GLOSSARY

The terms listed here are selected and defined from the viewpoint of gravure making.
© Taneli Eskola.

A B C D E F G H I J K L M N O P R S T U V W

A

A la poupée
This is the simplest way of making colour prints, by inking the plate with different inks, using fingers or a wad of cotton. Warming the plate will facilitate the blending of inks to achieve a soft gradation of colour.

Acutance
One of the key characteristics when judging the quality of images, acutance indicates the width of the boundary between black and white image areas . It is a central indicator of contrast and exceptionally good in gravure in comparison with other printing processes (cf. definition and resolving power).

Alkaline buffering
A method of treating cardboard and bookbinding materials with calcium carbonate to slow down acidification.

Alternative printmaking processes
The term alternative processes is used for many old photographic methods in which a sensitized emulsion on a paper base darkens and forms an image through a photochemical process. The emulsion was usually sensitized by the photographers themselves. These processes included the platinum and palladium processes, cyanotype, bromoil, carbon, gum and oil printing methods.

Ambient light
Ambient light causes fogging on emulsions, reduced contrast, loss of detail and thereby loss of definition. In gravure work ambient light must be guarded against, especially in the film stage. The ultraviolet wavelengths in ambient light during handling of the polymer plate can cause fogging and significantly reduce the tonal scale of the print.

Antireflex glass
Unreflecting framing glass, which can be used for making a contact print to produce an irregular screen pattern on film.

Aquatint grain
A granular pattern created with rosin or asphaltum dust on a plate, usually in a dusting box, the aquatint grain is necessary for the reproduction of tonal values. It is used in hand-drawn graphic art as well as in photoengraving. Other methods of producing a granular pattern include mezzotint grain and the surface texture of a lithographic stone. A similar pattern can also be produced with an offset plate.

Archive-proof paper
This term is used for all permanent papers, especially cotton-rag writing paper.

Artefact
An object created by an artistic or a design process; a work of art. The question of what constitutes a work of art is a fluid one. To give an example: a gravure print can be considered an original work, but the same print can also be included within the larger context of a portfolio, in which case the portfolio may well be regarded as the art object. The same print can also be a separate framed picture, in which case the picture with its frame is the artefact. Likewise, it is open to question whether individual prints of an edition are different works or versions of one and the same work of art.

Asphaltum
Pitch, bitumen of Judea. An aquatint screen is made by allowing a deposit of fine asphaltum dust or powder to settle on a plate of glass in a dusting box. Coarse asphaltum can be ground finer in a mortar or a food mixer (but remember it is toxic, so the implement should be used for no other purpose). Asphaltum dust is injurious to health also when inhaled, so a respirator mask should always be used when working with it. Instead of asphaltum, an antireflex glass or a stochastic screen can also be used to make the aquatint screen.

Autogravure
A variation of the heliogravure process, common at the turn of the century. The term is derived from Autotype, the name of both a manufacturer and its brand of a pigment paper which was used in autogravure. Sometimes used as a synonym for rotogravure.

B

Bitumen
See asphaltum.

Blankets
Blankets are used between the rollers and the bed of the etching press for the purpose of equalizing the pressure.

Blind print
A proof taken from an uninked plate to determine the pressure on the press that is needed and its equal distribution.

Bookbinder's cloth, book cloth
Cloth which is either lined with paper or impregnated to prevent glue from seeping through. In addition to its aesthetic qualities, cloth should be selected for its durability and should not stretch when damp.

Brayer
An instrument for inking the plate. Brayers used in gravure are usually made from soft rubber. The best quality brayers have a translucent composition roller. Apart from ink, rollers can be used to apply varnish, etc.

Buckram
Stiff, impregnated, coarse cloth used in bookbinding (cf. bookbinder's cloth).

Bulk
The thickness of paper in proportion to its weight. Bulk is proportional to the porosity of the paper, i.e. the amount of air in it. Most printing papers are relatively bulky.

C

Calotype
A print taken from a paper negative on salted paper.

