Tracing paper is paper made to have low opacity, allowing light to pass through. It was originally developed for architects and design engineers to create drawings which could be copied precisely using the diazo copy process; it then found many other uses.
The transparency of the paper is achieved by careful selection of the raw materials and the unique process used to create transparency. Cellulose fiber forms the basis of the paper, usually from wood species but also from cotton. Often, paper contains other filler materials to enhance opacity and print quality. However, during the creation of tracing paper, it is necessary to remove any extraneous materials which obstruct the transmission of light.