Printmaking is the process of creating artworks by printing on paper. Printmaking covers only the process of creating prints that have an element of originality, rather than just being a photographic reproduction of a painting. Except in the case of monotyping, the process is capable of producing multiples of the same piece, called a print; each print produced is not considered a "copy" but rather is considered an "original". This is because each print varies to an extent due to variables intrinsic to the printmaking process, because the imagery of a print is not a reproduction of another work but rather is a unique image designed from the start to be expressed in a particular printmaking technique. A print may be known as an impression. Printmaking is not chosen only for its ability to produce multiple impressions, but rather for the unique qualities that each of the printmaking processes lends itself to. Prints are created by transferring ink from a matrix or through a prepared screen to a sheet of paper or other material.
Common types of matrices include: metal plates copper or zinc, or polymer plates for engraving or etching. Screens made of silk or synthetic fabrics are used for the screenprinting process. Other types of matrix substrates and related processes are discussed below. Multiple impressions printed from the same matrix form an edition. Since the late 19th century, artists have signed individual impressions from an edition and number the impressions to form a limited edition. Prints may be printed in book form, such as illustrated books or artist's books. Printmaking techniques are divided into the following basic categories: Relief, where ink is applied to the original surface of the matrix. Relief techniques include woodcut or woodblock as the Asian forms are known, wood engraving and metalcut. Intaglio, where ink is applied beneath the original surface of the matrix. Intaglio techniques include engraving, mezzotint, aquatint. Planographic, where the matrix retains its original surface, but is specially prepared and/or inked to allow for the transfer of the image.
Planographic techniques include lithography and digital techniques. Stencil, where ink or paint is pressed through a prepared screen, including screenprinting and pochoir. Other types of printmaking techniques outside these groups include collagraphy and viscosity printing. Collagraphy is a printmaking technique; this texture is transferred to the paper during the printing process. Contemporary printmaking may include digital printing, photographic mediums, or a combination of digital and traditional processes. Many of these techniques can be combined within the same family. For example, Rembrandt's prints are referred to as "etchings" for convenience, but often include work in engraving and drypoint as well, sometimes have no etching at all. Woodcut, a type of relief print, is the earliest printmaking technique, the only one traditionally used in the Far East, it was first developed as a means of printing patterns on cloth, by the 5th century was used in China for printing text and images on paper.
Woodcuts of images on paper developed around 1400 in Japan, later in Europe. These are the two areas where woodcut has been most extensively used purely as a process for making images without text; the artist draws a design on a plank of wood, or on paper, transferred to the wood. Traditionally the artist handed the work to a specialist cutter, who uses sharp tools to carve away the parts of the block that will not receive ink; the surface of the block is inked with the use of a brayer, a sheet of paper slightly damp, is placed over the block. The block is rubbed with a baren or spoon, or is run through a printing press. If in color, separate blocks can be used for each color, or a technique called reduction printing can be used. Reduction printing is a name used to describe the process of using one block to print several layers of color on one print; this involves cutting a small amount of the block away, printing the block many times over on different sheets before washing the block, cutting more away and printing the next color on top.
This allows the previous color to show through. This process can be repeated many times over; the advantages of this process is that only one block is needed, that different components of an intricate design will line up perfectly. The disadvantage is. Another variation of woodcut printmaking is the cukil technique, made famous by the Taring Padi underground community in Java, Indonesia. Taring Padi Posters resemble intricately printed cartoon posters embedded with political messages. Images—usually resembling a visually complex scenario—are carved unto a wooden surface called cukilan smothered with printer's ink before pressing it unto media such as paper or canvas; the process was developed in Germany in the 1430s from the engraving used by goldsmiths to decorate metalwork. Engravers use a hardened steel tool called a burin to cut the design into the surface of a metal plate, traditionally made of copper. Engraving using a burin is a difficult skill to learn. Gravers come in a variety of sizes that yield different line types.