Chiaroscuro
The use of rich tonal variation for artistic effect. Around the turn of the century the development of printing techniques went hand in hand with artistic ideals which emphasized tonality. Printing processes were developed to enable the reproduction of subtle variations of light and shadow in ink on paper. For instance, the way in which paintings, prints and photographs were presented side by side in the journal Camera Work was partly due to a desire to illustrate artistic ideals of tonality through the skilful use of printing techniques (cf. continuous-tone image).

Chinese paper
A soft, weakly sized paper made of bamboo fibre, often sold in rolls. Although of a high quality, Chinese paper is considerably less expensive than Japanese paper.

Collotype
A planographic process in which the printing surface is a glass plate prepared with reticulated gelatine sensitized with potassium dichromate.

Composition roller
A high-class inking roller made from glue and gelatine. Composition rollers are expensive and should be handled with care. They are cleaned with paraffin instead of turpentine, because turpentine makes the material brittle.

Conditioner
Generic term for additives which are used to alter the body and consistency of printing inks.

Consistency
The composition of ink as opposed to its drying or optical qualities. Proper consistency is important to ensure a correct balance between wipeability and tackiness. The wipeability of ink can be improved by adding conditioner, such as Typolin. However, this reduces the stickiness of the ink, which is essential for ensuring the transfer of ink to paper during printing. The plate can be greased with vaseline to aid the lifting of ink from the depressions.

Contact printing
The process of copying an image or pattern from one emulsion to another so that the two emulsions are in contact with each other under a glass plate or in a vacuum frame. Small contact prints can be made without pressure or vacuum. Static electricity can also be used to keep films together.

Contact screen
A screen, for example a gravure screen, on a flexible film for contact printing with a light-sensitive material.

Continuous-tone image
Because of the differences between graphic processes, images are often categorized as either line images, half tone images or continuous-tone images. The latter contain a succession of tonal values forming an unbroken scale of greys.

Continuous-tone film
A low-contrast black-and-white film. It's main use in polymer photogravure is to make a continuous tone image positive to expose the plate.

Contrast
Contrast is the same as difference in density. Perceived contrast is the subjective impression of density differences in an image. The greater the differences, the greater the contrast is perceived to be. To a certain degree, perceived contrast is always affected by the psychological impact on the viewer made by the subject of the image. Contrast can be measured densitometrically to give the density range of the whole picture, or locally as a micro -measurement. Local contrast within a certain area is dependent on the sharpness of contours or acutance in that area. Consequently, the perceived sharpness of the image increases as the contrast increases.

Copperplate printing press
See press.

D

Dabber
A soft hemispherical instrument made of leather or cloth, used for inking the plate.

Dampening
When dampened, paper becomes soft and resilient. This facilitates the transfer of ink from the plate to the paper. The dampness of the paper is one of the central ways of controlling the quality of the print.

Deckle edge
The irregular edge typical of hand-made papers. Genuine deckle edge can be imitated by tearing the paper, preferably when wet, using the edge of a sharp steel ruler.

Definition
A general visual property of images, the product of several different factors which together are perceived as sharpness and tonality. Factors affecting definition include resolving power, acutance, graininess and motif contrast. Definition is the quality of how details, tonality and form are rendered in the image. Because it is a subjective quality which depends on perception, definition can only be evaluated by comparing an image with other images.

Densitometer
A photometric device used to measure density in images and films. Some devices are used to measure reflectivity and some transparency.

Densitometry
Densitometry is the measurement of densities in light-sensitive materials caused by exposure to light and subsequent development. Density is the scientific expression of the darkness in an image. Since the eye adapts to ambient light, density is expressed as a relative value. It is the logarithm of the inverse of transparency.

Depth of field
That area of an image which appears to be in focus, affected by both the aperture and the focal length of the lens. Image sharpness is not absolute but depends on, for instance, magnification and viewing distance. Depth-of-field calculators affixed to lenses should be regarded with scepticism. An image is always sharpest at the point on which the lens is focused, and stopping down increases the depth of the in-focus area only up to a point. In gravure the depth of field occupies a special position, since the impression of softness, of being out of focus, tends to become enhanced in the process.

Digital gravure
A modern gravure method whereby the copperplate is engraved electronically, without the use of a light-sensitive medium to transfer the image to the plate.

