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Paper & Pulp Dictionary Glossary "F"

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 Definitions for commonly used terms, words and phrases used in the pulp and paper trade



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Fabric Press
Paper machine wet press that uses a special multiple weave fabric belt sandwiched between the regular felt and the rubber covered roll, increasing the capacity to receive and remove water from the nip between the rolls.
Falling Film Evaporator
A type of heat exchanger used for concentrating a solution consisting of a non-volatile solute and a volatile solvent; solution flows downward on the heat exchange surface by gravity; the heat exchange surface is typically a bundle of plates, lamellas or tubes; commonly used in pulp mills and chemical recovery process.
A dimensional change in paper associated with its passage through a printing unit. In web offset printing it is the increase in web width after each blanket impression.
Fan Pump
A high flow rate, low head pump used to pump diluted stock to paper machine headbox.
Continuous multiple ply form manufactured from a single wide web which is folded longitudinally.
The tendency of liquid ink to spread along the paper fibers so that the image produced does not have sharp, clean edges.
A woven cloth used to carry the web of paper between press and dryer rolls on the paper machine.
Felt Finish
Surface characteristics of paper formed at the wet end of a paper machine, using woven wool or synthetic felts with distinctive patterns to create a similar texture in the finish sheets.
Felt Mark
Imprint left on the paper by one or more of the felts used in making the paper. The mark may be wanted or unwanted and special effects can be introduced in this way.
Felt Side
The side of the paper which does not touch the wire on the paper machine. The "top side" or felt side is preferred for printing because it retains more fillers.
Fiber or Fibre
The slender, thread-like cellulose structures that forms the main part of tree trunk and from separated and suitably treated, cohere to form a sheet of paper.

Softwood Fiber                                                                                                   Fiber Internal Structure

Fiber Axis Ratio
Ratio of fiber width to fiber thickness.
Fiber Coarseness
Weight per unit length of fiber.
Fiber Cut
A fiber cut is a short, straight cut located on the edge of the web, caused by a fiber imbedded in the web of paper.
Fiber Debris
Pieces of material which has been separated from the main body of the fiber..
Fiber Floc
Fibers that have agglomerated as a result of poor formation.
Fiber Orientation
Refers to the alignment of the fibers in the sheet.
Board made from defibrated wood chips, used as a building board.
A structural change occurring in the walls of chemical pulp fibers during beating.
Fibrillae or Fibrils
String-like elements that are loosened from the paper fibers during the beating process. They aid in the bonding processes when paper is being manufactured.
Any inorganic substance added to the pulp during manufacturing of paper.
Filter Paper
Unsized paper made from chemical pulp, in some cases also with an admixture of rags, sometimes with a wet strength finish. Filtration rate and selectivity, which are both dependent on the number and the size of the pores, can be controlled by specific grinding of the pulps and creping.
The effluent from the washing or filtering process.
Small particles fiber defined arbitrarily by classification.
Fine Papers
Uncoated writing and printing grade paper including offset, bond, duplicating and photocopying.
The surface characteristic of a sheet created by either on-machine or off-machine papermaking processes. Popular text and cover finishes include smooth, vellum, felt, laid, and linen.
The trimming, winding, rewinding and packing of paper rolls or trimming, cutting, counting and packing of paper sheets from parent roll.
Finishing Broke
Discarded paper resulting from any finishing operation.
First Pass Retention
First-pass retention gives a practical indication of the efficiency by which fine materials are retained in a web of paper as it is being formed. First-pass retention values can be calculated from just two consistency measurements, the headbox consistency, and the white water consistency. There is a very wide diversity of first-pass retention on different paper machines, from less than 50% to almost 100%. The key rules that papermakers follow are that (a) first-pass retention should have a steady value, and (b) that value should be high enough to avoid operational problems or an excessively two-sided sheet. Some operational problems that can be caused by low values of first-pass retention are increased frequency of deposit problems, filling of wet-press felts, poor drainage, and unsteady drainage rates and sheet moistures.
Fish Eye
A paper defect appearing as glazed, translucent spot caused by slime, fiber bundles, and/or improperly prepared chemical additives in the stock. 
A strip of paper protruding from a roll or skid of paper. May be used to mark a splice in a roll of paper or used to mark off reams in a skid. 
Flame Resistant
Treatment applied to kraft paper to make it resistant to catching on fire (not fire proof—will char but not burst into flame).
Flat Crush of Corrugated Board
A laboratory test (Tappi T808 or T825) of a single wall combined board specimen to measure its resistance to crushing forces from conversion and handling. Test can also be an indicator of flute formation and the presence of crushed or leaning flutes.
Spontaneous boiling and cooling of a liquid caused by the reduction of pressure below the vapor pressure of the liquid. Flashing occurs in blow tank during blowing.
Fly Leaf/Shaving
Trim scrap from printing operation.
A form of rotary letterpress using flexible rubber or photopolymer plates.
Flexural Rigidity
The measurement of a combined board resistance to flexing. Combined with ECT box perimeter and flute type, it is key to predicting box compression resistance or static load resistance (Tappi T566).
Flotation Cell 
Main equipment of Flotation Deinking, Large number of  tiny air bubbles are injected into the cleaned pulp, the free ink particles attach themselves to these bubbles and float to the surface where it is skimmed off and removed. 
Flotation Deinking
Using flotation method for removing ink from paper during the de-inking process.
Flotation Dryer
Non contacting dryer used in pulp drying or coating applications, drying is achieved by passing sheet between two dryer hoods where hot dry air is impinged onto the sheet and the moisture is evaporated and removed by an air system.*
Fluff Pulp
A chemical, mechanical or combination of chemical/mechanical pulp, usually bleached, used as an absorbent medium in disposable diapers, bed pads and hygienic personal products. Also known as "fluffing" or "comminution" pulp
Fluorescent Dye
A coloring agent added to pulp to increase the brightness of the paper. It may give a slight blue or green cast to the sheet.
Fluorescent Inks
Printing inks that emit and reflect light. Generally, they are brighter and more opaque than traditional inks, but they are not color fast, so they will fade in bright light over time. Their metallic content will also affect dot gain and trapping.
Fluorescent Whitening Agent
Also referred to as an "optical brightener." A chemical compound when expose to a light containing an ultraviolet component will absorb and re-emit light in the blue spectrum or in other words fluoresce. FWA's will enhance brightness and blueness quality of white paper.
One of the wave shapes pressed into corrugated medium. Flutes are categorized by the size of the wave. A, B, C, E and F are common flute types, along with a variety of much larger flutes and smaller flutes.

