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The Great Eraser Caper
- Let's face it. Everybody makes mistakes. That's why they put erasers on pencils!But just how do they put erasers on pencils? How are erasers made? And who makes erasers, anyway?
Who Done it? Photo Courtesy of John Watson
Incredible Eraser Factoids!
(You can use these tidbits of knowledge to amaze your friends!)
Factoid #1: A lot of erasers are made by pencils manufacturers! That makes sense, since we think of the eraser as a regular component of the everyday pencil. But pencils didn't always have erasers. The first patent for attaching an eraser to a pencil was issued in 1858 to a man from Philadelphia named Hyman Lipman. And even today in Europe, most pencils are sold without erasers!
Factoid #2: Erasers weren't always called erasers! The item was originally referred to as a "rubber," because the tree resin it was made of "rubbed out" marks made by a pencil. In Great Britain, the eraser is still called a "rubber!"
Factoid #3: To eraser manufacturers, those little erasers on the ends of pencils aren't called "erasers" at all. They call them "plugs!"
Factoid #4: More and more of today's erasers are made from something other than rubber! While some of the "pink" erasers you find on pencils are made from synthetic rubber blended with pumice (a grit that enhances its ability to erase), an increasing number of erasers are made from vinyl. Vinyl is a type of durable, flexible plastic.
How erasers are made:
Today's pencil erasers are made from either a synthetic rubber compound or from vinyl. In either case, the raw material is blended to the proper consistency and is put into a machine called an "extruder." The eraser material is forced through a small hole producing a long ribbon of eraser.
Each ribbon is cut into strands about 3 feet in length. If the eraser is made of synthetic rubber, the strands are placed in a "vulcanizer," which cooks them under pressure to cure the rubber. When cool, the strands are put into a rotary cutter and chopped into bits -- called plugs. (Vinyl eraser strands go straight to the rotary cutter -- vinyl does not need to be vulcanized!)
Rubber eraser plugs must be tumbled to round-off the edges. The tumbler is a big drum that rotates slowly -- and it holds 600 pounds of rubber eraser plugs at a time! Vinyl eraser plugs do not need to be tumbled -- they're ready to insert right from the cutter.
The eraser plugs are placed into a rotating hopper. As it turns, the hopper lines up the plugs one after another, and sends them down a conveyor line to the machine that will place them on the ends of pencils.
Small bands of metal, called "ferrules" are placed into another rotating hopper. This hopper lines up the ferrules and sends them, one by one, down another conveyor line to the machine that will place them on the ends of pencils.
It all comes together!
The ferrules and eraser plugs move along their conveyors to an insertion machine. The inserter is made up of a series of plungers that move in and out. Painted pencils are carried along another conveyor line past the inserter. First, the machine cuts a small recess around the end of the pencil.
Next, a plunger presses a glue-filled ferrule onto the end of each pencil. Then another plunger presses an eraser plug into each ferrule.The pencils move down the line to still another set of plungers that push the erasers firmly into place. When the glue dries, the pencil is complete!Final Factoid: The pencil plant shown in these photographs makes two tons of eraser plugs for Incense-cedari pencils every day! They also make erasers for mechanical pencils, erasers for pens, and erasers you can use by hand. And they make just a small fraction of all the erasers manufactured in the U.S.!
March 30, 2008 was the 150th Anniversary of the Hymen Lipman patent on eraser tipped pencils. Read more here.
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The Great Eraser Caper