Doctor blade
A blade-like steel band used to wipe excess ink from the surface of a rotogravure cylinder.

Double-positive technique
The tonality of a continuous-tone image can be controlled by making two identical image positives with different contrasts. The two positives are registered carefully and the resultant 'sandwich' is used as if it were a single positive film.

Duotone, duogravure, duplex
There are several ways of printing twocolour gravures. Owing to the thickness of the ink deposit in gravure, the plate can be inked with two inks to print warm highlights and cold shadow tones in a single impression. Another method is to apply a thin layer of varnish or transparent ink with a brayer on a wiped plate and then print the plate normally. A third way is to prepare separate plates for each colour and to register these carefully when printing.

Dust grain
See aquatint grain.

Dusting
In copper gravure, the grain resist is created by dusting the plate. In polymer photogravure, the aquatint screen is made by dusting a glass plate with fine asphaltum powder. Dusting takes place in a dusting box, a large swivelled airtight container in which asphaltum dust is disturbed and then allowed to settle on a glass plate placed in the box at the appropriate moment. Since large asphaltum particles come to rest first, the grain will be finer the later the plate is placed in the box, after the large particles have already settled. Dusting can be repeated several times.

E

Edition
The total number of copies of a work printed from a plate. In the context of printmaking the word edition can be misleading, because a single plate may be used to produce a number of different editions.

Embossing
To print a plate without ink is known as blind embossing. A photopolymer plate can also be developed to produce an embossing plate. Because a very deep intaglio is needed for embossing, no screen exposure is made. The embossing pattern can be created by exposing the plate using a high-contrast image positive that has a reduced tonal range. Embossing can be done in an ordinary etching press.

Emulsion
A preparation consisting of two immiscible liquids, one of which is in the form of minute globules dispersed throughout the other. In photography, emulsion is the medium in which the light-sensitive substances of the film are suspended.

Etch, etching
Corroding an image on a plate. A copper plate is etched with acid to produce the intaglio, but the term is not quite appropriate for describing the corresponding process on a polymer plate. Polymer is not etched, it is 'developed' (i.e. it dissolves) in water. Areas hardened under ultraviolet light are insoluble, while unexposed areas are soluble. In photography, etching can also be used to denote the reduction of density (lightening of the image) by chemical means. Cf. Farmer's reducer.

Etching press
See press.

Etching resist
See resist.

Exposure frame, vacuum frame
A device usually consisting of a suction frame, light source and a timing unit. The exposure frame is used to expose the polymer plate with the image positive. When purchasing an exposure frame the important things to consider are the strength and smoothness of the suction, the strength and evenness of the ultraviolet light source and the reliability of the timer.

F

Farmer's reducer
Farmer's reducer is made from highly toxic potassium ferric cyanide. Together with a fixing agent, Farmer's reducer is used to remove silver bromide from emulsions, i.e. to reduce density. Farmer's reducer removes silver from the emulsion evenly throughout, regardless of density.

Ferric chloride
FeCl3 • 6H2O. A chemical substance used to etch coppergravure plates.

Flexography
The most common use of polymer plates is in flexography, which is a form of high-speed rotogravure used to print on uneven and non-absorbent surfaces.

Fogging
A tone caused by ambient light. Overage photographic materials often manifest fogging.

Full-scale image
A continuous-tone image containing tones from the deepest black to the brightest highlight.

G

Gelatine
Gelatine is a glue-like substance derived by boiling the ligaments, bones, etc. of animals. It is used as a vehicle in photographic emulsions.

Gelatine paper
See pigment paper.

Grain
A cluster of silver halide crystals, the basic physical element of density in a photograph.

Grain gravure
A gravure process using a screen composed of a grain pattern, which is not necessarily visible in the final print.

Graphic arts film
Usually a high-contrast lith film, but can also be a low-contrast continuous-tone film. Lith films are used in gravure for making image positives from line drawings, for text or for the high-contrast second film in the doublepositive technique. When developed with a graphic developer, these films display an extreme contrast, with only black and white remaining in the image, but with a soft developer and shorter exposure time contrast can be reduced. This can be used to control the contrast of the second positive in the double-positive technique to prevent the formation of tonal breaks.

