What does C1S and C2S mean?

C1S

Paper coated one side.

C2S

Paper coated on two sides.

Not to be confused with UV and aqueous coatings or laminates, the terms C1S and C2S refer to paper coated at the manufacturing stage, prior to printing. Coated paper has a smoother printing surface and lower ink absorption than uncoated paper. This means the coated paper has brighter more vibrant colours than uncoated.