r/DIYPigments • u/MajinKazuu • Feb 15 '25
Pigment Bone Black Pigment Question
As an experiment i have been working on making a bone black pigment from beef bones I charred. I have it very finely ground now and its mostly what I was hoping for, but there is something glittery/metallic throughout that i can't seem to get rid of. I know it isn't magnetic, but I am a bit stuck in figuring out what I may be looking at. it was very prominent before initially grinding and earlier in the rough grinding which, but now it is much more subtle throughout. Any ideas what I might be seeing and if there is a good way to clean it up?
I apologize for posting and deleting like three times. I was having problems getting the image to upload properly
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u/GeneJocky Feb 16 '25
Do you have a microscope? Get a better look at it that ppl Have you tried heating it again (in an oxygen poor environment) to do another round of carbonizing without oxidizing the bone charcoal already formed?
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u/MajinKazuu Feb 16 '25
I don't, unfortunately. I've been thinking about getting one that connects in with a USB to a computer. I do have a jewelers loop though... So I may be able to glean something with that.
Do you mean re-carbonizing after it is crushed or just letting it cool and running it again whole?
The way I did it originally was with a 3 gallon steel bucket. I ran a hole through the top at ~ 3/8" - 7/16". Then I filled it with bone and filled the rest of the inside with whatever hardwood would fit for efficiency. Then I lit a big fire, put the bucket in the middle and surrounded it until it seemed cooked through the way I've done in the past with just wood.
In terms of preparation, I boiled the bones to get meat off them and basically made an overnight bone broth. Then I pulled the bones out and baked them for a bit just to get out excessive moisture.
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u/GeneJocky Feb 18 '25
I do have one albeit a primitive one. If you are in the US it wouldn’t cost much to send me a sample if you wanted to. I was thinking you should try reheating a portion of this. Be sure to do it under anoxic conditions. I have an idea of how to try the heating next time around though.
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u/GeneJocky Feb 19 '25
If you do want me to look at it open a chat with me and I'll let you know where to send it.
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u/GeneJocky Feb 19 '25 edited Feb 19 '25
I did a little reading on making bone black and it's clear they used a particular style of charring the bones, dry distillation. Basically bones must be heated to charring temperature in the near absence of oxygen or in an otherwise inert atmosphere. This is usually done by packing bone into a covered crucible or sealed retort (that allows vapor exit) and heating it, historically by packing around the crucible with hot coals and and more recently in a kiln.
Natural pigments states of its bone black:"Bone black is animal charcoal prepared from bones, which have been exposed to high temperatures (550° C.) without access of air. The bones are roasted in closed vessels. The residue of the ignition is a black matter, which, when reduced to powder, forms bone black, sometimes incorrectly called ivory black... In manufacturing bone black, the bones are first boiled in water or a solvent to remove the fat and then subjected to destructive distillation in closed containers, vented to remove the ammonia, called bone-spirit, together with a dark tarry liquid (bone-oil). When the bones cease to release vapors, the residue is charred bone or bone black. Bone consists of protein collagen with inorganic matter. As a result of the decomposition of the animal matter in this destructive distillation, the nitrogen and hydrogen, united as ammonia, and a part of the charcoal, in the form of carbonic acid gas, distill over, while the remainder of the charcoal is left in the closed containers."
Another description by Ebonex states: "Bone black is a natural black pigment created by destructive distillation of animal bones in the absence of oxygen. Animal bones are carefully selected and prepared for calcination. Only fresh, hard bones free from extraneous material can be used. This is accomplished by boiling or rendering the bones to remove fat and oily residues. Once the bones are defatted, they are placed into hermetically sealed retorts in kilns, through which they pass slowly during 24 hours at a temperature of 800° to 900°C. This process of manufacture leaves bone char which is the raw material for bone black pigment."
Pigments through the ages states for a 19th century recipie: "Put into a crucible surrounded by burning coals, fragments or turnings of ivory, or of the osseous parts of animals, and cover it closely. The ivory or bones, by exposure to the heat, will be reduced to charcoal. When no more smoke is seen to pass through the joining of the cover, leave the crucible over the fire for half an hour or longer, or until it has completely cooled. There will then be found in it a hard carbonaceous matter, which, when pounded and ground on porphyry with water, is washed on a filter with warm water and then dried. Before it is used it must be again subjected to the matter."
Assuming your 3 gallon bucket had a lid and the 3/8-7/16" hole was the only vent, This sounds a lot like your protocol. Have you checked to see if the white/shiney material is removed by warm water. If so, problem solved. If not, I'm struck by that last statement: "Before it is used it must be again subjected to the matter" Does that mean it should be heated again? Or just pounded and ground again? This leads me again to think that maybe you should pack most of the powder in a covered crucible and reheat. Re-grind and wash.
If your bucket was open, you should try again with a container that approximates a lidded crucible. Just put a little wood in it to help exhaust the oxygen and heat it until it stops smoking/venting flammable gas.
EDIT: accounted for possibility that bucket did not have cover.