Rubber cement is an adhesive made from elastic polymers (typically latex) mixed in a solvent such as acetone, hexane, heptane or toluene to keep them fluid enough to be used. Water-based formulae, often stabilised by ammonia, are also available. This makes it part of the class of drying adhesives: as the solvents quickly evaporate, the "rubber" portion remains behind, forming a strong, yet flexible bond. Often a small percentage of alcohol is added to the mix.
Composition
General
Rubber cement is simply a mixture of solid rubber in a volatile solvent that will dissolve it. When the cement is applied, the solvent evaporates, leaving the rubber as the adhesive. Almost any rubber (pre-vulcanized or not) can be used. The rubbers used might be natural rubber, gum mastic or gum arabic. Early solvents used included chloroform and benzene. In the United States of America, current formulations include n-heptane. In the UK, a product called Marabu-Fixogum uses acetone.
Special compositions
Many compositions have included hardeners and/or vulcanizing agents designed to improve the cohesion of the rubber.
Usage
Rubber cement is favored in art applications where easy and damage-free removal of adhesive is desired. For example, rubber cement is used as the marking fluid in erasable pens.
Because rubber cements are designed to peel easily or rub off without damaging the paper or leaving any trace of adhesive behind, they are ideal for use in paste-up work where excess cement might need to be removed. It also does not become brittle as paste does. Older formula rubber cements are not considered an archivally sound adhesive because of their low pH value (acidic) and will cause deterioration of photographs and papers over time. Newer formulas of rubber cement such as Elmer's 'No-Wrinkle' are acid-free and considered "photo safe".
Hazards
The solvents used in rubber cement present some hazards, including flammability and potential for abuse as inhalants. Therefore, as with any adhesive, rubber cement should be used in an open area. Also, care needs be taken to avoid heat sources, as n-heptane and n-hexane are highly flammable. Rubber cement and rubber cement thinner (which is used to replace the solvent that evaporates from the container and to remove stains of glue) that contain acetone will damage polished surfaces and many plastics.
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