How long does it take a puddle of human blood to dry?

I was watching an (incredibly strange) movie tonight. There’s a scene where someone is stabbed. Later, someone come across the bathroom where the stabbed man apparently dragged himself before dying. There’s a puddle of the dead man’s blood on the edge of the sink, and he uses it to write a message on the mirror.

Maybe twenty minutes minutes (it’s hard to tell, the movie isn’t entirely linear) have elapsed. Does blood stay liquid for that long outside of the human body? It’s not a particularly big or deep puddle, so I’d imagine it would clump up and dry quite quickly.

Are you looking for time to coagulate or to completely dry? Coagulated blood is still very moist, just not runny.

I have mopped up blood about 14 hours after it left the body. It was still more liquid than solid.

I really, really hope this isn’t a “need answer fast,” but it appears you can find anything on the web. Looks like even just a drop will last a lot longer than 20 minutes: http://bloody2.com/exp11.aspx

Mostly how long you have until you can no longer dip your finger in a puddle of blood to write with it, but it turns out that that’s one of those questions where you’re just going to sound like a psychopath asking it.

That’s pretty much what I was looking for, which I failed to find with Google and is now my newest morbid fascination. I’m amazed by how slowly it dries!

And no, I wouldn’t even say I need the answer, let alone fast. Just idle curiosity, I promise.

Aren’t ninjas supposed to know this sort of thing?