I realise this is a bit of a strange question, but what would bloodstains look like after ~500 years? Specifically, what would a text written on parchment using (human) blood as ink look like after 500 years?
Arterial, venous, and capillary blood all have different colours/characteristics, but is there any likelihood that when used as ink, they'd stay a vibrant red after half a millennium? I assume that blood-ink would go a kind of brownish colour after any length of time after it's dried? I want a manuscript with really crimson-red ink, but would my only options be something like red lead, vermillion, or brazilwood (your standard ingredients for medieval manuscript rubrics)? If blood on its own wouldn't work, is there any way it could be treated so that it stays really bright red?
I've read fantasy stories where there's some kind of creepy old magical text written in blood/made out of people, but to be honest it doesn't seem too far-fetched for reality... I'd just really like to know whether it's possible without magical intervention!
For context, I research late medieval European culture, so while I know a fair bit about manuscripts, I don't know much about blood... I've asked this as a 'hard science' question because I'd really like a citation that I can follow up, but that might take the form of "here's an example of something definitively written in blood, tested by science", or "here's a forensics paper that shows what blood looks like after different lengths of time", rather than the physics-heavy answers that this tag tends to get! I'm struggling to find an answer, because all my searches seem to come up with images of blood droplets in manuscripts, rather than actual literal blood used as ink.
EDIT: I've been alerted to the existence of this question, about what a deep pool of blood would look like after 500 years. While it's definitely interesting, it doesn't answer my question here, especially on the hard-science bit.
I also want to clarify that the parchment I'm talking about is either in a codex (standard book) or roll form, so it's not a single page that would be subject to massive wear-and-tear. Sure, 500 years takes its toll, but there are some amazing medieval manuscripts that survive really well, and they haven't degraded or decomposed.