If pencils are one of the greatest inventions ever, erasers come in as a close second. Mistakes happen, after all. And the ability to make them go away, to start fresh, and express yourself in a whole new way never gets old!
So wipe out everything you thought you might know about erasers, and read on. Fun facts are followed by a quick tour of how erasers are really made.
Pencil manufacturers make erasers, too, which makes sense since we tend to think that it’s a done deal – an eraser is a regular component of the everyday pencil. But that’s not always been the case….
Pencils with erasers are an American phenomenon. The first patent for attaching an eraser to a pencil was issued in 1858 to Hymen Lipman of Philadelphia. Even to this day, most pencils sold in Europe are eraser-less!
An eraser by any other name? Originally, what we now call an eraser was referred to as a “rubber” because the tree resin it was made of “rubbed out” pencil marks. In Great Britain, they still use the original term. But then they also call trucks lorries, elevators lifts and toilets loo!
An eraser isn’t called eraser by eraser manufacturers, either. Their name for the little erasers on pencil ends: “plugs!”
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.
The pencil plant shown in these photographs makes two tons of eraser plugs for Incense-cedar 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.!
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 three-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 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, which as it turns, 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 that lines up the ferrules and sends them, one by one, down another conveyor line to the machine that eventually places 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!
March 30, 2008 was the 150th Anniversary of the Hymen Lipman patent on eraser tipped pencils.