Fluted Edge Crush
Measures the edgewise compression strength of corrugating medium using a fluted test specimen per Tappi T824.
Flute (A,B,C,E,F&G)
These letters define the type of corrugated material in terms of the number of corrugations per unit length and the height of the corrugations - specifically these are:
Flute Corrugations per metre Height of corrugation (mm)
A 105 - 125 4.5 - 4.7
B 150 - 185 2.1 - 2.9
C 120 - 145 3.5 - 3.7
E 290 - 320 1.1 - 1.2
F 410 - 420 0.7 - 0.8
G 550 - 560 0.5 - 0.6
Waves or corrugation in heat-set web offset prints that runs in the press direction.
C1S paperboard designed for lamination to a foam backing for point-of-purchase displays, posters, and signs.
Foil of Hydrafoil
The flat strip used to support wire. Only the leading edge of the wire touches the foil. Foil helps in removing water by creating gentle suction and also doctor the water removed in previous section.

Doubling up a sheet of paper so that one part lies on top of another. Folding stresses the paper fibers. To create a smooth, straight fold, heavy papers like cover stocks and Bristol need to be scored before they're folded.
Folding Boxboard
Single or multi-layer paperboard made from primary and/or secondary fibers, sometimes with a coated front, used to make consumer packaging (cartons).
Folding Strength or Folding Endurance
Folding strength is most important in currency paper. Multiple fold strength is also important for paper used in books, maps, and pamphlets. It's far less important in one-fold greeting cards or envelopes, where fold cracking is the vital consideration. Folding endurance or strength is measured and reported in numbers.
The dispersion of fibers in a sheet of paper. The more uniform and tightly bound the fibers, the better the sheet will print and look. Close Formation - Uniform distribution of fibers.  Cloudy formation: A spotty, non-uniform dispersion of  fibers, the opposite of close formation.
Forming Board
Forming Board is the leading forming unit under the fabric closest to the slice. The stock jet velocity, the impingement angle and the position of the impingement onto the forming board will determine the water removal and the activity produced at this point. Modern Forming Boards are stepped to create activity at high speeds – this greatly enhances the formation.
Fountain Roller
The roller on a printing machine which initiates the supply of moisture to the damping system.
Four-color Printing Process
A printing method that uses dots of magenta (red), cyan (blue), yellow, and black to simulate the continuous tones and variety of colors in a color image. Reproducing a four-color image begins with separating the image into four different halftones by using color filters of the opposite (or negative) color. For instance, a red filter is used to capture the cyan halftone, a blue filter is used to capture the yellow halftone, and a green filter is used to capture the magenta halftone. Because a printing press can't change the tone intensity of ink, four-color process relies on a trick of the eye to mimic light and dark areas.

Each halftone separation is printed with its process color (cyan, magenta, yellow, and black). When we look at the final result, our eyes blend the dots to recreate the continuous tones and variety of colors we see in a color photograph, painting, or drawing.

Named after its inventor, the Fourdrinier papermaking machine is structured on a continuously moving wire belt on to which a watery slurry of pulp is spread. As the wire moves, the water is drained off and pressed out, and the paper is then dried.
Free Stock
Unrefined stock. Stock that, when drained under gravity, parts easily with the water of suspension
A term used to define how quickly water is drained from the pulp. The opposite of freeness is slowness. Freeness or slowness is the function of beating or refining. Freeness and slowness reported in ml CSF and degree SR respectively are also the measurement of degree of refining or beating.
Paper that is free of mechanical wood pulp, which is true of virtually all fine printing papers.
French Fold
A sheet printed on one side and folded first vertically and then horizontally to produce a four-page folder.
Fully Bleached Pulp
Pulp that has been bleached to the highest brightness attainable (> 60 ISO).
A blend of fibers, pigments, dyes, fillers and other materials that are fed to the wet end of the paper machine.
Fibrous projections on the surface of a sheet of paper, caused by excessive suction, insufficient beating or lack of surface sizing. Lint appears in much the same manner but is not attached to the surface.
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