Why does some white fabric turn brown as it ages?

Oxidation. Like rust on steel.

And you wear suntan lotion which can turn brown on white terry.

I think it’s because of phenolic yellowing, which is the nitrous oxidation of textiles.

Hmm, curious. The concept of being “yellowed with age” is so commonplace—paper, teeth, piano keys (ivory ones), bone, even hair—that I guess I thought it was from the same cause across substances and not something peculiar to textiles.

Of course, those things are all organic, so maybe it’s a similar chemical process.

I do know that with some paper it has to do with the acid content.

Was thinking about this while listening to a podcast that discussed smoking. @Hawaii_Jake has the robe ever been exposed to cigarette smoke? That turns everything a yellowish brown.

@zenvelo No, no cigarette smoke. It turned brown hanging in the closet unused.

Wood is acidic. So a closed closet, especially of if not sealed or painted would speed the discoloring.