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Zinc Oxide: Warnings, Cautions, and Best Practices

14 thoughts on “Zinc Oxide: Warnings, Cautions, and Best Practices”

    • You are very welcome. It can be concerning, we agree, but better to know and have the chance to make informed choices. We are so glad you appreciate the efforts.

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  1. Do you have any plans to test pure titanium white in other binders than linseed oil? Safflower, walnut, poppy or sunflower should have less yellowing as I understand it, although at the expense of a weaker paint film?

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  2. Thanks Sarah wonderful reading., As students it was recommended that lead white be added to any glaze facilitated with zinc to counter embrittlement. I seem to remember Ralph Mayer_ recommending that too in an early edition of his materials and methods.

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  3. I have a tube of Zinc Yellow and I assume it has the same problems as other paints containing Zinc. Is that correct?

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    • Hi Anne –

      Great question. To be honest, my best answer is “not necessarily” as it is made from reacting zinc oxide with potassium dichromate, and I would need to look into this deeper to know if it remained reactive as after formation it has a different chemical structure. Not dissimilar to zinc sulfide, which is stable and can be found as a component in Cadmium Colors as well as in Lithopone (PW5), which we use for our Porcelain White and is considered chemically stable.

      So it will need to be judged separately. I am about to travel so will be out of the office, but can try to look into it some more when I return next week. Or possibly ask on MITRA – a fabulous resource staffed by conservators:

      https://www.artcons.udel.edu/mitra/

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  4. Hi there,
    I wasn’t sure where else to leave this question but decided on putting it where there was “caution” in the title though I know it’s of a different nature. 🙂
    In the past while pregnant I have avoided oil paint altogether. It seems like there is very little accurate information (that I have come by) about pregnancy and painting practices. In the last year I have not used any mineral spirits or thinners though I recently tried the gamblin non toxic safflower based medium. I have also finally introduced gloves to my practice. I am planning another pregnancy but am in the middle of a painting series that I would hate to leave for months. Though I would if it was the safer bet. Do you have any reading materials or recommendations on this? Would a air purifier do anything? Plus I’m reading more about how acrylics aren’t great either and the only problem with oil painting is the spirits or the heavy metals which gloves mostly take care of. Thanks for your amazing article on oiling out. It’s been very helpful!

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    • Hi Robin –

      Thanks for reaching out to us. I passed your question by our Health and Safety Director and he felt you already had a pretty good handle on the topic but also passed along the following points:

      • There is little information available
      • Using solvents during pregnancy is strongly advised against
      • Gloves can help keep the hands clean and prevent oral transfer if you don’t touch your face with your gloves on
      • Good fresh air ventilation is the best way to ensure you’re not breathing in any contaminants. Air purifiers may help if they have the correct filter media and actually filter the air you’re breathing, but unless it’s a “hood” with adequate capture velocity, that’s unlikely.
      • We believe the use of GOLDEN acrylics in moderation during pregnancy with good ventilation and care to not accidently/incidently ingest the paint is permissible.

      We hope this is helpful. And if there is anything else we can do, just ask!

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  5. I am unconvinced by these tests. When I chose a TiO2/ZnO blend white paint, I first decided against lead white because I believed it was impossible to handle it safely. I researched Doerner, Mayer, etc. The argument for a TiO2/ZnO blend in oil is simple: 80% (can vary down to 75%) TiO2 and 20% (can vary up to 25%) ZnO2 is used almost exclusively in all industrial oil based coatings. From my readings it seems tons of research have already been done. There are millions of applications out there with thousands of interior and exterior exposure hours. The two pigments by themselves have issues but in a combination they provide the best solution. TiO2 produces a soft spongy, easily damaged film. Zno2, as everybody knows from the 19th century, produces a brittle film. Both together compensate for each other. I believe both Doerner and Mayer discuss this.
    As a paint maker you know that the industrial coating industry drives the R&D and the product offerings both for pigments and vehicles. And that we painters are of little importance to their choices. If the coating industry can say, with experience of millions of hours of exposure time, that this blend is the best choice then that’s good enough for me.
    (Please note that when you paint on metal, paint failure may have more to do with adhesion than brittleness.)

