cartridge paper 
noun [mass noun] British
Thick, rough-textured paper used for drawing and for strong envelopes.You need ordinary envelopes and cheap cartridge paper or newsprint....
- The fine tones of watercolors are recreated on top-quality cartridge paper, identical to the original, according to company officials.
- So how did you get into this business, I ask, as he sets up a crisp new sheet of white cartridge paper on his easel.
Origin
Mid 17th century: originally used to make cartridge cases.