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Decimal grade mark in pencil

Previously, it was explained that there is a way to display the pencil lead grade with numbers.

How to display numbers

There is No.2.5 (2½) representing MEDIUM.

If you look at vintage pencils, there are many different ways to mark this intermediate step.

In addition, you can find many strange fractions such as No.2.5, No.2 ⅔, No.2 4/8, etc.

It was a question of displaying the same hardness differently,

The reason was found in Henry Petrowski's book [The Pencil].

The issue of monopoly rights arising from patents

In the end, pencil hardness was expressed as 2.5 using a decimal point, as well as strange fractions such as 2 ½, 2 4/8, 2 5/10.

This is because, if you use fractions as a medicine, it will violate the Patent Act.

Henry Petrowski's [Pencil] p.292

At that time, the competition for pencils was fierce.

The hardness display became complicated because of patent disputes.

A pencil marked with a strange fraction has a hardness of approximately F or MEDIUM.

However, since there is no standard criterion for the hardness of pencils

Each manufacturer may be slightly different.

It's definitely worth trying out the pencil yourself.