2 different recipes. Brands sell different pigment mixtures under this name, so they won't all look or mix alike. Compare the pigments below.
Who makes it
PBk6 Lamp Black1
- PBk6LF I Semi-opaqueSeries 140 ml tube · 110 ml tube · 300 ml tube · 1000 ml tin · 4000 ml tinAbout Langridge
PBk7 Carbon Black1
- Maimeri Puro Oil Colours No. 537
Sizes are the ones each line is sold in; marks a size only some colors come in. Check the store for a particular color.