Graphics
(from Gr. grafein, meaning to engrave, draw.) Generic term used to denote the various drawing and printing arts. Printmaking methods are divided according to technique into letterpress (e.g. autotype), intaglio (of which gravure is one) and planographic processes (e.g. offset) The most orthodox graphic artists still insist that the printing plates used for art graphics must be drawn by hand.

Gravure
An engraving. Hand-drawn gravure processes include copper engraving and drypoint. Photographic gravure processes include photoetching, heliogravure, rotogravure and polymer gravure.

Gravure screen
Because the tonal values in a gravure print are primarily the result of differences in the thickness of the ink layer, the gravure screen works on a different principle than e.g. offset screen, in which the screen transforms the tones in the image into a mosaic of completely black or white areas. The gravure screen forms on the plate a pattern of lands, or ridges, which holds the ink in place. This pattern is called the resist. In hand-printed gravure an irregular aquatint screen is used; in rotogravure the screen is usually a mechanical, lined regular screen. Because of the thickness of the ink and the growing of the dot on the paper, the print does not make a mechanical impression. (Cf. stochastic screen, resist.)

Grinding
Inks can be made from pigment and oils by mixing them on e.g. a glass plate and then grinding them to a smooth consistency.

H

Halftone
An image seeking to imitate a continuous-tone image with the use of black and white dots, which to the naked eye seem to form continuous grey tones. Halftone screens are used in e.g. offset printing. The photogravure method reproduces real continuous tones.

Hardening
An emulsion can be hardened by the addition of alum, especially to the fixing bath. A hardening fixing agent makes reducing and toning a film more difficult.

Heliography
A generic term for the experiments in intaglio printing started by Nicéphore Niépce as early as 1813, and resulting in permanent photographic images by the year 1822.

Heliogravure
(from Gr. helio, meaning the sun, and Fr. gravure, meaning to engrave.) A photographic engraving process. Nicéphore Niépce had already experimented with heliography in the 1810s, but the first usable heliogravures did not appear until the 1850s. The method was perfected in the 1880s by Karl Klic, who transferred the image with the use of a gelatine paper onto a copper plate dusted with asphaltum.

High key
The light tones in an image. In a high key image highlights dominate (cf. low key).

Highlights
The lightest areas of an image; also used for the reflection of a light source on a shiny object. Highlights play a central role in creating the appearance of brightness in a continuous tone image. Preserving the purity of highlights in the printed image is one of the marks of true craftsmanship in gravure work.

Hollow
The (etched) hollow is the basis of the entire intaglio process. Its form is the result of the exposures using the image positive and the contact screen. The deeper the hollow, the more ink is transferred to paper and the darker that area appears in the print. An ideal hollow has very steep walls to hold the ink firmly during wiping. In exposing and etching a plate, the aim is usually to obtain hollows that are as deep as possible. (Cf. intaglio.)

Hotplate
An heating plate used to heat the printing plate. Heating an inked plate makes the ink more flexible and facilitates wiping. The printing properties of the ink may also improve with heating.

I

Ingres paper
Also called Paris paper, Ingres paper is named after the French painter J.A.D. Ingres. It is a coarse, often tinted paper used in bookbinding as lining paper.

Ink
Etching inks are very sticky, oil-based inks. About 90% of the pigments used in them are organic products of the petrochemical industry. Inorganic pigments include various oxides such as ochre, sienna and umber. Etching inks contain 20% of pigments, about 30% of vehicles (oils, varnishes or resins), about 45% of solvents and conditioners (silicates affecting viscosity and stickiness), and about 5% of siccatives (drying agents) and antioxidants (substances to prevent the ink from drying in the tin). Most inks are light fast, i.e. they do not bleach in light. An etching ink can be tinted by adding small amounts of artist's oil paint or lithographic or offset ink, without affecting the quality of the ink. If colour is added to the ink, no additional oil is needed. The best oil colours for tinting are translucent, rich oils which do not contain white pigment (viridian, alizarin crimson, Prussian blue, etc.).

Ink resist
See resist.

