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Exhaust Fans

Fans used to remove moisture laden air from the dryer hoods.


A change in the dimensions, usually cross grain direction, of a sheet of paper due to absorption of moisture.

Extensible Paper

A stretchable paper with a smooth appearance and high energy absorption properties. A controlled amount of stretch to meet specifications may be imparted in a number of ways, either on or off the paper machine by methods generally differing from those used to produce creped papers. Extensible papers, made in a variety of basis weights and grades, are used for multi-wall sacks, packaging, converting, laminating, wrapping, etc.


A plastic mesh screen used to form the sheet on the Fourdrinier or former.

Fan Pump (Secondary)

The pump used to deliver the slurry of stock, water, and additives to the head box

Fan Shower

A shower used on the machine with a stream of water discharged in the shape of a fan. Used for felt wetting and lubrication on Uhle boxes.


The process of manually inspecting skids of paper for visible defects.


That property of a paper or dyestuff which renders it resistant to change in color. Depending on its use, a paper should be light-proof, alkali and acid-proof.


A woven endless belt used to carry the web of paper between the press and dryer rolls on the paper machine. The felt also provides a cushion between the press rolls and serves as a medium for the removal of water from the wet sheet. Felts are usually referred to according to use, as follows: (1) bottom felt, (2) dryer felt, (3) pick-up felt, (4) press felt, (5) top felt, and (6) wet felt.

Felt Extreme Position Indicator

This is the warning palm located on the front and reverse of the felt or wire by a guide roll. Gives a warning if felt is running off the machine.

Felt Mark

An imperfection in paper caused by some coarse or grainy character of the felt after it has become worn, or filled with extracted material disrupting its porosity, disturbing the uniform expulsion of water from the web of paper.

Felt Side (Top Side)

(1) On a Fourdrinier the side of the sheet which does not contact the fabric. On a twin wire former where both sides come in contact with the fabric, it would be the top side. (2) The side of a sheet of paper opposite to the wire side of the sheet; this is the top side of the sheet when it is formed on the wire.


The unit cell of vegetable growth which is many times longer than its diameter and which is the unit of paper pulps. Fibers are sometimes divided into two classes, bast and wood, but they are best designated by means of the tissue or region in which they occur, as cortical fibers, pericyclic fibers, phloem fibers, wood fibers, leaf fibers, etc. Other types of fiber such as mineral, animal and synthetic are also used to a certain extent in making special types of papers.

Fiber Analysis

A microscopic process of determining the constituents in a given sheet of paper.

Fiber Count

The percentage of hardwood and softwood fibers used to make sheet. Determined by counting the fibers under a microscope.


The maximum width of paper that can be made on any given paper machine.


A synonym for loading; the minerals used to improve the printing properties of paper.


Paper materials used to fill spaces not occupied by paper.


Application of a light pigmented coating to provide a more uniform and smoother surface.

Filter Paper

Made of soft pulp or occasionally with unsized waterproof paper that has rag additive. Filtration speed and release capability (separation factor) are both dependant on the amount and size of the pores. They are additionally influenced by various degrees of pulp refining and by creping.