My point of view in the discussion is that the colors are oxides, and not likely zinc oxides. Iron oxides are not likely to be chemical compounds, but rather chemical reactions. The "discussion" seems to be, can sunlight provide the energy to drive the chemical reaction, to create new oxides on case colored gun surfaces, which results in a different visual appearance.
Earlier, there did not seem to be dispute that hidden, internal gun surfaces, may very well be protected by various traditional and modern oils, probably for corrosion and wear resistance. But, that is a general area of many guns, where case colors do not seem to be affected, or as affected by the appearance of fading.
craig, I think we are haggling over semantics then. Iron oxides would be minerals in anyone else's book and most definitely they are chemical compounds. How can they NOT be chemical compounds? Everything that physically exists is a chemical compound. They are not reactions. They are created by reactions.
But be that as it may, I don't think sunlight fades them. I see no evidence that it does and anyone that does the case colors in the windows test seems to find the same result - no fade.
Do you think sunlight will fade a rust blued barrel? That is another iron oxide.
![[Linked Image from i.imgur.com]](https://i.imgur.com/qclHjMQ.jpg)