The burin produces a unique and recognizable quality of line, characterized by
Tinctures constitute the limited palette of colours and patterns used in heraldry. The need to define and blazon the various tinctures is one of the most important aspects of heraldic art and design; the use of these tinctures dates back to the formative period of European heraldry, in the twelfth and thirteenth centuries, but the range of tinctures and the manner of depicting and describing them has evolved over time, as new variations and practices have developed. The basic scheme and rules of applying the heraldic tinctures dates to the formative period of heraldry, during the twelfth and thirteenth centuries. By the time of the earliest coloured heraldic illustrations, in the mid-thirteenth century, the use of two metals, five colours, two furs had become standardized, since that time, the great majority of heraldic art has employed these nine tinctures. Over time, variations on these basic tinctures were developed with respect to the furs, although the authorities differ as to whether these should be considered separate tinctures, or varieties of existing ones.
Two additional colours appeared, were accepted by heraldic writers, although they remained scarce, were termed stains, from the belief that they were used to signify some dishonour on the part of the bearer. The practice of depicting certain charges as they appear in nature, termed proper, was established by the seventeenth century. Other colours have appeared since the eighteenth century in continental heraldry, but their use is infrequent, they have never been regarded as heraldic, or numbered among the tinctures that form the basis of heraldic design; the frequency with which different tinctures have been used over time has been much observed, but little studied. There are, some general trends of note, both with respect to the passage of time, noted preferences from one region to another. In medieval heraldry, gules was by far the most common tincture, followed by the metals argent and or, at least one of which appeared on the majority of arms. Among the colours, sable was the second most common, followed by azure.
Over time, the popularity of azure increased above that of sable, while gules, still the most common, became less dominant. A survey of French arms granted during the seventeenth century reveals a distinct split between the trends for the arms granted to nobles and commoners. Among nobles, gules remained the most common tincture followed by or by argent and azure at nearly equal levels. Among commoners, azure was the most common tincture, followed by or, only by gules and sable, used more by commoners than among the nobility. Purpure is so scarce in French heraldry that some authorities do not regard it as a "real heraldic tincture". On the whole, French heraldry is known for its use of azure and or, while English heraldry is characterized by heavy use of gules and argent, unlike French heraldry, it has always made regular use of vert, occasional, if not extensive, use of purpure. German heraldry is known for its extensive use of or and sable. German and Nordic heraldry make use of purpure or ermine, except in mantling and the lining of crowns and caps.
In fact, furs occur infrequently in Nordic heraldry. The colours and patterns of the heraldic palette are divided into three groups known as metals and furs; the metals are or and argent, representing gold and silver although in practice they are depicted as yellow and white. Or derives its name from the Latin aurum, "gold", it may be depicted using either metallic gold, at the artist's discretion. Argent is derived from the Latin argentum, "silver". Although sometimes depicted as metallic silver or faint grey, it is more represented by white, in part because of the tendency for silver paint to oxidize and darken over time, in part because of the pleasing effect of white against a contrasting colour. Notwithstanding the widespread use of white for argent, some heraldic authorities have suggested the existence of white as a distinct heraldic colour. Five colours have been recognized since the earliest days of heraldry; these are: red. Gules is of uncertain derivation. Sable is named for a type of marten, known for its luxuriant fur.
Azure comes through the Arabic lāzaward, from the Persian lāžavard both referring to the blue mineral lapis lazuli, used to produce blue pigments. Vert is from Latin viridis, "green"; the alternative name in French, sinople, is derived from the ancient city of Sinope in Asia Minor, famous for its pigments. Purpure is in turn from Greek porphyra, the dye known as Tyrian purple; this expensive dye, known from antiquity, produced a much redder purple than the modern heraldic colour. As a heraldic colour, purpure may have originated as a variation of gules. Two more were acknowledged by most heraldic authoriti
A dip pen or nib pen consists of a metal nib with capillary channels like those of fountain-pen nibs, mounted in a handle or holder made of wood. Other materials can be used for the holder, including bone and plastic. Dip pens have no ink reservoir, so the user must recharge the ink from an ink bowl or bottle to continue drawing or writing. There are simple, tiny tubular reservoirs that illustrators sometimes clip onto dip pens, which allow drawing for several minutes without recharging the nib. Recharging can be done by dipping into an inkwell, but it is possible to charge the pen with an eyedropper, a syringe, or a brush, which gives more control over the amount of ink applied. Thus, "dip pens" are not dipped. Dip pens emerged in the early 19th century, when they replaced quill pens and, in some parts of the world, reed pens. Dip pens were used before the development of fountain pens in the 19th century, are now used in illustration and comics; the dip pen has certain advantages over a fountain pen.
