Flexo Glossary
Flexographics from A to Z
A B C D E F G H I J K L M N O P Q R S T U V W X Y Z
A
- Acetate
- A family of solvents also known as esters; example normal propyl acetate. One of, or the family of, cellulose acetate films.
- Acetone
- A very active solvent used mainly in gravure inks. The fastest drying solvent in the ketone family.
- Alcohol
- A group of organic solvents widely used in flexographic inks.
- Aliphatic Hydrocarbons
- Solvents obtained by fractionation of crude petroleum oil. Examples are textile spirits, VMP Naphtha, gasoline and kerosene. Frequently used as part of the solvent mixture in "co-solvent" and "polyamide" type flexo inks, in conjunction with Buna-N type plates and rollers; tend to swell natural and butyl rubber.
- Ambient Temperature
- A term used to denote the temperature of the surrounding air.
- Anilox Roll
- Mechanically- or laser-engraved steel and chrome-coated metering roll used in flexo presses to meter a controlled film of ink from the contacting elastomer covered fountain roller to the printing plates which print the web. Volume of ink is affected by the cell count per linear inch and dimension of the cell and cell wall of the engraving. Manufactured from copper and chromium plated steel. Also given a coating of aluminum oxide (ceramic) or copper and chrome.
- Anilox System
- The inking system commonly employed in flexographic presses consisting of an elastomer covered fountain roller running in the ink pan, adjustable against a contacting engraved metering roll, the two as a unit adjustable to the printing plate roll, elastomer design roll or plain elastomer coating roll as the case may be. Ink is flooded into the engraved cells of the metering roll, excess doctored off by the wiping or squeezing action of the fountain roll or a doctor blade and that which remains beneath the surface of the metering roll is transferred to the printing plates.
- Antifoaming Agent
- An additive used in ink that prevents or eliminates foaming of a liquid or breaks foam already formed.
- Artwork
- The original design, including drawings and text, produced by the artist. All elements of the design from which the black and white art and printing plates are made; also refers to all of the black and white production art.
B
- Back Exposure
- UV light exposure through the back of the plate which sensitizes the plate and sets the floor.
- Bare Cylinder Diameter
- The diameter of the actual plate cylinder, before the sticky-back and plates are mounted.
- Binder
- The adhesive components of an ink, normally supplied by the resin formulation; the ink vehicle. In paper, an adhesive component used to cement inert filler, such as clay, to the sheet or to affix short fibres firmly (securely) to paper or board stock.
- Bleeder Strips
- See Masking Strips.
C
- Capped Plate
- A photopolymer printing plate with a surface layer of coating (cap) that is intended to enhance ink transfer and print quality.
- Character
- Each individual letter, symbol or punctuation mark that makes up a full typeface.
- Colour Balance
- See Grey Balance.
- Colour Proof
- A printed or simulated printed image of each process colour (cyan, magenta, yellow and black) using inks, toners or dyes to give a simulated impression of the final printed reproduction.
- Colour Overlap
- The slight extension of one colour over another.
- Colour Overlay
- A transparent overlay, usually acetate, on a Black & White drawing on which each additional colour is indicated as a guide for reproduction. A term sometimes used at press-side referring to the number of colours which overprint each other.
- Colour Separation
- Film intermediates made from the colour originals to determine and reproduce the proportional amount of cyan, magenta, yellow and black in the original. These films are used to produce printing plates for each colour.
- Colourant
- The colour portion of the ink which may be pigment or dye or a combination of the two.
- Compatible
- Refers to the ability to mix differing solutions or material together as a homogenous mixture, without resulting in "kick-out" or haziness.
- Continuous Tone
- A photographic image that has not been screened and contains graduated tones from black to white.
- Contrast
- The tonal gradation between the highlights, middle tones and shadows in an original or reproduction.
- Converter
- Refers to that type of manufacturer who produces printed rolls, sheets, bags or pouches, etc., from printed rolls of film, foil or paper.
- Copy
- Material, including art and text, submitted for reproduction. The term is also used to refer to the final printed result.
- Co-Solvent
- One of two or more solvents in a mixture which together dissolve a solid.
- Coversheet
- Layer of clear material that is taped, laminated, or used to cover and protect a surface from damage, dust, dirt, etc.
- Crop
- Marks Marks made on the outer edges of artwork to designate the area to be printed.
