There’s a group I’m designing that believe blood to be sacred, and at 7 they begin keeping it for rituals and such. The amount of blood is about a drop per day and is kept in a (glazed) clay pot that starts out filled halfway with water, there are about 150 of them. It’s kept in a humid slightly below ground room with no sunlight but outside air access. Would they be able to keep this for most of their life, or at least an extended period of time(months to years)?

  • $\begingroup$ Define "Getting Gross". Do you mean you want it to stay fresh and blood like, not get smelly, not get moldy, not ferment? $\endgroup$
    – Nosajimiki
    Mar 23, 2023 at 20:47
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    $\begingroup$ Without magic or a hermetically sealed environment and being frozen - I don't think this is possible. $\endgroup$ Mar 23, 2023 at 20:58
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    $\begingroup$ @TheDemonLord fun linguistic fact "hermetically" derives from "sealed (as if) by magic". Coming from Hermeticism which is a sort of belief system purportedly based on the teachings of the Olympian Hermes. Hermeticism also involved magical practices. Which is where a "hermetic seal" comes from - sealed so tight that hermetic magic must have been used. That has, of course, evolved over time to just mean "very tight" loosing the mystical connotations but it's still amusing $\endgroup$
    – VLAZ
    Mar 23, 2023 at 21:11
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    $\begingroup$ @VLAZ - Where can I subscribe for more fun LInguistic Facts :D (not sarcasm - that was genuinely interesting) $\endgroup$ Mar 23, 2023 at 21:40
  • $\begingroup$ What sort of tech level are they at? Can they distil alcohol for example? $\endgroup$ Mar 23, 2023 at 22:05

5 Answers 5


Antibiotic natural compounds:

Nothing in a low-tech environment will allow blood to be functional for very long at all. If it has to function, you are out of luck. Blood with modern technology can be kept usable for weeks, or months if VERY meticulously preserved. Frozen in glycerol, it can be usable for decades until thawed and deglycerolized.

But if you just want to preserve the qualities of the blood, you might be able to manage that.

First, you need to keep the blood from becoming a place bacteria and fungi like. You can't really heat-sterilize it and you need to keep going into it. But there is some naturally occurring antibacterial compound (something similar to honey, which is full of natural antibiotics) that is added to the blood to kill bacteria.

I doubt you can preserve the cellular structure of the red blood cells, although sugars can help. Blood is commonly kept for transfusions in a dextrose solution to maintain osmotic pressure on the cells. But eventually the blood will likely lyse. You'll have a precipitate of solids and possibly a thin film of lipids on the top, with a deep red hemolyzed liquid layer in between that will largely look like blood (but very dark and possibly clearer than blood).

A very syrupy mix of blood and honey might look like thick blood, stay fluid for a long time, inhibit bacterial growth, with the added advantage that the blood would be sweet when reconstituted (a suitable offering to gods, perhaps?)

Anticoagulants will be essential to keep the blood from clotting into a glop of goo (a scientific term of course). The ones most likely to be useable in nature are ones that affect the clotting cascade (like coumadin, discovered because animals eating contaminated plants bled out) and metal chelators (citrate is a natural weak metal chelator, but the most common one is EDTA, a much stronger one with antibiotic properties, although not natural). A source of heparin-analog ( a strong anticoagulant) could be quite effective and be derived from natural sources.

A far easier way is to dry the blood, then reconstitute it as a red fluid when it is to be used. This is not very satisfying, as the blood stops looking like blood, and the reconstituted fluid would be a bit like red instant milk. But dried blood can be stored for generations, and might be a valuable supplement to the never-reconstituted stuff.



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The clay pot is made airtight by a Symbiotic Culture Of Bacteria and Yeast. Or SCOBY for short. The SCOBYs in your fantasy world are different from the ones that real people use to make tasty Kombucha. They feed on animal matter.

To feed properly on the blood, the culture injects special hormones that stops the blood clotting and keeps its strident red colour. Then it starts slurping.

