eraser
Or the eraser ( . Ugs also eraser , Ratzefummel ) is a particularly formulated rubber , with the pencil - or ink strokes of paper can be removed and other carrier media. A distinction is made between rubber and plastic erasers.
history
From the middle of the 16th century, bread is said to have been used to remove graphite marks . In 1770, the British Edward Nairne discovered that rubber was suitable for removing pencil marks. The British naturalist Joseph Priestley made this observation public in the same year and was therefore long considered the inventor of the eraser.
Manufacturing
Rubber erasers are made from the milky sap (latex) of the rubber tree ( Hevea brasiliensis ) and factice , a white-yellow mass made from vegetable oils. After adding sulfur , the mixture is vulcanized under pressure at around 150 degrees Celsius . The kneadable rubber mass thus becomes an elastic material. In order to intensify its abrasion, quartz powder and fillers such as chalk and dyes are often added to the rubber compound .
Plastic erasers are usually made of plasticized polyvinyl chloride (PVC-P), which becomes elastic when plasticizers are added.
technology
The graphite particles removed by the pencil adhere to paper by adhesion . The adhesive force between graphite and the rubber of the eraser is stronger than that to paper. Therefore, the rubber absorbs the graphite while it is rubbed over paper (lat. Radere : scratch, scrape). The eraser must wear out so that the exposed rubber can absorb new graphite. When the rubber surface is saturated with graphite particles, the particles are distributed on the paper instead of being lifted off.
A ruler should be placed on thin paper parallel to the erasing movement to prevent the paper from rippling and tearing under the eraser. Alternatively, the paper can be stretched with two fingers while erasing.
Inks and ink erasers are mixed with ground, hard materials such as glass, pumice stone or quartz in order to sand away dyes and pigments . The abrasive erasure removes the surface of the paper and can be seen on many papers, especially on guilloche paper. If the dye has penetrated deeply into the paper, holes are easily ground into the paper when it is erased.
When erasing ink drawings , in addition to mechanical grinding , a physico - chemical process also plays a role, in which the ink line is loosened and bleached .
Ink strokes in technical drawings on tracing paper are difficult to erase. They are usually ground with fiberglass erasers or scraped off with razor blades or erasers .
Erasing clay
Radierknete is like plasticine plastically deformable eraser. Moldable rubber is often used to fine character strokes , hatchings or surface coated chalk and graphite layers to remove or lighten. Kneaded eraser erases less, but evenly. It is also used to prepare areas that are heavily saturated with graphite (where a normal eraser would only run the risk of spreading, "smearing" the graphite) for complete erasing.
Electric eraser
The erasing process can be mechanized by setting the eraser body in motion by means of electromagnetically generated rotation or oscillation . This is possible with devices with mains voltage as well as with batteries or accumulators . Eraser inserts in different strengths are available for these devices; The rapid rotation in a limited space enables very precise, fine and at the same time complete erasing.
Erasers being toys
In the United States , since the spring of 2011, it has once again become fashionable to collect erasers in animal and other shapes, especially among school children. The trend originates from Japan, where the corresponding erasers were brought onto the market earlier and from where the corresponding products were distributed all over the world.
See also
