarine in skies and draperies. Lead white mixed with cadmium-sulfide also seems unaffected.” (p.72)

Nearly all the known cases of lead turning black appear restricted to watercolor or fresco where exposure to sulphur is much easier and more common.

If nothing else, we hope the above will calm any concerns about the use of Lead Whites with the full range of colors on one’s palette, including Cadmiums, but if you still have any further questions about any of this, simply let us know.

16 thoughts on “Will Lead White Turn Black when Mixed with Cadmium Colors?

  1. Great post. I’ve only been painting for a year or so and at first avoided using flake white. After using it just once I was immediately impressed at the qualities it imbued; exactly what I needed. Later I learned that lead white takes on a significant role in the maintaining physical structure of a painting. Pasting a passage from Natural Pigments dot com, quoting a Dutch conservationist:

    Dr. Jaap Boon, University of Amsterdam and AMOLF and formerly head of the MolArt Project, offered these important insights into the role of lead white in oil paint film:

    “The role of lead white is multiple. It is a bulk drier that means homogenous drying over the paint film. It reacts with free acids that develop by oxidation of the oil. It links the acids groups of C9 diacids even when they are still acylglycerides thus stabilising the early film (proven by NMR work of Michiel Verhoeven in 2006). At a later stage when the biological ester bonds are gone, it further stabilises the diacids to form a network that is hard to break. And furthermore, it provides a filling material and surfaces for oil-derived compounds to dock.”

    “No lead means that something else has to take over these roles. I don’t think that that magical material has been found yet simply because we only very recently have begun to understand the molecular structure of paints. It is my belief that the period 1950–2000 will bring us many defects in the oil paints that are now maturing. It is time that we develop a molecular level understanding on how to deal with oil paint defects that develop when the network can’t be stabilised with suitable metal cations.”

    • Thank you for the comment! We would also definitely agree with Dr. Jaap Boon’s assessment. We follow his work closely and without a doubt his research is some of the best and most significant being done in this area. On the plus side, Williamsburg has a very secure source for lead and no plans to stop production of it anytime in the future. We have been committed to Lead White as a core and essential part of the painter’s palette from the beginning.

      • Boon does mention that many conservation problems associated with lead white may be due to the wide distribution of particle size such as produced by the dutch stack process
        .
        This paper from MolArt presents some artificially aged samples of cadmium. “The deterioration of cadmium sulphide yellow artists’ pigments” Showing the oxidation of cadmium zinc sulfide can create problems including the creation of brown oxides in the upper layers of a painting.
        Here again the author points out possibility of earlier production methods contributing to the instabilities.

  2. Interesting article. I think people are too quick to cry “chemical interaction.” Very often chemical analysis shows the real problem to be UV light or last century’s manufacturers poor understanding regarding how to produce a color.

    Because Van Gogh used Chrome Yellow (lead chromate) and it darkened after 100 years, people jumped on the lead interaction bandwagon. However, a 2011 chemical anaylsis showed it was exposure to UV light that had changed the compositon of the chromium in the surface layer (a hairwidth layer, and below that, the paint was still a vibrant yellow).

    Today we know Chrome Yellow can be kept from darkening by dipersing it in amorphous scilia. These encapsulated varieties of chrome pigments are stable to light, high temperature, weathering and resistant to sulfur dioxide. But people are so frightened by dated information most won’t use them.

    It’s unfortunate people keep circulating dated information which has been proven false by science and that they don’t realize that genuine flaws, such as those affecting Chrome Yellow, have been completely overcome by 21st scientific production techniques.

    Thanks for the post! Good science makes great art!

  3. Hello Sarah,

    Thanks for the interesting post. Would it make you reluctant to recommend lead white for use in egg tempera painting? I currently work with titanium, but am considering switching to a lead white dispersion

    Koo

    • Hi Koo –

      Apologies that I am a bit late on seeing this comment but in general, outside of the general health concerns around lead, it should be able to be used in egg tempera. However, there is some risk it could turn black if in contact with sulphur-containing pollution, although few examples of this happening exist and so the problem is felt to be rare. That said, what cases of color shifts are documented appear confined to water media, so would still want to proceed with some caution. That said, it certainly was a part of past tempera paintings and clearly many if not most of those have survived.

  4. I’m happy I found this post today. I’ve been telling students that when one uses lead white, we avoid cadmium colors and that’s WHY we use vermilion in admixtures made with the white. To be honest, I’d never heard of the possible interaction with ultramarine blues. Thank you so much for sharing this information. I’ll pass it along to anyone I’ve misled:)

    • Please do pass it along! And apologies that it took us so long to respond……a whole series of emails from the blog site got labeled as spam and we just discovered them today.

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