- Cromalin®
- Off-press colour proofs using DuPont Cromalin® materials.
- Cyan
- One of the subtractive primaries the hue of which is used for one of the 4-colour process inks. It reflects or transmits blue and green light and absorbs red light.
- Cylinder
- In flexography, for no particular reason, most rollers in the printing press are called rolls with the exception of that upon which the rubber plates are mounted, and the one which receives the impression, and these are usually referred to as cylinders (i.e., plate cylinder or impression cylinder).
D
- Deep Relief Plates
- Plates commonly used in the corrugated market. These plates will yield a relief up to 3.175mm/0.125².
- Delamination
- The partial or complete separation of the layers of a laminate.
- Densitometer
- Instrument that measures reflected or transmitted light. A reflection densitometer is used as a control instrument to check the uniformity and consistency of print colour.
- Density
- The mass of a unit volume; opacity; colour strength. The degree of darkness (light absorption or opacity) of a photographic image.
- Dimensional Stability
- Ability to maintain size. Resistance to dimensional change resulting from the ambient atmosphere or other conditions.
- Distortion
- Distortion See Film Reduction.
- Doctor Blade
- A thin flexible blade mounted parallel to and adjustable against an engraved anilox roll, for the purpose of scraping off excess ink.
- Dot
- The individual element of a halftone.
- Dot Gain
- Increase in size of a dot from the film to the printed sheet. All printing processes have dot gain which consist of two parts, physical dot gain and optical dot gain due to the physics of light absorption and reflection. This causes darker tones or stronger colours.
- Dropout
- A halftone in which the extreme highlights do not reproduce.
- Drying
- During the processing, the plate absorbs solvent which must be removed by drying which is carried out in an oven at a temperature of 60°C (14060°C (140°F)).
- Durometer
- The measure of plate hardness usually made with a Shore "A" durometer gauge.
- Dyes
- Colouring material which is soluble in an ink vehicle as opposed to pigments which are not soluble and must be dispersed.
E
- Edge Sealant
- A sealing agent placed at the leading and trailing edges of the plate to secure the laydown of the plate to the plate cylinder for press runs.
- Elastomeric
- Flexible and resilient.
- Elongation
- Longitudinal deformation resulting from stress, from stretching.
- Emulsion
- A type of mixture wherein two or more immiscible (or unmixable) materials are held together in a homogenous mixture by the action of a third agent. The term "emulsifying agent" is applied to the material which is added to hold the emulsion. Differs from a solution in which one material is dissolved in another.
- Engraving
- A general term normally applied to any pattern which has been cut in or incised in a surface by hand, mechanical or etching processes.
- Ester
- A group of solvents made by reacting an acid with an alcohol, e.g., ethyl acetate, isopropyl acetate, "acetate" solvents.
- Expose
- To subject (a sensitive film, plate, etc.) to the action of lights.
F
- Fill-In
- Generally used to refer to the open portions of small type and halftones filled by over exposure (most -commonly).
- Film Reduction
- Intentional around-cylinder compensation of the image to address flexographic plate printing characteristics.
- Flexography
- A method of direct rotary printing using resilient raised image printing plates, affixed to variable repeat plate cylinders, inked by a roll or doctor-blade-wiped engraved metal roll, carrying fluid or paste-type inks to virtually any substrate.
- Floor
- The base of the plate which supports the relief image of the plate. The floor is calculated by subtracting the relief from the total plate thickness.
- Fountain
- A pan or trough on a flexographic press in which the fountain roller revolves. Sometimes loosely applied to the entire printing station.
- Fountain Roll
- Roll that picks up the ink or coating material from the fountain and applies it to the transfer roll.
- Four-Colour Process
- Printing with yellow, magenta and cyan colour inks plus black, using screens to create all other colours.
G
- Gear Streaks
- Parallel streaks appearing across the printed sheet at the same interval as gear teeth on the cylinder.
- Grey Balance
- The ratio of the densities of the three process inks (yellow, magenta, and cyan) required to produce a neutral grey. The actual ratio is different at each specific tint value. Predominantly a function of ink hue.
- Grey Scale
- A strip of standard grey tone values ranging from white to black.
H
- Halftone
- The reproduction of continuous-tone artwork through a contact screen. Photographic image formed by a pattern of discrete dot sizes. Dots vary in area and shape but have uniform density. Creates the illusion of continuous tone when seen at a distance.
