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 that could be copied precisely using the diazo copy process; it then found many other uses. The original use for drawing and tracing was largely superseded by technologies that do not require diazo copying or manual copying (by tracing) of drawings.
The transparency of tracing paper is achieved by careful selection of the raw materials and the process used to create transparency. Cellulose fibre forms the basis of the paper, usually from wood species but also from cotton fibre. Often, paper contains other filler materials to enhance opacity and print quality. For tracing or translucent paper, it is necessary to remove any material which obstructs the transmission of light.