What types of paper are used for multi-form sheets?

Multi-part, also known as carbonless paper, is paper used for sets of forms (invoices, purchase orders, etc.) so that the data written on the top sheet is transferred to all the other sheets, allowing multiple copies of the same form to be filled in at once. Three sheets of paper comprise carbonless forms:

- Top Sheet: This is carbonless paper that will be directly written on. It is not coated.

- Middle Sheet: This is carbonless paper that has been rear-coated with microencapsulating particles containing dyes. The dyes are typically blue/violet or black in color.

- Back Sheet: This is coated with clay on the upper surface. When pressure is applied, such as when a pen or pencil is writing on the Top Sheet, the microencapsulated dye ruptures and reacts with the clay to form a permanent mark on the Back Sheet, transferring the image.