Intaglio
Literally, "to engrave below the surface". Intaglio is a generic term for those printing processes in which the image is hollowed into the printing surface. In addition to gravure, intaglio methods include many metal-engraving techniques such as etching, aquatint and mezzotint. The intaglio surface can be a plate or a cylinder. The term intaglio is also used to denote the etched pattern itself.

J

Japanese paper
A paper consisting of very long and thick fibres, which make the paper very strong and gives it a beautiful decorative texture. Japanese paper occupies a special place in gravure, because in the late 19th century heliogravures were often printed – in the spirit of Japonism – on thin Japanese paper which was then mounted on thicker etching paper. Japanese paper is also an excellent material to use as protective leaves in portfolios and for textual graphic elements.

K

Kerosene
A solvent with a somewhat slower evaporation rate than turpentine. Because kerosene also penetrates rubber it is used for cleaning composition rollers.

L

Letterpress
One of the basic methods of printmaking, along with the intaglio and planographic processes, in which the raised areas of the plate comprise the printing surface. The photopolymer plate was originally designed for letterpress printing. If the polymer plate is used for embossing, the thickness of the polymer coating is an essential factor, where the indentation must be as deep as possible. The photographic process does not limit the shape of the relief in any way.

Line copy
An image consisting only of black and white with no intermediate tones.

Line graphics
Graphic methods based on the use of line, such as copper engraving, steel engraving, drypoint and line etching. Tonal graphics can be regarded as the opposite to line graphics in that they use surfaces of differing tonality. The latter methods include aquatint, mezzotint, autotype and gravure.

Linseed oil
Oil obtained by pressing flax seeds. Raw or cold-pressed linseed oil is the best for artistic purposes. Linseed oil is a basic ingredient in many printing inks.

Low key
The dark end of the tonal scale. In a lowkey image the picture is dominated by shadows. Low-key images are best suited for gravure work (cf. high key).

M

Masking
The edges of the polymer plate can be masked during printing. Masking is an easy way of ensuring a clean plate mark. In copperplate gravure no mask is needed, because the edges of the plate are usually polished and are thus easy to wipe clean.

Master screen
A glass plate with a fired pattern of fine asphaltum dust on it. A film screen is a contact copy of the master screen.

Mastic
The resin of a small evergreen tree, Pistacia Lentiscus, used in an alcohol solution as varnish to increase the density of gravures and create a protective film of resin over the easily scratched ink surface. Castor oil can be added to the varnish to reduce the brittleness of mastic. Paul Strand sprayed mastic on the gravures of his Photographs of Mexico portfolio.

Mezzogravure
A turn-of-the-century gravure process in which excess ink was wiped from the plate by a mechanical blade, but where the plate had an aquatint grain.

Mezzotint screen
See screen.

Mid-grey
A grey tone which reflects 18% of incident light. Grey wedges are based on the mid-grey tone.

Mid-tones
The grey tones in the middle of the tonal scale.

N

Negative
An image with inverted densities. Since gravure is a positive method, a negative image is the most natural starting point for the process. The quality of the original negative is preserved best when the intermediate steps in making the continuous-tone image positive are reduced to a minimum.

Newton rings
An interference pattern created at the meeting point of two refracting surfaces. When exposing a polymer plate in a vacuum frame, the even distribution of pressure can be controlled by watching the Newton rings. When the vacuum is evenly distributed throughout the frame, the entire plate is covered with tiny Newton rings.

Neogravure
A seldom used term which refers to new photogravure processes as opposed to traditional processes.

O

Offset
See planography.

Opaque white
An opaque white printing ink as opposed to translucent white ink (cf. printing oil, Typolcreme, Typolin).

Original
In gravure the term usually refers to a negative taken with a camera.

Original print
The question of original prints is somewhat complex in connection with photogravure. Artists like to define original prints as those taken from a plate made by the artist him or herself, in which the method of printing brings out the inherent qualities of the work. Gravure falls naturally within the scope of this definition, because it aims to reproduce photographic qualities with those very graphic means that lend themselves best to the aims of the artist photographer. In most cases, the gravure-maker is responsible for creating the photograph, the plate as well as the print. In such a case the gravure is an original print made with the technique which is best suited to that particular image. However, the most orthodox artists preclude gravure from graphic art as a form of reproductive graphics.