- Halo
- An undesirable peripheral outline of the printed image. A blurred effect usually occurring in highlight areas.
- High Intensity Bulbs
- Exposure lamps that emit a greater intensity of light energy than standard bulbs. The use of these bulbs reduces exposure times in platemaking.
- Highlight
- The lightest or whitest parts in a picture. Represented in a halftone reproduction by the smallest dots or the absence of dots.
- Hue
- The characteristic by which one colour is distinguished from another. The predominate wavelength reflected by a coloured material which determines its position in spectral or chromatic scale; (e.g. red, blue, yellow). It is the major colour attribute of which there are mass-tone shades and tints.
- Hydrometer
- An instrument for measuring the specific gravity of a liquid.
I
- Image Areas
- The area of the printing plate which transfers ink to the substrate. The printed area of a receiving surface.
- Impression
- The pressure of type, plate or blanket as it comes in contact with the substrate. The image transferred from the printing plate to the substrate. The adjustment required to effect the above.
- Impression Cylinder
- Roller or cylinder which backs up or supports the web at the point of impression.
- Ink, Flexographic Fast drying fluid or paste type inks used in flexographic printing.
- Ink Fountain
- The ink pan or trough on a flexo press which stores and supplies ink to the inking rollers.
- Insoluble Incapable of being dissolved in a liquid.
- Ionizers
- Tool used to eliminate static. Neutralizes static charges by the use of blowing ionized air over the charged surface. Static charge is responsible for the attraction of contaminants (dust, dirt).
L
- Latitude
- The range of exposure within which a film or plate will produce a negative or positive image of satisfactory quality.
- Light Finishing
- Detacking of plate surface by short wavelength UV germicidal light exposure.
- Light Intensity
- The amount of light energy transmitted.
- Line Copy (Linework)
- Copy made up of solids and lines in contrast to halftones or shadings made up of a series of dots. Any copy suitable for reproduction without using a halftone screen.
- LPI
- lines per inch. See Screen Ruling
M
- Magenta
- One of the subtractive primaries the hue of which is used for one of the 4-colour process inks. It reflects or transmits blue and red light and absorbs green light.
- Main Exposure
- UV light exposure of the plate through a film negative to form the printing image.
- Mandrel
- A shaft upon which cylinders, or other devices, are mounted or affixed.
- Mask
- An opaque material used to protect open or selected areas of a printing plate during exposure.
- Masking
- Differential exposure of the plate image to balance fine copy with critical reverses or process colour imaging; need for masking is determined by plate exposure latitude.
- Masking Strips
- An opaque material, matted or air channeled surface to allow air to escape. This assists in vacuum drawdown.
- Material Safety
- Data Sheet. See MSDS
- Matte (Dull) Finish
- A finish with low gloss. With respect to coated box paper, a finish with a gloss test less than 55%.
- Micrometer
- An instrument for measurement in terms of minute dimensions,
- Moiré
- An interference pattern caused by the out of register overlap of two or more regular patterns such as dots or lines. In flexographic printing, it can be caused by incorrect relative screen of the anilox rolls and halftone plate. Screen angles are selected to minimize this pattern.
- Monomer
- A chemical combination of molecules corresponding to the individual units of a polymer. It is capable of being incorporated (polymerized) into polymers.
- Mottle
- A speckled, indistinctly spotted, or uneven appearance of printing (as in an ink lay), mostly in solid areas. Attributable to various causes.
- Mounting Equipment
- Device for accurately positioning plates to the plate cylinder.
- Mounting
- The process of affixing plates on a cylinder or base in proper position to register colour to colour as well as to the wrapper or bag to be printed.
- MSDS
- Material safety data sheet. In the United States, OSHA has established guidelines for the descriptive data that should be concisely provided on a data sheet to serve as the basis for written hazard-communication programs. The thrust of the law is to have those who make, distribute, and use hazardous materials be responsible for effective communication.
- Mylar®
- A clear, tough polymeric polyester. Produced in the form of a clear film.
N
- Nanometer
- A unit in which wavelengths of light are expressed. One nanometer is one-billionth of a meter.
- Naphthas
- Alipathic hydrocarbon solvent derived from petroleum such as hexane, V M & P naphtha, etc. Characterized by low K.B. values. Will swell natural or butyl rubber and will have slight effect on Buna-N or Neoprene.
