Don, for myself personally obtaining blood is no problem. As a hunter, I have access to all the deer blood I would want. Also I help butcher some times and as such can have access to cow blood. I suspect that hog blood should be avoided though, and until anyone proves to me otherwise I refuse to use it.
For others though, getting blood may not be so easy and so your suggestion of blood pellets is a good thing. Thanks for the idea. It would also be good as you said for use during a time when fresh blood cannot be had, which is most of the year since we butcher in the late fall or winter. Also most people can't get the blood, because local butcher shops do not slaughter their own animals any more but buy them pre-skinned and ready to carve.
Another thing about blood pellets is that it may significantly reduce the 'nasty factor'. You dont have to gather and separate the blood, which is a big plus, and you dont have to store liquid blood.
It is also possible to freeze the blood serum, and store it that way.
I am still looking for information on pigments, especially natural earth pigments that can well stand up to UV rays. In blood paint on timbers, the main purpose of the pigment is to shield the wood from UV light.
As understand it, dirt is just a fine pigment. The only problem with using regular soil is that it is inconsistent in its color. This may not be a problem for you when you first paint, but later when you have to repaint, or maybe add on and must paint the new to match the old you may have a very hard time finding new dirt to match the old. So for consistency, it is good to 'mine' a pigment from somewhere with a very consistent color to it, which was certainly done in the past, or even better is to produce your own pigment through chemical process. An example of this is the Red Oxide pigment used to paint many old barns in America, which could be simply made by extractive iron oxide from the soil. This substance is very abundant in America (around here, our drinking water is slightly orange before going through the softener because there is so much iron in it)and blocks UV light very well, which explains its popularity as a wood cover. You can also obtain black oxides and yellow oxides from iron-rich deposits. Around here I can simply obtain a deep orange oxide from he ground, especially along creek banks that run near peat bogs.
In other instances, the prevalent paint color used is a result of significant mineral deposits in the area.
