Volume 1, Number 5
Nov 1993

Paper Definitions

The following definitions are taken from Handbook of Pulp & Paper Terminology: A Guide to Industrial and Technological Usage, by Gary A. Smook (Angus Wilde Publications, Bellingham, WA, 1990) and are reprinted with permission of the author. The Handbook presents terms commonly used within the paper industry, in the language of those who use them. As the author says in his preface, the complex and constantly changing technology in this industry continually creates new terms and modifies old ones; furthermore, terms have different meanings in different regions, different sectors of the industry, and different contexts. The author's definitions reflect generally accepted usage.

These definitions were chosen simply because they should be interesting to people outside the paper industry.

DIAZOTYPE BASE PAPER: Smooth, sized paper manufactured from bleached chemical pulp having high tear and folding strength. Suitable papers for diazotype coating also must be chemically inert and free from metallic ions that could adversely affect the photochemical process.

HANGING RAW STOCK: Bulky, hard-sized, toothy-surfaced groundwood paper, which is manufactured in a wide range of grammages for conversion into wallpaper. It is usually coated by the converter and then printed and/or embossed.

NOISELESS PAPER: Bulky, unsized paper made from rag and chemical pulpblends, used for theater programs, studio manuscripts and other applications where the rustle and rattle of paper is objectionable. Syn. Silent Paper.

PIGMENTED PAPER: Paper which has been given a thin pigmented coating, usually at the size press. The coat weight normally does not exceed 5 g/m2 on either side. Pigmented papers bridge the quality gap between groundwood papers and publication grades. In the trade, they are referred to as machine finished, pigmented (MFP) grades. Syn. Semicoated Printing Paper, Slightly Coated Paper.

PRESSBOARD: Hard-calendered board, usually made on an intermittent board machine from 100% chemical pulp, having characteristics of high chemical purity, high density, even thickness, surface smoothness, high strength, and good electrical insulation properties; used for pressing fabrics and as layer insulation in electrical transformers. Syn. Transformer Board, Textile Board.

RUST-INHIBITOR PAPERS: Wrapping papers used for steel articles, that have been impregnated or coated with synthetic rust-inhibitor chemicals.

SENSITIZED PAPERS: Papers that have been treated with a chemical solution to make them surface reactive to light, chemicals or gases. Included in this group are various copy and photographic papers.

THERMAL PAPER: Lightweight paper with a one-sided application of heat sensitive coating, used for facsimilies, computer printouts and medical imaging applications.

VULCANIZING PAPER: Waterleaf paper made of rag and/or chemical pulp, with high chemical purity and controlled cupriethylenediamine viscosity.

Comments and clarifications:

"Pigments" in the paper industry may be colorful, but are often white. The term usually refers to clay, calcium carbonate and titanium dioxide used as fillers and coatings.

The size press is a roll press in the dryer section that applies thin coatings or treatments to paper, spreading the additive across the surface like a glue machine or wax coater spreads glue or wax. It can apply surface sizes, but this is not its only function. It is used for a wide and growing number of treatments.

Waterleaf paper is paper made without sizes, pigments or other additives. Viscosity is a measure of the average molecular weight of cellulose, and therefore an indication of degradation. The lower the viscosity, the more degradation has taken place.