Knowledge of pencils

What do you mean by the thickness of a pencil?

In JIS, the reflectance when written under certain conditions is defined as 0.30 ~ 0.47 in HB, otherwise it is good if the upper and lower degree is not reversed respectively BASED on HB. It is said that concentration is high as the reflectance is small because it expresses the difficulty of the reflection. Our HB standards are more stringent than JIS and 0.30-0.38. The first person who thought to represent such a density was to make the core of 14 kinds of thickness in the conte of the France and to call it.