I know that vegetable oils are clearly oxidized when the smell becomes rancid, but what are other signs that oils are oxidized?
Since vegetable oils are also widely used on (DIY) hair care and not washed off for multiple days, I was wondering how likely oils will form oxidation reactions with the hair fiber in like 3 - 7 days, especially when the hair is exposed to UV light.
Therefore I was wondering, is it possible to test at home to estimate after how many days a vegetable oil will (photo)oxidize on a fiber surface?
The experimental plan I had in mind is to apply a bit of oil on a white cotton cloth (or wool) and let it expose to the sun (UV rays) for a few days. If the oil stain is no longer possible to remove, then some oxidation reaction might have occurred with the fiber.
Does this plan sound fair, or do you have better suggestions for simple visual oil oxidation tests?