about the origin of yellowing of oils

adridri

Hi.

I Found this paper while doing some research about yellowing of oils, it might be of interest to the forum, for the sake of understanding where this comes from for comonly used oil mediums. It's open access so anyone can download it from the editors.

For non-scientists artists here that don't have university access to research papers, in case you are interested in accessing the cited references (or other research papers that can be found in google scholar) for further reading, you can use the following website https://sci-hub.41610.org/ just paste the title, the doi or the url of an article there and it will give you access.

You can read more about what is Sci-hub here and give a thumb up to Alexandra Elbakyan: https://fr.wikipedia.org/wiki/Sci-Hub

Turns out yellowing is not due to aging but to storage in dark conditions, exposition to light reverses the effect but is not recommended due to other detrimental effects. I would have thought the opposite.

Adrien

MoleMan

@adridri,

Adrien, that is interesting. Haven't considered greatly the apparent difficulties around yellowing/darkening - we could call it discoloration if you like. It makes sense though, that whilst chemically derived pigments can prove themselves to be fugitive regarding maintaining chroma (fading if you like, due to exposure to light) - linseed oil might respond differently.

I don't know, and I can't guess - but potentially, and perhaps, sun-bleached linseed oil might offer a clue. Haven't as yet followed any of the links you provided. but I will, and I think it is a worthy topic and worthy also of perambulation. 

Rgds, Duncan

Abstraction

There are two forms of yellowing. Dark yellowing is the one your article refers to here and it is reversible. This is the one we are likely to notice happen to our paintings as it occurs relatively quickly. A painting shouldn't be put in direct sunlight but only requires to be put into a well-lit room to reverse dark yellowing. If we care about our paintings long-term we should think about lightfastness of pigments. I stopped using Alizarin Crimson for that reason.

Age-related yellowing: However, over time all painting oils yellow permanently with age. I can't find a good source on age-related yellowing quickly but here is a reference at least.

"Age related yellowing of oil binders is, unfortunately, irreversible. Factors that contribute to age-related yellowing are numerous, complex and still a matter of debate among artists and conservators. The artist pigments themselves do not go yellow, but it is interesting to note that lead white pigments increase in transparency with age (There are examples of this in the National Gallery in London- passages of white which have become ghostly). If the pigment becomes more transparent with age, any yellowing of the binder will gradually become more obvious. Titanium White and Zinc White are not known to become more transparent over time, at least I haven’t come across any research which suggests so."

Evie Hatch 15 October 2019 at 12:32 pm in comments section.

https://www.jacksonsart.com/blog/2019/10/04/what-is-dark-yellowing/