In cleaning my studio I found several oil paintings have developed a powdery white substance on the surface. The paintings range in age from two years to three months. I am unsure if it could be mold or an efflorescence due to the location on darker areas made with quinacridone, pthalo and umber. Can efflorescence develop very quickly?Powderypainting.jpeg
Medium is either linseed oil or galkyd and gamsol depending on the piece. The substance easily wipes off, though on the older paintings, it seems to have degraded the surface a bit (surface looks matte and dull). Some of the paintings were stored in a darker space on the floor, some hanging on the wall. None were wrapped. It has been more humid due to lots of rain lately. Other work nearby made with similar materials at similar times shows none of this substance. I have never seen this in more than ten years of painting in this space. I’m wondering if there’s a way to narrow down the cause.
Hello there,
It’s always tricky to tell, so please consider this to be merely one opinion. I’ll be looking forward to reading what others will think and say of this.
That appears to be common oil film ageing wastes.
The oils reticulate with oxygen creating a thermoset polymer, but the chemical reactions do give byproducts, smaller molecules that just stay there or migrate around.
Alkyds and varnishes are no exceptions, smaller bits and molecules eventually come off as they degrade.
That much amount I’m used to see on polyesters put on super alkaline substrates (a rookie mistake), which causes the polymer to be broken down rapidly into such white dust.
So what you show could indicate an unlucky reaction that increased the breaking down of one polymer on the surface of your varnish or painting.
It’s like your surface has been (chemically) sanded: it made it go mat and left the dust behind.
If the painting and colour don’t seem damaged and no colour comes out when you rub a cloth, that’s my bet.
I think Winsor & Newton has a cleaning mixture to help remove these kinds of dust from dry oil painting, but do start with simply a microfibre cloth with soapy lukewarm water to remove that dust. Then you’re good to change the varnish.
If the painting and colour do come off surprisingly easily when you start rubbing your fingers or a wet cloth on it, then it’s a much deeper concern and would be best not to try cleaning but bring to a professional art restorer.
I wish you a nice day,
Lussh
In egg tempera there is a phenomena known as fatty acid migration in which excess and/or not yet polymerized lipids in the paint film migrate to the surface and create a white fuzz, similar to what’s on your painting. It can happen nearly immediately or take years to appear. I have heard a similar efforescence can happen, tho’ less commonly, in oil painting – but I’m not an oil expert, I’ve seen it myself only in egg tempera (my area of expertise). Interestingly, Dr. Joyce Stone (an egg tempera conservator) has commented that fatty acid migration in egg tempera seems to be exacerbated by high humidity, as your paintings experienced. She also thinks it may be supressed by varnishing, which has been my experience. So perhaps if you clean the painting and then varnish it, it would supress the bloom (but if not, then the bloom is under a varnish – more problematic!). I agree with the other commenter: the best course of action would be to take it to a conservator for a diagnosis; if not to repair the painting, at least to understand what happened so it doesn’t occur in the future. A consultation with a conservator can be fairly reasonably priced; one option is to search the data base at https://www.culturalheritage.org/about-conservation/find-a-conservator
We have seen efflorecence develop on a variety of brand’s oil colors over a relatively short period of several months to a couple years. It seems to happen, in our experience, most readily when samples are stored tightly together or are stacked without exposure to light. It wipes off very easily. As Koo mentioned, it is thought that a varnish layer will retard or mitigate the issue.
