Hello,
Would you mind sharing your knowledge about copper as a surface for an oil painting?
I make artist’s panels for myself and other Seattle artists with aluminum composite material as a substrate. They feature various surfaces.
I’ve been researching copper, and I’ve just learned that, even if it’s sealed properly with Incralac, the copper will only stay shiny for about 5 years, according to a technical expert at Talas. I called to ask about Incralac, and he told me that copper isn’t expected to stay shiny indefinitely, that it’s incredibly prone to corrosion. Because of that conversation, I’ve chosen to stop research and development on copper-veneer panels. I am now reluctant to develop a copper-veneer panel without more assurance from experts that there is a way to preserve its shine that would satisfy artists, conservators, and collectors.
What do you think?
Thanks so much for your time and expertise.
Amanda T.
Seattle
Update: I’m reading the document “Rigid Supports” found in the Resources section, and I intend to study all the relevant documents in the Resources section. I’ve also read previous discussion threads about copper. So I may not need any fresh information, unless someone has something to say about copper on a substrate of aluminum composite material. If I do develop such a panel, my plan is to adhere copper to ACM with Beva 371 film, following the advice of a customer-service rep at Museum Services Corporation. Thanks.
I suppose it’s expected that each commenter signs his or her comment.
Amanda Teicher, Seattle
Just a quick additional comment: it’s not true that copper is “incredibly prone to corrosion.” In fact, copper is incredibly resistent to corrosion, which is why it is so often used for outdoor architectural elements (i.e. rain gutters, roofing, the Statue of Liberty). But, it won’t stay shiny. A layer of cuprous oxide will inevitably form on the surface, which takes it from being shiny and reflective to looking more like an old penny. If subjected to enough moisture, it will form a greenish patina (like the Statue of Liberty), but this is unlikely to happen on copper that is kept indoors.
Unlike oxidation on iron (rust is fragile and tends to flake off), this oxidation layer adheres strongly to the copper and helps to protect it against further corrosion. The only real downside is that you lose the shininess. So I’d be careful about employing copper in such a way that the shiny, new copper surface is critical to the aesthetics of the work. There’s a good chance that will go away eventually, and then there’ won’t be any practical way of getting it back. Historically, copper used as a support for oil painting was primed with white lead, so oxidation at the surface of the copper would not impact the appearance of the painting.
-Ben
Hi Amanda…I have reached out to Dr. Rosie Grayburn on your question as she has had a) extensive experience testing incralac and b) she knows far more about metal chemistry than many of us 🙂 In any case it is good to hear that you have already begun sifting through some of the previous threads on issues (or non-issues) relating to copper. As to the use of incralac and the mounting system you are proposing (copper mounted to ACM) here is what Rosie had to say:
It’s true that like all non-noble metals copper won’t stay shiny forever. Over time, coatings become more porous allowing air/water to reach the metal and cause corrosion, but the better the coating the longer that process will take. Also, Incralac was designed for outdoor use i.e. a much harsher environment. I think Talas’ recommendation for 5-years is based on an outdoor environment. Indoors I believe it would last much, much longer (20 years+). However, If those two metals are in contact, the aluminium will corrode really fast due to sacrificial corrosion but copper will stay ‘safe’ and shiny. That would present a tricky situation…
Dr. Rosie Grayburn
Head Scientist
Winterthur Museum – Scientific Research & Analytical Laboratory
Ben
While what you write is true, it would be misleading to believe that copper used as a painting substrate will not corrode in interior conditions. Every paint sample taken from an oil on copper that I have seen exhibit a blue-green layer of corrosion at the copper interface. This probably is the result of the action of the fatty acids in the oil paint and not specifically the atmosphere. Also, not all copper corrosion products are as benevolent as you suggest. Copper sulfide is relatively stable but chlorides are very problematic and are even called bronze disease. Bronze disease is a self-perpetuating problem and can completely destroy outdoor sculpture.
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