To make a pencil lead, graphite is mixed with fine clay – the soft that is used in the finest porcelain and bone china. The two ingredients are combined in different proportions to produce leads of different blackness and hardness.
The most widely used type of pencil is the HB (hard and black). Softer and blacker pencils (B and BB) have more graphite, and harder ones – graded from H (hard) to 10H – have progressively more clay.
The leads for coloured pencils or crayons contain no graphite at all. They are made from pure clay and wax, coloured with pigments.
Picture Credit : Google
