The common handheld tool used to correct pencil marks, known as an eraser, appears simple, yet its composition represents a long evolution of material science. While its history is rooted in natural, botanical sources, modern manufacturing relies heavily on engineered polymers. The material used depends entirely on the specific type of correction tool, meaning the question of whether an eraser is natural or synthetic no longer has a single answer.
The History of Natural Rubber Erasers
The original successful eraser was derived from latex, the milky fluid collected from the Hevea brasiliensis tree. Before this discovery, people used materials like wax or wadded-up bread to remove graphite marks. In 1770, English chemist Joseph Priestley observed that this plant-derived gum could rub out pencil lines. He is credited with coining the term “rubber” because of its purpose in rubbing away marks.
Raw, natural rubber (caoutchouc) was initially brittle when cold and sticky when warm, making it unreliable. A significant improvement came in 1839 with Charles Goodyear’s invention of vulcanization, a process that stabilizes the rubber by cross-linking its polymer chains with sulfur. This chemical modification made the material far more durable and usable, allowing for the widespread commercial production of the first block erasers. The rubber works because its polymer matrix is stickier than the paper fibers, allowing it to adhere to and lift the loose graphite particles.
The Development of Synthetic Alternatives
Reliance on a single natural source for rubber created volatility in cost and supply, spurring the development of synthetic alternatives. By the mid-20th century, chemists engineered polymers specifically designed to replicate or improve upon natural rubber’s function. This shift was accelerated by the need for greater durability and to avoid allergic reactions associated with natural latex.
One widely adopted early synthetic material was Styrene-Butadiene Rubber (SBR), a petroleum-derived elastomer whose formula could be adjusted to produce erasers with varying hardness and color. Another alternative was polyvinyl chloride (PVC), a thermoplastic mixed with plasticizers to create a soft, flexible material. These synthetic compounds offered superior shelf stability and resistance to cracking. The ability to precisely control the properties of these polymers allowed manufacturers to create specialized erasers for different artistic and technical applications.
Modern Eraser Types and Their Composition
Today, the market is dominated by synthetic materials, though the composition varies widely across different eraser types. The common pink or block erasers, often found on the end of pencils, are typically made from synthetic rubber, such as SBR, or a blend of natural and synthetic rubber. These types function by slightly shedding or crumbling as they are used, which carries the lifted graphite away from the paper surface. The shedding action helps prevent the smearing of marks as a fresh, clean surface is continuously presented to the paper.
White plastic or vinyl erasers are predominantly composed of PVC or similar thermoplastic elastomers, a material known for its clean erasing and minimal residue. These erasers are often preferred by draftsmen and artists because they are capable of lifting marks without damaging more delicate paper surfaces. Because of the nature of the vinyl polymer, they are often softer and less abrasive than many rubber compounds.
Specialized Art Erasers
Art gum erasers and kneaded erasers represent more specialized, complex blends designed for fine art applications. Gum erasers are soft and crumble extensively, which helps absorb large amounts of graphite over a wide area, making them gentle on the paper’s surface. Kneaded erasers are highly pliable and work by adsorption, lifting the charcoal or graphite from the paper without shedding any material. While the base material in both gum and kneaded types may be a form of synthetic compound, they contain fillers like vegetable oil or other plasticizers to achieve their unique texture and function.