Ortochromatic
A black-and-white photographic emulsion sensitive to blue-green light. Orthochromatic film can be handled under a red safety light.

Overexposure
Overexposing the continuous-tone film gives too dense an image positive. The overexposure can be compensated for by increasing plate exposure time. Since the polymer plate produces a positive image, overexposure results in a print that is too light and has insufficient contrast. Overexposure with the aquatint screen also reduces contrast and tonality.

P

Panchromatic
A black-and-white emulsion that is equally sensitive to all wavelengths of visible light. Used in gravure when a true positive copy is made of a colour negative.

Paper
(from Gr. papyros, meaning papyrus, a type of reed.) Thin, pliable sheets of material made by filtering, couching, pressing and drying pulped vegetable fibre. According to one definition, the cut-off point between paper and cardboard is 150 grams per square metre, but material weighing as much as 250 g/sq.m. is still flexible enough to feel like paper, especially in larger sheets.

Photoetching
An intaglio image printed from a plate on which the depth of the etch is constant. Tonality is controlled through the size of the dots, as in offset.

Photogramme
An image exposed directly on a lightsensitive film without the use of a camera. In gravure photogrammes are very rare, but there is nothing to prevent you from making them.

Photogravure
See gravure.

Photomechanical printing
A printing process utilizing lightsensitive materials. Nowadays the term is used to denote those printing methods which contain a photographic element: autotype, phototype, photolithography, heliogravure, rotogravure, Collotype, Woodburytype, offset and certain forms of silk screen.

Photopolymer plate
See pp. 53-58.

Pigment
(from L. pingere, meaning to colour.) Fine coloured powder mixed with a vehicle to make printing inks. Pigment is insoluble in the vehicle.

Pigment paper, gelatine paper
A film or paper coated with dyed gelatine. Pigment paper sensitized with potassium or ammonium carbonate played a central role in the development of gravure processes after 1855. A layer of gelatine (etching resist) was transferred to the surface of a copper plate. The varying thickness of the gelatine controlled the etching speed and thus the depth of the bite. The gelatine etch resist was the basis for halftone etching for more than 100 years.

Planography
A generic term for all the techniques which involve a plane surface for printing. The first planographic method was lithography. Offset, which was developed from lithography at the beginning of the 20th century, is the dominant book printing method today. Along with photolithography, Collotype was one of the first planographic methods with which it was possible to print continuous-tone images in the 1860s.

Plate mark
The indentation made by a printing plate in the paper. One of the distinguishing characteristics of all gravure and intaglio work, the plate mark is also a beautiful way of setting off the printed area from the rest of the paper. The greater the pressure used in the press, the smoother and more compact the plate mark. The plate can be cut off directly from the edge of the image area, or a white margin can be left. (Cf. masking.)

Plate tone
A thin layer of ink spread on the plate with the palm of the hand to give texture to highlights. Plate tone can also be the unintended, dirty texture of highlights.

Platinum printing
A printing process in which a paper sensitized with iron darkens under light because of the activity of platinum salts.

Polymerization
The composition of long chains of molecules called polymers from shorter chains called monomers. A photopolymer hardens when exposed to ultraviolet light. Printing inks also dry by polymerizing.

Portfolio
(from It./L. portare, meaning to carry, and folia, meaning leaves.) A collection of prints. Gravures are especially suited to composing portfolios or other kinds of artistic books.

Press, etching press, copperplate printing press
The device used for printing gravures. Technological advances have removed intaglio processes from the mainstream of printing and have thus resulted in a standstill in the development of the etching press. The etching press used today is the same kind of heavy construction which has been in use for centuries. An electrically operated press is best for the smooth movement of the bed through the rollers, but in some models the motor is not powerful enough to ensure smooth movement over the plate when a lot of pressure is used. The greater the diameter and weight of the upper roller, the more easily it moves over a plate, even a large one. A roller that is too small will "push" the plate a few millimetres before rolling over it. It is important that the surface of the rollers is smooth. The tiniest dents and bumps will show up in the print. To prevent accidents, the operating switch of an electrical press should be such that it can only be turned with both hands. Another danger is driving the bed too far so that it drops on the floor or scratches the rollers.