- Negative
- A photographic image of originals on film in reverse from that of the original copy. Dark areas appear light and vice versa.
- Neutral
- The absence of acid or alkaline activity in a material. The presence of an equal concentration of hydrogen and hydroxyl ions. Materials have a pH of 7.
- Nip
- Line of contact between two rolls.
O
- Offset
- The transfer of an improperly or incompletely dried ink from the face of the print to the back of the stock on top of it in the roll or pile. The accidental transfer of ink from the idler or other rolls in a press to the web.
- Opaque
- Impervious to light rays. A paint, exhibiting light obstructive qualities, used to block out areas on a photographic negative not wanted on the plate. To apply opaque materials.
- Organic Solvent
- The medium used to dissolve a substance which contains compounds in the field of chemistry containing carbon.
- Out-Of-Contact
- An air bubble/pocket between the film and plate during exposure. This leaves an unsharp image and/or loss of image detail. Insufficient vacuum or matte level of the film can contribute to this defect.
- Ozone
- A form of oxygen generated by electric motors and corona discharge units which attacks double bonds in photopolymer plates. This causes cracking of the plates and reduces the plate life.
P
- pH Value
- The degree of acidity of alkalinity measured on a scale from 0 to 7 is acid; from 7 to 14 is alkaline, and 7 is neutral. Numerous instruments are available for measuring the pH value.
- Photopolymers
- Generic name for a mixture of materials that can change physical properties (usually harden) on exposure to ultraviolet or visible light.
- Pigment
- Insoluble fine solid particle matter used to give colour, transparency or opacity to inks, paints and plastics.
- Pin Register
- The use of accurately positioned holes and special pins on copy, film, plates, and presses to insure proper register or fit of colours.
- Plate Cylinder
- The cylinder of a press on which the plate is mounted. There are two types of plate cylinder, the Integral, with the shaft a permanent part of the body, and the Demountable, in which the shaft is removable to receive a multiplicity of bodies of varying diameters, and in some cases face widths.
- Polyester Support
- Backing of the plate structure which provides the plate's mechanical strength and dimensional stability. A layer of photopolymer is anchored to this backing.
- Polymer
- A compound reaction in which the molecules of a monomer are linked together to form large molecules whose weight is a multiple of that of the original substance.
- Post Exposure
- UV light exposure of a dried and light finished plate to complete polymerization and attain maximum durability.
- Printing, Flexographic
- The method of direct rotary printing using resilient, raised image printing plates, affixable to plate cylinders of various repeat lengths, inked by a roll or doctor-blade-wiped metering roll, carrying fluid or paste type inks to virtually any substrate.
- Process Colour
- Halftone colour printing created by the colour separation process whereby a piece of copy is broken down to the primary colours - yellow, cyan, magenta plus black - to produce individual halftones. These are recombined at the press to produce the complete range of colours of the original.
- Processing
- Unpolymerized photopolymer material is removed to produce a relief printing plate. A washout solution and brushing action removes the unpolymerized photopolymer which dissolves in the washout solution.
- Process Inks
- A set of transparent inks for high reproduction illustrations by halftone colour separation process. Colours are yellow, magenta, cyan with or without black.
- Process Printing
- The printing from a series of two or more halftone plates to produce intermediate colours and shades.
- Proof
- A prototype of the printed job that is made from plate, film, or electronic data. Used for in-house quality control and/or for customer inspection and approval.
- Proofing Equipment
- Device for obtaining proofs for register and impression, off the press.
R
- Register
- In printing, the fitting of two or more images (usually separate colours) on top of each other in -exact -alignment.
- Release Layer
- A very thin layer between the photopolymer layer and the Mylar coversheet. This layer remains on the surface and minimizes direct contact with the photopolymer. This layer also allows adjustments of the negative prior to exposure. During processing, this layer is removed.
- Relief
- Depth of the image on the plate; the difference between the total plate thickness and the floor thickness.
- Repeat The printing length of a plate cylinder, determined by one revolution of the plate cylinder gear.
- Reproportioning
- See Film Reduction
- Resins Natural or synthetic complex organic substances with no sharp melting point which in solvent solution form the binder portion of the flexographic ink.
- Resolution
- The quantification of printout quality using the number of spots per inch.
- Reverse Printing
- Printing on the underside of a transparent film.
S
- Safe Light
- Light which passes through a filter to screen out rays that are harmful to sensitive material (film, plates, etc.).
