Glossary
broke: waste paper, either made during a sheet break or trimmings. It is gathered up and put in a repulper for recycling back into the process.
consistency: the percent dry fiber in a pulp slurry.
couch: French meaning to lie down. Following the couch roll the sheet is lifted off the wire and transferred into the press section.
dandy roll: a mesh covered hollow roll that rides on top of the fourdrinier. It breaks up fiber clumps to improve the sheet formation and can also be used to make an imprint, as with laid paper. See also watermark.
fan pump: the large pump that circulates white water from the white water chest to the headbox. The flow may go through screens and cleaners, if used. On large paper machines fan pumps may be rated in tens of thousands of gallons per minute.
felt: a loop of fabric that goes between press rolls and serves as a place to receive the pressed out water. Felts also support the wet paper web and guide it through the press section. Felts are also used in the dryer section to keep the sheet in close contact with the dryers and increase heat transfer.
filler: a finely divided substance added to paper in the forming process. Fillers improve print quality, brightness and opacity. The most common fillers are clay and calcium carbonate. Titanium dioxide is a filler but also improves brightness and opacity. Use of calcium carbonate filler is the process called alkaline sizing and uses different chemistry than acid sizing. Alkaline sized paper has superior aging properties.
formation: the degree of uniformity of fiber distribution in finished paper, which is easily seen by holding paper up to the light.
headbox: the pressure chamber where turbulence is applied to brake up fiber clumps in the slurry. The main job of the headbox is to distribute the fiber slurry uniformly across the wire.
nip: the contact area where two opposing rolls meet, such as in a press or calender
pH: the degree of acidity or alkalinity of a solution. Alkaline paper has a very long life. Acid paper deteriorates over time, which caused libraries to either take conservation measures or replace many older books.
size: a chemical (formerly rosin derived but now a different chemical) or starch, applied to paper to retard the rate of water penetration. Sizing prevents bleeding of ink during printing, improving the sharpness of printing.
slice: the adjustable rectangular orifice, usually at the bottom of the headbox, through which the whitewater jet discharges onto the wire. The slice opening and water pressure together determine the amount and velocity of whitewater flow through the slice. The slice usually has some form of adjustment mechanism to even out the paper weight profile across the machine (CD profile), although a newer methods is to inject water into the whitewater across the headbox slice area, thereby using localized consistency to control CD weight profile.
stock: a pulp slurry that has been processed in the stock preparation area with necessary additives, refining and pH adjustment and ready for making paper
web: the continuous flow of un-dried fiber from the couch roll down the paper machine
white water: filtrate from the drainage table. The white water from the table is usually stored in a white water chest from which it is pumped by the fan pump to the headbox.
wire: the woven mesh fabric loop that is used for draining the pulp slurry from the headbox. Until the 1970s bronze wires were used but now they are woven from coarse mono-filament synthetics similar to fishing line but very stiff.
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