Pencils are manufactured in different hardnesses. The term 'hardness' was originally coined as this referred to the pressure that needed to be put on a pencil in order for it to make a mark on paper. Harder pencils needed a harder pressure than soft pencils. Pencil leads are made from a mixture of graphite and clay. The proportion of the graphite to clay determines the hardness of the pencil lead.
Soft pencils are used by artists. They are ideal for shading. Being soft, the pencil can be used to leave a mark on a piece of paper without leaving an indentation. Soft pencils - 2B and upwards (the greater the number the softer the pencil - a 4B is softer than a 2B), can be useful in many rubber stamping projects. Use a soft pencil when measuring cards or placing stamped images. A soft pencil is also ideal for adding shading to an image.
A soft pencil is also useful for transferring images for stamp carving projects.