Solid unbleached board, also known as SUB, is a grade of paperboard typically made of unbleached chemical pulp. Most often it comes with two to three layers of mineral or synthetic pigment coating on the top and one layer on the reverse side. Recycled fibres are sometimes used to replace the unbleached chemical pulp.
- Stora Enso (2008), Paperboard Guide
- Twede, Diana; Selke, Susan E. M. (2004), Cartons, Crates and Corrugated Board: Handbook of Paper and Wood Packaging Technology, Lancaster, PA: DasTech Publications
- Pro Carton (2009). "Types of Cartonboard". Retrieved 2009-09-22.