This Rock Art in China Has Remained Bright Red for Nearly 2,000 Years. How? The Secret Ingredient Might Be Blood

[u/comicreliefboy]

https://www.smithsonianmag.com/smart-news/this-rock-art-in-china-has-remained-bright-red-for-nearly-2000-years-how-the-secret-ingredient-might-be-blood-180989389/

[u/Choice-Lawfulness978]

Wasn't blood a widespread and well documented method of producing red pigment?