2 different recipes. Brands sell different pigment mixtures under this name, so they won't all look or mix alike. Compare the pigments below; the most common is PBk11 Mars Black.
Who makes it
PBk11 Mars Black2
- PBk11LF I Semi-opaqueSeries 140 ml tube · 60 ml tube* · 225 ml tube · 1000 ml can*About Michael Harding
- Blockx Extra-Fine Oil Colours No. 212173
PBk8 Charcoal Black1
- Old Holland Classic Oil Colours No. A367PBk8LF ISeries A18 ml tube* · 40 ml tube · 60 ml tube* · 125 ml tube · 225 ml tube · 475 ml tin* · 1000 ml tin*About Old Holland
Sizes are the ones each line is sold in; marks a size only some colors come in. Check the store for a particular color.