Classification of erasers
There are several kinds of rubber erasers:
1. The erasers with a low content of the abrasive substances and with large content of the substances making eraser material more elastic. These erasers are intended for fast and qualitative erasure of graphite traces. During erasure graphite sticks to a eraser which at the same time clears itself because of its rubbing a surface. As a result an erasing surface of such an eraser is constantly renewed. If the eraser is sorted out correctly to a type of paper and graphite so the working surface remains with minimal damages or no ones at all.
2. The erasers with fewer content of the softening substances and with a low content of the abrasive substances, such as pumice or sandpaper, and a big percentage of the other substances and dyes. These erasers are for regular use.
3. The firm erasers with a high content of the abrasive substances. As the abrasives the sandpaper or pumice (the crushed volcanic glass) are used. They are able to rub off a top layer of paper with a line while erasing. At the same time the eraser surface is partially erased. Applying such erasers on the bad-quality paper they can rub it to a hole.
4. The special erasers consisting of rubber only and a plenty of vegetable oil with no abrasive substances at all. During their manufacture vulcanization is rather small. As a result very sticky and easily deformed erasers appear. Owing to strong adhesiveness of such an eraser the top layer of paper which is poorly kept sticks to the eraser very well. This property is used at drawing by coal or dry chalk; their adhesion to a paper is weaker than to an eraser. The pasted traces remain on a surface of an eraser and spoil an eraser gradually.
As times go by rubber erasers become firmer. The process of hardening is accelerated if erasers are on open air or under direct sunbeams, therefore it is recommended to keep them over wrapped. If the storage conditions are kept, erasers save their properties for many years.
Synthetic rubber erasers
Synthetic rubber erasers (or plastic erasers) as a rule have decorative shapes and different color combinations.
These erasers practically don’t cause the static electricity what makes the erasers adhesion to a working surface considerably smaller. Usually vinyl erasers leave wide long crumbs. It means that the smaller amount of movements is needed for removal graphite traces from the work surface; the erasers dust are brushed away from the working surface easily. As opposed to rubber erasers vinyl erasers don’t deteriorate in the course of time.
Several kinds of the vinyl erasers contain microcapsules with solvents. Such erasers are used for erasing ink and multi-markers traces. The very small cells containing solvents inside of an eraser break during erasing. The solvent provides fast clean deleting with no damage of the working surface.
These erasers are used at mechanical erasing lines and traces from a working surface. They contain the abrasive materials and scrapers. But it is necessary to remember that a part of the surface is deleted with lines.
The mechanical glass-fiber eraser has on the end a congestion of narrow fiber glasses which are located parallel inside of the bush that provides their rigidity. When fibers are used up, the moving mechanism submits a new part of fibers. The working part of fibers should be short. These erasers are right for erasing any ink lines and even rust. They are very abrasive and demand the cautious use.
The knife of correction is applied for erasing very thick lines and traces. While erasing a knife blade located perpendicularly to a working surface scrapes the traces. At the deleting it is necessary to be cautious because at strong pressing the working surface is damaged.
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