Cotton paper

Cotton paper, also known as rag paper or rag stock paper, is made using a cotton linter or cotton from used cloth (rags) as the primary material. Important documents are often printed on cotton paper, because it is known to last many years without deterioration. Cotton paper is superior in both strength and durability to wood pulp-based paper, which may contain high concentrations of acids, and also absorbs ink or toner better. Different grades of cotton paper can be produced.
Properties.
High-quality 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 can more readily absorb ink or toner.
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 bond paper can be found at most stores that sell stationery and other office products. Some cotton paper contains a watermark. It is used for banknotes in a number of countries. These banknotes are typically made from 100% cotton paper, but can also be made with a mixture of 75% or less flax. Other materials may also be used and still be known as "currency paper". 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.