Gloss paper surface

Gloss, or surface luster, is the property of a surface to reflect light specularly. It is associated with such phenomena as shininess, highlight, and reflected images. The gloss of paper is usually quantified with a spectrophotometer which measures light at a variety of angles of incidence and reflection. 

The quality of a printed image is greatly enhanced when a coating is applied to the paper surface. Coating the paper lowers the roughness of the surface, generates gloss, provides an ink receptive surface with controlled porosity and improves... 

Depositing pigment particles on the paper surface creates many problems related to the penetration, adhesion and cohesion of these particles, and sometimes results in poor highligter smear resistance, gloss inconsistency of photo prints and the like. 

The gloss of the printed paper is determined by the smoothness of the paper surface and the ink holdout. In turn, the ink holdout is mainly determined by the porosity and the chemical and physical structure of the coated surface. Coatings need to be porous on a microscopic scale so that the soluble component of printing inks is able to penetrate the paper and dry more quickly. The intensity and brilliance of the printed image and the ink consumption depend on the pigments staying on the surface. The hydrophobicity of the coated surface and the surface tension both influence the ink uptake. 

Other types of dryers may be employed for special products or situations. For example, the Yankee dryer, a steam-heated cylinder, 3.7—6.1 m dia, dries the sheet from one side only. It is used extensively for tissues, particularly where creping is accompHshed as the sheet leaves the dryer, and to produce machine-gla2ed papers where intimate contact with the poHshed dryer surface produces a high gloss finish on the contact side. 

Paper absorbency is important for proper ink drying. A paper s surface should allow the ink vehicle to penetrate at the proper rate to achieve proper setting of the ink. If the surface is too absorbent, it causes low ink holdout and loss of gloss. If it is not absorbent enough, it causes ink to transfer to other sheets in a stack, or sheets to stick together. 

---