Re: How are pencil erasers made and what are they made of?

I found a really goood web site that will answer your question about what a 
pencil eraser is made of.  See below:

http://www.virtualschool.edu/mon/Economics/ReadIPencil.html

(Detailed description of how a pencil is made, including ingredients)

The quote below is from the above site.

"Then there's my crowning glory, inelegantly referred to in the trade as 
"the plug," the part man uses to erase the errors he
makes with me. An ingredient called "factice" is what does the erasing. It 
is a rubber-like product made by reacting rape seed
oil from the Dutch East Indies with sulfur chloride. Rubber, contrary to 
the common notion, is only for binding purposes. Then,
too, there are numerous vulcanizing and accelerating agents. The pumice 
comes from Italy; and the pigment which gives "the
plug" its color is cadmium sulfide."


They don't mention how it is made, but I would bet it is either extruded 
(like toothpaste out of a tube that is allowed to dry) and then cut into 
lengths or molded like plastic in a mold.


The following sites show how an eraser works and an other history of the 
pencil.


http://www.newscientist.com/lastword/answers/lwa021.html

(how a pencil eraser works)


http://sul-server-2.stanford.edu/waac/wn/wn10/wn10-1/wn10-106.html

(another history of pencil)

[Editors note: the rubber compound is rather "gooey" when extruded like a long 
rope of toothpaste but is then vulcanized by heat in an oven to produce the 
final tough eraser product,]