MITRA Forum Question Details

​Actually we would LOVE it if someone in the conservation field were to conduct a study to look into concrete numbers regarding paint additives...so I will just leave this statement here for my conservation science colleagues to read (and hopefully someone will become inspired!). The information in our document is based on actual experience with cleaning works of art...both from our own experience and anecdotal evidence provided by other conservators. Every so often we will encounter a painting by an artist who is known to have used clove oil or a painting that lists clove oil on the reverse as an ingredient in the paint. Many of these paintings have proven impossible to safely clean, meaning the yellowed, degraded varnishes used to coat the surface cannot be removed without causing irreversible damage to the paint layer. Clove oil is an attractive additive BECAUSE it hinders drying...but adding too much can create a film that remains sticky and does not form a cohesive, healthy paint film, one that will remain sensitive to even the mildest of solvents. Most likely adding a drop or two to a substantial amount of medium is not the end of the world, but artists often add far more than is necessary in order to combat the drying processes. As with anything that is potentially problematic we simply request that you record your use of any materials/additives on the reverse of your painting so that your work of art can be properly cared for later on down the road. It may be possible in some cases to remove a degraded surface coating from your painting using aqueous methods, for example (should your painting require such a treatment...remember just because you might use a stable varnish does not mean that someone else will refrain from re-varnishing your painting later on down the road), something that a conservator would know to look into if they know that an artist used something like clove oil as a paint additive. 

I would not expect you (or others) to have ​experienced any issues with varnish removal...at least I certainly hope not at this stage! It is far too early in the lifetime of a painting to attempt to remove a varnish unless absolutely necessary. What may be problematic is varnish removal further down the road as I stated above. I suspect that Geneva does not add driers to their paints and probably adds just enough clove oil to create the desired effect (and therefore avoids the creation of unwanted "sticky" fillms)...but without additional testing it is hard to know what kinds of problems may occur during future varnish removal. Again I emphasize that the field of conservation would be well served to look further into such matters...one can find similar claims made by artists who are wetted to Maroger mediums...that they are stable and will withstand the test of time. However we know full well that such paint films remain soluble for many, many years and are sometimes impossible to safely clean (again, the problem of varnish removal comes up). I suspect it is much less of an issue with clove oil but I would still recommend recording the brand and/or material you use on the reverse so that future conservators will know to tread lightly (even though trained conservators ALWAYS read lightly ;) ). 

​We recently heard back from one of our scientists (Dr. Chris Petersen, a retired organic chemist who formerly worked at Dupont). Here is his comment:
"There would be minimal penetration of the vapor if the paint is simply exposed overnight; clove oil is a phenolic type antioxidant with a boiling point >250 deg. Surface penetration is actually what you want if you are tyring to prevent the drying effect that is propogated by oxygen promoted free radicals. The stuff does have a strong odor so even a small amount in the air is overwhelming. As an interesting aside, phenolic antioxidants are used to stabilize acrylic monomers like methyl methacrylate so they can be shipped and stored in bottles. When you add an initiator to make a polymer, the inhibitor is consumed and the free radical reaction occurs."

So in summary there would in fact be some penetration, albeit minimal. Dr. Petersen therefore also believes that this would not drastically impact the "health" of the paints in the immediate future.