What is the hardest grade of pencil
Pencil claim to have first used the HB designations, with "H" standing for Hardtmuth, "B" for the company's location of Budějovice, and "F" for Franz Hardtmuth, who was responsible for technological improvements in pencil manufacture. As of 2009, a set of pencils ranging from a very soft, black-marking pencil to a very hard, light-marking pencil usually ranges from softest to hardest as follows: Koh-i-noor offers twenty grades from 10H to 8B for its 1500 series; Mitsubishi Pencil offers twenty-two grades from 10H to 10B for its Hi-uni range; Derwent produces twenty grades from 9H to 9B for its graphic pencils and
Pencil pencil hardness of different coatings. This test defines a "pencil hardness" of a coating as the grade of the hardest pencil that does not permanently mark the coating when pressed firmly against it at a 45 degree angle. For standardized measurements, there are Mohs hardness testing pencils on the market. The majority of pencils made in the US are painted yellow. According to Henry Petroski, this tradition began in 1890 when the L. & C. Hardtmuth Company of Austria-Hungary introduced their Koh-I-Noor brand, named after the famous diamond. It was intended to be the world's best and most expensive pencil,