Paper is the most commonly used items in our daily life, whether it is in writing, painting or reading. Even in the production of industrial and agricultural industry, paper also plays essential and indispensable function. We can’t imagine what our life will be without paper. Paper is a powerful tool in culture communication, science development and production.
Paper is made from cellulose, which abundantly exists in wood. The method of extracting cellulose from wood is mainly paper pulping. There are many types of paper pulping, including mechanical pulping, chemithermomechanical pulping, chemical pulping, recycled pulping, etc.
When the pulp is made, it is time to pressing and drying the pulp to remove the water away and make the pulp as a paper web. Pressing the sheet removes the water by force. A special kind of felt, is used to collect the water; whereas when making paper by hand, a blotter sheet is used instead. Drying refers to remove water from the paper sheets by using air and/or heating; Different forms of heated drying mechanisms such as steam heated can dryerare used to remove water. These heating machines can reach temperatures above 200 °F (93 °C).
Paper Sizing and Coating
The paper need to undergo sizing for various applications. Then coating the paper with a thin layer of material such as calcium carbonate in order to create a surface more suitable for high-resolution halftone screens. Coated papers can be classified into matte, semi-matte or silk, and gloss. Gloss papers give the highest optical density in the printed image. The paper is then fed onto reels if it is used for web printing presses, or cut into sheets for other printing processes or other purposes. The fibres in the paper basically run in the machine direction. Sheets are usually cut “long-grain”, i.e. with the grain parallel to the longer dimension of the sheet.