Pressure
Pressure is a crucial factor in transferring ink from the plate to paper. Pressure must be sufficient and equally distributed. The dryer, thicker and coarser the paper, the greater the pressure must be to make a high-quality print. Under pressure, the paper is smoothed and compacted throughout the plate mark.

Print
Prints can be either (I) ink on paper, such as etching, woodcut or gravure, or (2) photographic prints made on lightsensitive material.

Printing oil
The oil used in printmaking is copperplate oil or stand oil. It is refined from linseed oil. Plate oil is added one drop at a time to the ink to increase wipeability.

Proof
Proofs are trial prints made to test the properties of the plate.

R

Rag paper
High-quality paper usually made from pure cotton rag. The long cotton fibres ensure the durability of the paper, but they also impart flexibility and softness to it. Because rag papers have a neutral pH (balance of acidity and alkalinity) they are also very permanent. Etching papers are almost invariably made from pure rag.

Reducing
See Farmer's reducer.

Registration
The precise positioning of paper on a printing plate. Registration is important in the double-positive technique and in printing with more than one plate.

Resist, etching resist, ink resist
In intaglio, the hollows on the plate are filled with ink. When excess ink is wiped from the plate, the ink remaining in the depressions must remain in place. This is achieved because of the resist, which is created by exposing the plate through a screen. In polymer gravure, the resist is created using ultraviolet light and an aquatint screen. Areas which have received ultraviolet light become hardened and remain raised after the plate is developed. In the final print the resist is undetectable owing to the definition of the image and the spreading of ink on paper

Resolving power
The shortest possible distance at which two points can still be separated from one another on a photographic medium. In other words, resolving power is a measure of the capacity of the process to reproduce fine details (cf. acutance and definition).

Reticulation
(from L. rete, meaning a net.) A net-like pattern. Reticulation of the gelatine is produced when the temperature of the emulsion is lowered quickly, which causes the emulsion to shrink and crack, resulting in an irregular pattern. Reticulation is used in e.g. collotype. In polymer photogravure, contact failure caused by insufficient suction can cause a similar fault.

Retouching
Retouching means correcting an image by removing defects, in both the negative and the positive stages. Continuous-tone films are difficult to retouch because of the accumulation of contrast: corrections and alterations made on the low-contrast film become enhanced and show up in the print as darker than their surroundings. Light spots should be retouched on the final gravure, using colours.

Retroussage
Increasing the richness of tones by drawing the ink from the hollows by carefully rubbing an inked and wiped plate with a piece of cloth or felt.

Rotogravure
A rotary printing process originally invented by Eduard Mertens at the beginning of the 20th century. In rotogravure the image is etched on a copper cylinder and printed on a continuous paper roll. Mertens' invention speeded the manual heliogravure process by mechanizing the wiping stage. This could only be done by replacing the granular, dusted resist with a regular lined screen pattern to create a steep cell structure which was capable of holding runnier inks. Today rotogravure is commonly used for printing periodicals and advertisements.

S

Screen
The pattern which enables the reproduction of tones on a printing plate. The dots of an offset screen become lighter towards the edges, whereas in gravure a hard-dot screen is used to create the resist. Different screens used in graphic art include the grain, irregular, sand, aquatint and mezzotint screens.

Screen gravure
A gravure made using a screen with a regular pattern.

Sensitometry
The study of the light-sensitivity of emulsions.

Set-off
The unintended transfer of ink from one sheet to an adjacent sheet. Smudging the back of prints can be prevented by drying the prints thoroughly in a special frame so that they don't come into contact with each other, or by using protective sheets between the prints.

Sheet-fed gravure
A hand-wiped gravure printed in an etching press, usually made using a grain screen.

Siccative
A drying agent. Etching inks contain very small amounts of siccatives, because there is seldom any harm in slow drying. Siccatives are chiefly added to slowdrying linseed oil-based inks. They are often salts of cobalt.

Stochastic screen
A digitally produced, frequencymodulated irregular screen pattern which can be used to make the resist (cf. aquatint grain, screen, resist).

