The graphite in a pencil may vary from soft to hard depending on the mix of graphite, clay and other ingredients. There are various scales that are used to describe the hardness of the graphite..
The HB grading scale is used in the United Kingdom.
Designation
Indicates
H to 9H ("hard")
increasing hardness
F ("fine")
HB
B to 9B ("black")
increasingly soft with more graphite, giving darker marks
In the United States pencils are designated by a number.
Numbered
HB Grade
Description
#1
B
softest
#2
HB
#2 1/2
F
#3
H
#4
2H
hardest
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