How do you know if you are making good biochar?

Little snippets of ideas have been left here and there, so I wanted to collect a good number of ideas on this.

Here are some factors that I use and have read about:

1. Good biochar is lightweight.

2. It makes a metallic, musical tone when it hits something.

3.  Dust from good char that is dry, can blow away.

4.  When good char is on your hands, mere water can wash it away. If you need soap to clean it off, it's got tars and compounds in it other than carbon.

5. Seeds will germinate in good char.  Not in tarry black mess.

6. Worms will avoid tar char.  They like well-made biochar.  

7. High quality biochar should be able to absorb moisture.

8. High quality biochar will drain quickly.

9.  It will be electrically conductive.  Initial research is examining if that is one way that mycelium can spread so well through it.

Any others you can think of?

John S
PDX OR

10. Good biochar has no smell. Even after it's been inoculated with something stinky, it will revert to no odour.

11. It will crush down easily into small fragments and fines. Incompletely charred pieces will remain intact.

12. If it's re-pyrolysed in a retort at 600C (average wood fire) the mass does not change.

13. If you burn it, the ash left behind is grey, not green or any other weird colour which would indicate metal contaminants like copper or lead.

14. The ash fraction left behind after burning is small, ideally less than 20% if you're using a woody feedstock. Biochar made from crop residues like corn stalks, straw or chaff will have higher ash content, and if you're using manure or sludge the carbon percentage can be well under 50.

Also, as a supplement to #7, good biochar can absorb 3x or more its own weight in water. Try it and see.

Here's another summary from the Dr. TLUD site:

In general, chars with good adsorption capacities have the “feel” of good char:    Properly carbonized wood forms a rigid, easily crushed material that lacks pockets of under-carbonized material. This material differs from the partially burned logs that linger after the campfire goes out. In addition, fully carbonized chars are also not particularly “greasy” to the touch. They are dirty and make copious amounts of black dust, but that dust will wash off one’s hands with just water. If it takes significant amounts of soap to remove the char powder from the pores of the skin, then the char has significant amounts of mobile matter, with the associated concerns discussed previously..  Other tests:  Beyond these simple tests, it becomes difficult to accurately measure char properties outside a proper analytical lab. Attempting proximate and ultimate analyses without the proper analytical equipment is unlikely to yield any insightful results.

John S
PDX OR

A large portion of my feedstock is white pine, despite crushing easily, it is still slightly resinous and will leave robust black stains on my hands.  I haven't made it goal to get it where it doesn't, but I think if I did, I'd give up quite a bit of yield.  So for now, I'll just keep using soap;)