- Saturation
- The extreme degree of concentration beyond which a solute can no longer be dissolved into a solvent or, similarly, in which a substance can no longer be absorbed into another medium.
- Screen Angles
- The direction that halftone dots run as a result of screen positioning during the conversion of continuous tone art to halftone film. A set of angles often used are: black 45°, magenta 75°, yellow 90°, cyan 105°.
- Screen Printing
- In flexo, refers to any tone printing work (halftone).
- Screen Ruling
- The number of lines or dots per inch on a halftone screen.
- Screen Sizes
- Designated by the number of halftone dots in one linear inch, or centimeter, of perpendicular or horizontal ruling.
- Separations
- A set of three or four continuous tone or halftone photographic films made photographically or electronically from an original subject. Each film represents one of the printer colours abstracted and are used to make printing plates in colour process printing.
- Shadows
- The darkest area of a reproduction. Represented in a halftone by the largest dots.
- Shelf Life
- The length of time that a container, or a material in a container, will remain in an acceptable condition under specified conditions of storage.
- Shoulder
- A sloping area adjacent to or long the edge of a higher, more prominent, or more important part such as the halftone or line images on the plate surface.
- Solvent
- The medium used to dissolve a substance.
- Specific Gravity
- The ratio of the weight of a body to the weight of an equal volume of water at the same specified temperature.
- Step and Repeat
- The act of or equipment for the positioning and exposing of multiple complete images on film in preparation for plate making.
- Stickyback (U.S)
- Double faced adhesive-coated material used for mounting printing plates to the plate cylinder; may be hard tape or cushion tape. Known elsewhere as 'double-sided tape'
- Still Bottom
- Solid or sludge remaining in the solution recovery unit after the reclamation process. The majority of this sludge is unpolymerized plate material from the processing (washout) process and there remains a minimal amount of solution as well.
- Substrate
- A foundation material on the surface of which a substance may be deposited by printing, coating, etc.
- Swell
- A gradual expansion in thickness of the plate from the original thickness due to the absorption of solvents.
T
- Thick Plates
- See Deep Relief Plates
- Thin Plates
- Plates of thickness 3.175mm/0.125" or less. + 25 micron/1.0 mil is the 3 sigma range for plate to plate uniformity within a production run. The uniformity within a single plate is +12 micron/ 0.5 mil.
- TIR
- Total Indicated Runout refers to the practice of measuring printing cylinders, shafts, anilox rollers, etc., using a dial indicator to identify any variance. Measure variation around a cylinder surface at given locations. Readings are normally taken at the right, left and center of the cylinder, using a dial indicator mounted on a metal base under the cylinder. (Acceptable readings are < 0.0005" for high quality printing.)
- Tone Reproduction
- The relative density of every reproduced tone to the corresponding original density.
- Transfer Roll
- Plain roll rotating in contact with another plain roll transferring variable amounts of ink in and inking system.
- Trapping
- The overlapping of various colours in a design to prevent their separating and not touching as a result of registration variables during printing. Also the condition of printing ink on ink or superimposing one colour on another, in which the first-down ink film is sufficiently dry when the next one is printed over it to properly hide the first down colour.
U
- Ultraviolet (UV) Lights
- Generally fluorescent tubes that emit ultraviolet light rather than normal daylight tubes or incandescent lights
- Undercut
- Engravings on which side-wall areas have been etched under the printing surface. The difference between the radius of the cylinder bearers and the cylinder body, to allow for plate and mounting tape thickness.
- UV Filter
- A transparent material that absorbs light of certain wavelengths to modify the light that reaches sensitized material.
V
- Vehicles
- The liquid component of a printing ink which acts as a carrier for the pigment.
- Viscometer
- Instrument used to measure the viscosity of an ink, varnish or other solution.
- Viscosity
- A broad term encompassing the properties of tack and flow of a liquid, usually ink.
W
- Washout
- See Processing.
- Wavelength
- A quantitative specification of radiant energy. Mathematically, the speed of light divided by the frequency.
- Web
- The paper, foil, film or other flexible material, from a roll, as it moves through the machine in the process of being formed or in the process of being converted, printed, etc.
Y
- Yellow
- One of the subtractive primaries the hue of which is used for one of the 4-colour process inks. It reflects red and green light and absorbs blue light.
Z
- Zahn Cup
- A device for measuring viscosity