For the project I am currently involved in, I may be making a large quantity of blood paint. For those of you who do not know, blood paint is a type of tempera that uses blood serum as the binding agent. Blood serum is the liquid portion of blood with the cells removed, and is historically made by letting blood set outside for a week or so and skimming off the solids that congeal on the surface. It is not accurate to call the serum plasma, because it is more than just the blood plasma. However, with the cells removed it no longer contains the portions prone to disease and rotting.

This blood paint contains a pigment of sorts, which is usually some kind of dirt or other mineral pigment. Often times it will also contain a large amount of linseed oil but not always.

With this mixture, all three portions play an important role. The blood is an extremely durable binder, possibly the most durable binder ever used in paint. It can last for hundreds of years in full exposure to the weather. The pigment is important to preserving the wood also. It serves to block out UV light. Mineral pigments are used because they are stable and unaffected by UV light. The linseed oil (boiled is often used from what I can tell) penetrates the wood and protects it and the paint itself from insect and fungus.

Often times, instead of the oil being in the paint, the wood is first impregnated with linseed oil. Either way, the oil does help the paint to adhere to the wood.

According to tradition, there is a door on a house in Denmark that was painted with a single coat of Ox Blood paint in 1690, and has not been re-coated or repainted since. (Priors Hus, Ærøskøbing)

That is what I do know...

Now, I am in the search for suitable pigments. Historically many different pigments have been used. I know that this type of paint was used in German speaking lands to paint about any exterior exposed wood. However, from region to region the pigment used varies quite a bit. For example, in Zürich the paint is always a deep red, which is not from the blood but from an oxide ocher prominent in the region. However, in Bern the paint is a very dark brown, once again due to local pigments. In Germany, various shades of brown and red are used, with some reds fairly bright. However, it is always the case that a building will be painted the same color as those around it.
In France, it seems the color of the paint varies a lot in a single town (though I am not certain that blood paint was used here)

I am interested in what natural materials I may be able to get from around me here that would yield the desirable colors. I am particularly interested in a dark brown. I am exclusively looking for mineral colors. We have an abundance of peat-rich soil, which is a black-brown. However, I have my doubts as to its stability over time since its color is do to the presence of the peat, which is partially rotted plant matter.

DLB