Some of my older classics suffer from an issue that it´s not photodegradation, but instead, the glue that was used on some parts as instead turned brown, especially in Classics Mirage, HA Barricade and and Calssics Starscream. I have no idea what is causing this.
Not at the moment. :/ But as far as I can describe it, it´s the glue on certain parts that turns brownish, as if some sort of reaction.
Yes, glues and sealants can discolor due to age or in conjunction with other materials. No, I have not observed the issue with the figures you mentioned, but I have observed it on other, older action figures. Other than dismantling the figure in question and completely removing the glue or sealant, I have no idea what can be done about it.
I'm not any kind of an expert, but the short version of one of the articles I linked to above seems to be that primarily light and heat separately or together can cause discoloration, along with possible contaminants in the original glue batch and the glue interacting with the surfaces (or the component parts of the surfaces) it adheres to. Logic dictates that cheaper glue batches maybe non-archival/acidic, and therefore just their normal aging process with lead them to discolor and/or dry out. But, again, I am by no means an expert.
