User Manual

Product information
Erasers - Sharpeners
1.3 What is rubber?
Illustration 1: Latex milk extraction
Natural rubber’s raw material, so-called latex milk, is
extracted from a certain tree, known by Indians as the
“caa-o-chu weeping tree”.
The polyisoprene extracted from the tree sap is known as
natural rubber.
Nowadays, grooves are still cut into the trunks of these
rubber-giving trees and the drops of sap are collected in
receptacles.
The process of vulcanisation, i.e. binding molecules together to form a very large molecule
(macromolecule), makes an elastamere out of the sticky, plastic-like raw material and this is
what is commonly known as rubber.
In the meantime, synthetic polymers have been discovered which are similar in composition to
natural rubber.
1.4 Natural rubber erasers
not in the STAEDTLER range
When it comes to the manufacture of natural rubber erasers, the natural rubber raw material
itself serves only as a binding agent and merely makes up around 10 to 20% of the erasers’
composition.
The reason is that although natural rubber is good for removing pencil marks from paper, it
unfortunately also has the disadvantage that it causes smudging.
Additional substances have to be added in order to give the erasers eraser-like qualities. One
such important ingredient is factice, an animal or vegetable-based unsaturated oil such as
rapeseed oil, mixed with e.g. sulphur. As a matter of fact, factice is the real erasing ingredient in
erasers.
Fillers such as pumice or glass powder give erasers their abrasive quality (removal of paper
surface).
 2002 STAEDTLER MARS GmbH & Co. Page 4 of 13
version 07. 2002 subject to change
Note
The STAEDTLER range does not contain a natural rubber eraser
Reason:
Natural rubber erasers age more rapidly and do not perform as well as e.g. Mars
plastic.
Natural rubber erasers contain latex which may cause allergic reactions.