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    • Hi Eric – Thanks for the comments. You are of course free to remain unconvinced and skeptical, and keep in mind we continue to produce and sell a Titanium-Zinc White, so our position is not one of banning anything but of making sure people are aware of potential risks. And our own research continues in the belief that zinc likely has a role to play at some optimal level of addition. In terms of industrial research, we agree that they were the big drivers in terms of testing, but that field was certainly aware of zinc’s shortcomings and issues from early on, and reading that literature was part of our the background research we did. You might find, in that regard, this overview of some interest:

      Industrial Literature as a Resource in Modern Materials Conservation: Zinc Oxide House Paint as a case Study

      As Dawn Rogala points out, a lot of the issues conservators are currently seeing were first discovered and mentioned in industrial literature, so the findings of the two fields are not really opposed.

      On the issue of Titanium White being soft and spongy, we agree that description fits when using just oil and Tio2 alone, at least in our testing, but there are other ways to combat that without zinc. The main problem with Titanium is that it produces a weak film that is still just marginally flexible enough to accommodate the .5% strain that most oil paintings undergo with changes in humidity and temperature. Especially when compared to the much greater flexibility and strength of lead. See this graph, from our article on using Oils with Acrylic, for some data on that:

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      Also, just the briefest of notes about delamination vs cracking when looking at paint on metal: in our tests all the metal plates were primed, so the failures being shown were always between the paint and a primer, not the metal itself, while non-zinc-bearing paints adhered fine.

      Anyway, we certainly support all artists making their own informed choices, and indeed – as mentioned – we will keep selling a titanium-zinc white for artists to use. Going forward, we will continue to conduct research and share our findings – if not to convince, then at least to help spur discussion and hopefully add to the well of information people can choose from, especially given the dearth of well-documented and published studies.

      Thanks again for chiming in. We truly appreciate the chance to dialog.

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  6. “Because of that, we do not recommend ever using zinc oxide in any material that will be used directly under oils. This would include not simply water-based paints, but any grounds, substrates, or even composite materials where Zinc Oxide might be listed as a component, or where it exists as an anti-corrosion coating, such as found on galvanized metal.”
    Sarah, with reference to JustPaint’s helpful article here: https://justpaint.org/painting-on-dibond/
    In this article it lists four recommended primers based on testing, including Sherwin Williams DTM Bonding Primer. In checking, the EDS data sheet suggests it contains zinc.
    Zinc (as Zn) 2% by weight
    Zinc Compound 3% by weight.
    I assume in dry form the percentage would be higher. The risk is lower within an acrylic dispersion, but your article would suggest that it remains unproven and therefore the risk should be considered.

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    • Hi Brett –

      We saw your question on MITRA and I had a chance to do some further research into the use of Zinc Oxide in commercial primers and paints. As it turns out, in these commercial formulations, zinc oxide is not used as a pigment but rather as an additive to improve mildew resistance (zinc can act as an anti-microbial agent) and to promote stain-blocking (zinc oxide’s reactivity produces cationic ions which chemically interact with anionic stains.) Unfortunately, as an additive, it does not need to be listed in the ingredients, at least within the US. So, while in this instance you found it on an EDS sheet, it could exist in other commercial primers without any mention whatsoever. Given that fact, and its seemingly common use in commercial formulations, it is probably prudent to assume there is some small percentage of zinc oxide in a commercial primer unless a company specifically says otherwise.

      That said, we have not seen any testing on whether zinc oxide bound in acrylic films presents an issue to oil paints applied on top. It is true that we struck a note of caution about this in the article because….well, you don’t know what you don’t know! So until we see some robust testing on this issue, we are left with speculations and best guesses. However, even if one did use one of these primers and it contained a small percentage of zinc, it’s important to recognize that painting on an inflexible solid support presents the absolute least risk. Also, that a couple of coats of an acrylic gesso applied on top might provide an effective barrier between the oils and the primer. But again, don’t know for sure.

      I also want to mention that we are aware that in our article about Painting on Dibond, we do mention the use of oils on top of these primers as being okay. However, that article was written two years before this one on Zinc, so did not have the advantage of this research at the time. Or our understanding that zinc oxide could be included in these types of commercial primers. We will be revisiting that article to see if an addendum is in order.

      Finally, can you share why you feel that you need to use one of these primers? Are you painting on top of Dibond or looking to paint on a metal substrate? Knowing more about your needs could help us provide the best recommendation. And if wanting to play it safe, then sticking to materials made for the fine arts might carry the least risk.

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