Or it would, if it wasn't so gosh darn cold. Below 8C the SCOBY clams up and does not slurp. This is good for you, since it means the blood stays preserved.

The Keepers of the Blood are really the SCOBY keepers. They make sure the room stays below 8C but above 5C. Below 5C and the SCOBY does not inject the preserving hormones at all. Below 2C and the SCOBY dies!


by keeping it in their veins. there if they need enough that spilling it on the spot would kill them, they would, as we see from history, kill someone else, if it all needs to be from one person, or if it doesn't, they would have a bunch of people provide a little.

sacred does not mean "we just think it's neat". sacred things are not kept lying around unless you need to have them lying around. and blood doesn't keep that long even with refrigeration. the best way to store blood long term, is inside the animal. just like the best way to preserve meat is to keep it in the pasture till you are ready to eat it.


In the medical world, there are various blood thinners and anticoagulants that will keep blood from clotting up. Mostly inside your veins where that is considered to be a "bad idea". Additionally, there are even more powerful anticoagulants that we sometimes use as pesticides. Don't ever eat any on a dare.

In your world, they don't have pharmaceutical companies most likely, but similar compounds might be found naturally in plants where they'd have the effect of keeping ruminants from eating them.

They use this to keep it liquid. It might not even become viscous.

If the blood is kept in covered containers that minimize airborne fungal spores, it's possible that will reduce or eliminate molds. Bacterial contamination also putrefies, but usually contaminates via contact. So hygiene (washing out glass jars with near-boiling water, etc) can reduce or eliminate that.

And, in a fantasy world, it's even possible that the phytocompound also has antibacterial/antifungal properties too. It's not a stretch at all, there are real-world chemicals like this, and living organisms occasionally adapt to produce them because of their strategic/survival value.



clay pot that starts out filled halfway with water,

This is your biggest obstacle to a useful answer. Anywhere you keep water and a source of nutrients, SOME kind of bacteria or mold can grow. You can add all the anti-biotic mumbo-jumbo you want, but there is nothing you can do to that pot to destroy anything that might try to grow in it that won't also fundamentally destroy the blood.

That said, a single drop of blood will not rot or get moldy or what not if you put it in a clay pot. It dries out pretty quickly leaving a thin powdery film behind. That film will still contain the blood's DNA, Hemoglobin, and pretty much everything chemically speaking that makes blood, blood (other than the water). Dehydrated human blood can last for a very long time without ever "getting gross". The Shroud or Turin for example has been tested to contain human, male, Type AB blood that is from somewhere between 1300 and 3000 years old.

By pouring a single drop of blood into the pot every day, the blood will quickly dehydrate and add its powdery residue to all the other powdery residue, and any decomposers that try to grow in it will die off after it dehydrates. Also, because the blood is being dehydrated, you could keep a relatively small pot for your entire lifetime. If we assume you can live up to about 120 years (minus the 7 for pre-bleeding age), then a pot needs to be able to hold about 41,000 drops. Since blood is about 20% solids, and a ml is about 20 drop, this means that you will need a pot just over 100ml to hold all of the dried blood drops you could ever add to it.

This offers 3 significant advantages over other solutions:

  1. It is very low tech. You literally don't need to do a thing. Just take a clay pot and bleed into it, and you are done.
  2. Unlimited shelf life. While solutions to extend hydrated blood samples may give you months or maybe a few years, this will last for generations. A family cave could contain blood pots going back for hundreds or even 1000s of years.
  3. The blood pot can be very small. This means that if you ever move or get displaced for any reason, it is easy to bring with you.
  • $\begingroup$ "The amount of blood is about a drop per day and is kept in a (glazed) clay pot that starts out filled halfway with water" You'll need a frame challenge if you're ignoring that bit $\endgroup$ Mar 24, 2023 at 16:09
  • $\begingroup$ @TheCommander Edited the question to make that more clear, thanks. $\endgroup$
    – Nosajimiki
    Mar 24, 2023 at 17:42

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