MITRA Forum Question Details

This is outside of my knowledge base so I have forwarded the question to a few individuals who are more familiar with acrylic films and issues associated with framing.

Our expert on preservation framing and preventive conservation has asked for some clarification and provided a provisional answer. I have copied his response below.

There are a number of issues, here and much on which I am not sure of. Looking at Duralar, on line, I discover that it is some amalgam of acetate and polyester, whether it is a laminate or co-polymer, I can’t say, and I always thought of polyester by itself, but from what I see on line, I was wrong. It seems that Duralar is used to protect printed paper, but I have no idea as to how it might have been adhered. Now to answer the question

If moisture and “greasy” accretions are found on an acrylic painting that has come from a frame, it is likely that the moisture has come from the mechanics of the frame, namely, the possibility that the glass trapped moisture coming from the wall, but the esource of anything that feels greasy, is harder to pin point. Framing can produce salt on glass and various acids, but oils are most often found when oily plasticizers come from plastics. Among the materials mentioned, in the question, there are three plastics, acrylic, polyester, and acetate. The first, in the paint, and the latter two, in the Duralar and among these, it is probable that the acetate may be the source. As to removal of the Durlar, from the painting, one would need to know how it was affixed, and without a complete understanding of that, leaving it in place is safest, for now. The moisture should evaporate and the greasy accretion may be reduced, with minimal water and a mild detergent. The interior of the frame should be cleaned the same way and everything should be carefully watched, since acrylic paint can soften and cling to glazing sheets, in damp and warm settings. 

Hugh Phibbs

Hi, All. I'd like to make sure we are working from correct product information for Dura-Lar. I don't believe it is a "hybrid" film, co-polymer or laminate; I think it is just polyester. ​From the vendor's site: "Dura-Lar is a polyester based film known for its clarity and stability. It has a high heat tolerance, will not tear or discolor and is archival. Acetate is a general purpose film that is biodegradable, tears easily, does not have a high heat tolerance and is NOT acid free or archival."I believe elsewhere on the site, the vendor claims that Dura-Lar "combines the best of Mylar and Acetate" but I think that is just marketing language intended to persuade artists that the newer product offers the advantages of acetate, not that it is somehow partly acetate.

Also, I believe in this case the Dura-Lar film is the painting support, not a framing material, and the artist is asking about deposits on the clear passages of the film. It had occurred to me that the Primal AC35 application may not have adhered well to the film, and was possibly responsible for the "greasy" residue.

​We recently consulted Prof. Richard Wolbers at the University of Delaware about what may be causing the acrylic to stick in this case and he referred us to an article published in the Studies in Conservation Journal entitled "The influence of temperature and humidity on swelling and surfactant migration in acrylic emulsion paint films" by Ziraldo et al. (2016). Obviously many will not be able to access this article but to sum things up for you it is not really a question of indoor vs. outdoor evironments but really a question of what the temperature and humidity levels are in whatever environment your artwork is being stored or displayed. It tends to be the surfactant that collects on the surface of acrylic films and that can in turn give it the greasy hygroscopic nature that then causes the film to stick it to the glass. For acrylic dispersions that contain non-ionic surfactants one needs to avoid low temperatures (less than 30 deg C) and low RHs (less than 40%) as these surfactants will start to migrate out towards the surface in these conditions. As to what solvent you can use....honestly this is a complex question. You might be better off consulting with a trained conservator on this one as it will definitely require a bit of testing and access to several solvents and/or cleaning formulations that you are not able to readily obtain. Hopefully someone may be able to weigh in with some good suggestions for you beyond the "take it to a conservator" one.