Cotton paper is made from cotton linters or cotton from used cloths (rags) as the primary material source, hence the name rag paper. Cotton paper is superior in both strength and durability to wood pulp-based paper, which may contain high concentrations of acids.
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Properties
Certain cotton fibre paper is known to last hundreds of years without appreciable fading, discoloration, or deterioration, so it is often used for important documents such as the archival copies of dissertations or theses. As a rule of thumb, for each percentage point of cotton fibre, a user may expect one year of resisting deterioration by use (the handling to which paper may be subjected). Legal document paper typically contains 25% cotton. Cotton paper will produce a better printout than copy paper because it is able to absorb ink/toner better.
Cotton paper is typically graded as 25%, 50%, or 100% cotton. Usually it can be checked by holding the cotton paper up to the light and looking just below the watermark for a number. 100% Cotton paper may contain small amounts of acids, and should be tested or certified before use for archival documents.
Second-cut cotton linters have a normal average fibre length of 1.45 µm, and have similar properties as a short softwood pulp.
Uses
Cotton paper is used in some countries’ modern banknotes. These banknotes are typically made from 100% cotton paper, but can also be made from a mixture of 75% or less flax. Other materials may also be used and still be known as Currency paper.
Cotton bond paper can be found at most stores that sell stationery and other office products. Some cotton paper contains a watermark.
Higher quality art papers are often made from cotton.
It has found extensive use as a Printed Circuit Board substrate when mixed with epoxy resins and classified into CEM 1, CEM 2 etc.
History
Cotton was first used with a mixture of silk to make paper called Carta Bombycina. In the 1800s, fiber crops such as flax fibres or cotton from used cloths (rags) were the primary material source. By the turn of the 20th century, most paper was made from wood pulp, but cotton is still used in specialty papers. As cotton rags now often contain synthetic fibres, papermakers have turned to second-cut cotton linters as raw material sources for making pulp for cotton papers.