T

Tackiness
That property of ink which makes it cling to the plate. The tackier the ink used in gravure work, the darker the resultant print, but a tacky ink can also be difficult to wipe. Conditioners such as Typolin can be used to reduce the tackiness.

Tactile, tactility
(from L. tangere, meaning to touch.) Pertaining to the sense of touch. Gravures make a very strong tactile impression, because the rag paper used in printing is pleasant to the touch and gives the image a velvety, rich matte surface.

Tarlatan
A gauze cloth used in intaglio work.

Tearing
When the ink is not transferred from the hollows to the paper but results in spots or a broken and irregular impression, we speak of tearing. At worst, tearing can cause cracks in the surface of the paper, or the entire surface of the paper may adhere to the plate.

Texture
The visual rendering of the tactile or physical quality of the subject of an image. Materials used in printing have their own texture, which in print merges with the texture of the image. Gravure has a very active, tactile texture.

Tonal break
An unintentional break or jump along an outline, caused by an insufficient tonal range. One of the advantages of the gravure process as opposed to e.g. polychrome offset is that it has a relatively straight D log E curve which prevents the formation of tonal breaks. In copperplate gravure tonal breaks can be caused by faulty etching. Also in the double-positive technique, a tonal break can be created if the tonal range of the second, high-contrast positive begins too abruptly.

Tonal printing processes
Those printing processes which enable the reproduction of continuous tones. These processes include gravure, intaglio, offset and lithography. The separation of these processes from those which use surfaces of uniform tonality is somewhat artificial, since methods like woodcut or silk screen can be used to reproduce very subtle tonal differences. P. H. Emerson divided printing processes into line and tonal processes, and he emphasized the possibilities of the latter in art printing.

Tonal range, tonal scale
The entire range of tonal differences. In filmwork, the maximum tonal range when working with polymer plate should be about D. 1. 5 for all details to be reproduced in the final print. Each image also has its own tonal scale.

Tonal rendering
The translation of the patterns of light and dark in the subject into the tonal range of an image.

Tone, tonal value
As a density value, tone is the same as an area with a uniform density. Tones in an image reflect the variation of light and shade in the subject.

Toning
This term is generally used in connection with the chemical alteration of the hue of the emulsion in black-and-white photographs.

Transparent white ink
An additive used to reduce the opacity of the ink, especially in the highlights.

Turpentine
The name for a class of liquids composed of oleoresins. French turpentine is distilled from the resinous pitch obtained from conifers of the Mediterranean region; Venetian turpentine from that of larch trees. French turpentine is also called oil of turpentine. The cheapest varieties of mineral turpentine are by-products of the petrochemical industry. (Cf. white spirit.)

Typolin, Typolcreme
A popular conditioner, used to make tacky inks easier to wipe.

U

Undercut
An overdeveloped, unstructured hollow incapable of holding ink. If undercuts develop on the plate, image exposure or screen exposure time or both must be increased. If this does not help, a lighter image positive must be made.

Underexposure
Underexposing negative material results in insufficient density and the loss of tonality, especially at the low end of the tonal scale. In a polymer plate, which functions on a positive-to-positive principle, underexposure results in an overdeveloped, dark plate, on which the shadows are mere unstructured hollows.

V

Vacuum frame
See exposure frame.

Varnish
A preparation containing resinous matter dissolved in oil or alcohol. A thin coat of varnish on a print becomes oxidized and forms a film over the surface. Gravures can be varnished to deepen the density of the image and increase gloss. Offset varnishes, mastic and dammar, can be used either sprayed or rolled. The plate mark can be masked with masking paper so that the varnish is applied only to the image area. Varnish can be tinted with coloured inks.

Vehicle
The liquid, usually oil, with which pigments are mixed to produce ink.

W

White spirit, turpentine substitute
A liquid manufactured by distilling petroleum, used as a solvent, thinner and cleaning agent. Polymer plates can be cleaned with white spirit, but it cannot be used for thinning ink.

Whiting
Fine powdered chalk used to facilitate hand-wiping and to brighten highlights.

Woodburytype
A printing process, used mainly in the 19th century, in which a mixture of pigment and gelatine was transferred under pressure from a lead mould onto paper.