the product can be manufactured without gluing, with internal gluing or with internal and surface gluing.
internal gluing avoids, or retards, the penetration of water and other fluids, although it is not waterproof or resistant to moisture. It does not prevent the penetration of the ink vehicle into the product.
external gluing, in addition to the above, improves the surface resistance of the product, the graphic ink anchoring and resistance to abrasion, to traction, to folding, etc.