HB Graphite Grading Scale:
What it is and what it's used for
The HB graphite grading scale is used to determine the hardness and the darkness of pencils. The 'H' in the HB scale stands for hardness. The higher the number next to the 'H', the harder the pencil lead inside is. The hardness is determined by the amount of clay added to the pencil leads during production, the more clay then the harder the pencil. The 'B' in the HB scale stands for blackness. The higher the number next to the 'B', the softer the pencil lead is, making it leave more graphite on the page. Blackness is also determined by the clay content in the lead but instead the blacker the pencil mark is left, the less clay was put in the pencil lead during production. 'F' means that the pencil sharpens to a fine point.
Since the HB scale measures the hardness and blackness of a pencils mark, most institutes and people use it in many ways. For example, in the USA, standard tests are required to be marked with HB pencils (the HB mark on the HB scale). |