Showing posts with label Graphite. Show all posts
Showing posts with label Graphite. Show all posts

Aug 9, 2013

Pills and Pencils

Pills go back thousands of years. They were often squished up bits of plant matter. During the early 1800s, attempts to produce pills with specific chemicals had many problems. Coatings would often fail to dissolve, and the moisture required in pill production could often deactivate ingredients.

In 1843, English artist William Brockedon was facing similar problems with graphite pencils. To get around this, he invented a machine which was able to press graphite powder into a solid lump and produce high-quality drawing tools.

A drug manufacturer saw that the device had potential for other uses, and Brockedon’s invention was soon being used to create the very first powder-based tablets. This technology was adapted to mass manufacturing for medicines. Since then there have been many other ways of produce pills, but the original is still in use.

Aug 2, 2013

Why Number 2 pencils

Pencil makers manufacture No. 1, 2, 2½, 3, and 4 pencils, and sometimes other intermediate numbers. The higher the number, the harder the lead and lighter the markings. Number 1 pencils produce darker markings, which are sometimes preferred by people working in publishing.

The current style of production is profiled after pencils developed in 1794 by Nicolas-Jacques Conté. Before Conté, pencil hardness varied from location to location and maker to maker. Earliest pencils were made by filling a wood shaft with raw graphite.

Conté’s method involved mixing powdered graphite with finely ground clay, shaped into a long cylinder and then baked in an oven. The proportion of clay versus graphite added to a mixture determines the hardness of the lead. Although the method is usually the same, the way companies categorize and label pencils isn't.

Today, many U.S. companies use a numbering system for general-purpose, writing pencils that specifies how hard the lead is. For graphic and artist pencils and for companies outside the U.S., systems use a combination of numbers and letters known as the HB Graphite Scale.

Testing centers prefer Number 2 pencils, because their machines use the electrical conductivity of the lead to read the pencil marks. Early scanning-and-scoring machines couldn't detect marks made by harder pencils, so No. 3 and No. 4 pencils usually resulted in erroneous results and softer pencils like No. 1 smudge. Because of this and general wide acceptance, No. 2 pencils became the industry standard.