Bristol board (also referred to as Bristol paper) is a heavyweight paper used for technical drawing, illustration, and other two-dimensional art forms. Its basic size is 22.5″ × 28.5″ (572 × 724 mm) and its bulk thickness is .006 inches (0.15 mm) or higher. Bristol board is rated by the number of plies it contains.
The original bristol board was made in Bristol, England and was a pasted board made of paper containing rags.
Bristol board provides two working surfaces, front and back. This quality separates it from illustration board, which has only a front working surface. The surface texture can vary for different applications, including a smooth plate finish and a medium vellum. Artists working with friction-based media, such as crayon, chalks, or charcoal would use a rougher texture. Smooth finishes are generally more suited to other types of media, such as inks.
So now that you know you can choose the paper for your next project more carefully. Sometimes it really does matter what paper you use. Mixed media artists love the freedom of working with most anything but sometimes you need the right paper for the right job.