"Why Do" Wednesday - Why Do Pencils Have Numbers?

-
Those school supply lists always call for #2 pencils.  Or when you are filling out those bubble sheets for a test, they also call for a #2 pencil.  They are easy to find in almost any store as #2 is the standard.  But what does that even mean?!


Well, there is a thing called the HB Graphite Grading Scale.  This basically tells you how hard and how black the graphite is.  HB or the #2 is in the middle and is the typical hardness and blackness for most applications.


So the higher the number the harder or blacker it gets.  On the chart above you can see 9H is very hard, but not so dark and a very light shade.  Where as if you go to 9B it is very soft, but also very black and dark.


But why have all these different types of hardness and blackness?  Well for the average pencil user just stick with your beloved #2 or HB pencil, but if you are an artist and like to draw or you just want something lighter or darker you can use some or all of the other varieties. 

#RookieGuru
#GiveMeMore

Comments

Post a Comment

Popular posts from this blog

Flashback Friday - 1869 Transcontinental Railroad Completed

-
Image
On May 10th, 1869, the race to complete the great transcontinental railroad came to an end with a golden spike.  In three long and difficult years, the two companies, Union Pacific and Central Pacific laid nearly 2000 miles of track ultimately meeting in Promontory, Utah. It was known there was a need for this railroad since 1832, but challenges arose in congressional funding and the civil war.  In 1853, congress finally approved funds to survey the land.  However, with the rising tensions from the North and South, progress was slow going.  It wasn't until 1862, one year into the civil war that a Republican-controlled Congress passed the Pacific Railroad Act, which guaranteed public land grants and loans to the Union Pacific and the Central Pacific railroad companies. In 1866, construction finally began, but was not without it challenges.  Terrible weather, long harsh work hours, Indian raids and getting over/through the Sierra Nevada mountains are just a few of the hardship
Read more

Flashback Friday - 1962: 1st US Spacecraft Fly-By Of Another Planet (Venus)

-
Image
On this day December 14th 1962, a US made spacecraft called the Mariner 2 had finally arrived at it's long awaited destination Venus.  The Mariner 2 had launched on August 27th 1962, so it took just a little over 3 months to arrive. Before the Mariner 2 was successful, the Mariner 1 had to be self detonated only 5 mins after takeoff (July 22, 1962) due to it veering off course from a SW glitch.  They were able to correct that issue in the code and use other learnings to make Mariner 2 a success.  Although there were a few hiccups and course corrections through it's flight to Venus, it was able to recover from all of them and hit its mark. The Mariner 2 arrived at Venus on December 14th 1962 and began capturing data with its on-board instruments.  Weighing 40 lbs, here are the instruments it was equipped with: Microwave radiometer Infrared radiometer Three axis fluxgate magnetometer Cosmic ray detector Cosmic dust detector Solar plasma spectrometer Particle detect
Read more

Flashback Friday - 1838 First Public Demonstration Of The Telegraph

-
Image
Today, is an endless vortex of communications.  We have land lines, fax machines, cell phones, texting, Skype, Facetime, satellites and streaming media to name a few.  But it all started with some wire and an idea.  Almost 200 years ago Samuel Morse gave his first public demonstration of the telegraph on January 11th 1838. Source: Wikipedia Samuel Morse invented and patented the Telegraph in 1837.  He came up with the concept and code known as Morse Code to be able to send messages over a wire with electricity.  He encoded the alphabet and numbers with dots and dashes that could then be sent with one telegraph key and received by another. Source: Wikipedia This was the first method of communication that was instantly received on the other side.  Before this invention all communications came by letter or messenger.  On this day in 1838, Morse demonstrated his invention at Speedwell Ironworks close to Morristown NJ.  He sent a message over 2 miles of wire to the amazeme
Read more