Grammage Is A Weight, Not A Thickness
Grammage, written as gsm, is the weight of one square metre of the stock. It correlates with thickness within one paper family but not across families. A 250 gsm uncoated kraft and a 250 gsm coated art paper feel completely different in the hand and behave differently on the folder gluer, because the coating adds weight without adding much bulk.
This is why a specification that only says 250 gsm is incomplete. The useful specification names the family and the finish as well: 250 gsm matt art paper, or 250 gsm brown kraft.
The Working Ranges
- 30 to 160 gsm covers paper bags. The lower end suits light apparel and gift handover, the upper end suits bottles, jars and anything with weight in it.
- 80 to 300 gsm covers signage text stock. Anything hanging unsupported wants 250 gsm or above.
- 157 to 350 gsm covers signage and paperback cover stock, including C1S where the reverse has to take writing or adhesive.
- Folding carton board is specified against the product and the filling line rather than a fixed range, because crease behaviour matters more than weight.
Choosing Between The Families
Brown And White Kraft
Kraft is strong for its weight because the fibres are long and largely unbleached. Brown kraft shows fibre and reads as natural, which is why grocery, bakery and eco led retail default to it. White kraft is the same structural family with a bleached surface, so light artwork and photography reproduce without the brown cast underneath.
Kraft is uncoated, so ink sinks in. Fine reverse type under about 6 pt fills in, and solid colours read duller than the same ink on coated stock. Design to that rather than fighting it.
Art Paper
Coated on both sides, which holds ink on the surface and gives the highest print fidelity. It is the default for photography and heavy solids. Art paper is almost always laminated on a bag or a carton, because the coating scuffs.
Ivory Board And Duplex Board
Heavier boards that hold a square edge. They are used where the structure has to stay rigid, which is why they appear in gifting and cosmetics bags rather than grocery bags.
Specialty Paper
Textured, pearlised and coloured stock where the paper itself is part of the design. Specialty stock is normally paired with foil stamping or blind embossing, because the surface does its work through touch and light rather than through print.
How Lamination Changes The Colour
Matt lamination lowers saturation and lifts the apparent lightness of dark solids. Glossy lamination does the opposite. Both shift the result away from the flat proof, so a laminated job should be approved on a laminated proof. This is the single most common cause of a colour dispute on a finished bag or carton.
A Practical Selection Order
- Decide what the pack has to carry and how it will be handled.
- Choose the family: kraft for strength and natural look, art paper for print fidelity, board for rigidity, specialty for tactile effect.
- Set the grammage inside that family against the load.
- Add the finish, then re-check the artwork against the finish rather than against plain stock.
- Ask for the physical sample before the artwork is locked.