It can use waterproof, particle-and-binder-based inks, such as India ink, drawing ink, acrylic inks—each of which would destroy a fountain pen by clogging it—and the traditional iron gall ink, which can corrode fountain pens. Dip pens are more sensitive to variations of pressure and speed, producing a line that varies in thickness. There is a wide range of exchangeable nibs for dip pens, so different types of lines and effects can be created; the nibs and handles are far cheaper than most fountain pens, allow color changes much more easily. The earliest known split-nib metal dip pen is a surviving copper-alloy pen found in Roman Britain. Several other surviving all-metal and removable-nib pens from the Middle Ages and Renaissance have been found, suggesting they were used alongside quill pens; the steel pen is first attested in Daniel Defoe's book "A Tour Through the Whole Island of Great Britain – 1724–26". In Letter VII Defoe wrote: "the plaster of the ceilings and walls in some rooms is so fine, so firm, so entire, that they break it off in large flakes, it will bear writing on it with a pencil or steel pen."
In Newhall Street, John Mitchell pioneered mass production of steel pens in 1822. His brother William Mitchell set up his own pen making business in St Paul's square; the Mitchell family is credited as being the first manufacturers to use machines to cut pen nibs, which sped up the process. The Jewellery Quarter and surrounding area of Birmingham, England was home to many of the first dip pen manufacturers, which some companies establishing there to produce pens; some of those companies were Sir Josiah Mason, Hink Wells & Co.. Baker and Finnemore, C. Brandauer & Co. D. Leonardt & Co.. Baker and Finnemore operated near St Paul's Square. C Brandauer & Co Ltd. founded as Ash & Petit, traded at 70 Navigation Street. Joseph Gillott & Sons Ltd. made pen nibs in Bread Street, now Cornwall Street. Hinks Wells & Co. traded in Buckingham Street, Geo W Hughes traded in St Paul's Square, D. Leonardt & Co./Leonardt & Catwinkle traded in George Street and Charlotte Street, M Myers & Son. were based at 8 Newhall Street.
By 1830 John and William Mitchell, Joseph Gillott, Josiah Mason were the major manufacturers in Birmingham. In Germany the industrial production of dip pens started in 1842 at the factory of Heintze & Blanckertz in Berlin. By the 1850s, Birmingham existed as a world centre for steel nib manufacture. More than half the steel nib. Thousands of skilled craftsmen and women were employed in the industry. Many new manufacturing techniques were perfected in Birmingham, enabling the city's factories to mass-produce their pens cheaply and efficiently; these were sold worldwide to many who could not afford to write, which encouraged the development of education and literacy. By 1860 there were about 100 companies making steel nibs in Birmingham, but 12 large firms dominated the trade. In 1870 Mason, Sommerville and Perry, merged to form Perry & Co. Ltd. which became one of the largest manufacturers in the world, with near 2,000 employees. Richard Esterbrook manufactured quill pens in Cornwall. In the 19th century, he saw a gap in the American market for steel nib pens.
Esterbrook approached five craftsmen who worked for John Mitchell in Navigation Street with a view to setting up business in Camden, New Jersey, US. Esterbrook founded his company in 1858, it grew to become one of the largest steel pen manufacturers in the world. In 1971 it went out of business; the oblique dip pen was designed for writing the pointed pen styles of the mid 19th to the early 20th century such as Spencerian Script, although oblique pen holders can be used for earlier styles of pointed penmanship such as the copperplate scripts of the 18th and 19th centuries. As the name suggests, the nib holder holds the nib at an oblique angle of around 55° pointing to the right hand side of the penman; this feature helps in achieving the steep angle required for writing certain scripts, but more it prevents the right hand nib tine from dragging on the paper as can be experienced when using a straight nib holder with a straight nib for this purpose. The decreasing production of dip pens and the subsequent demise of the industry in Birmingham is blamed on the invention of the ballpoint pen in 1938 by the Hungarian Laszlo Biro.
The egg is the organic vessel containing the zygote in which an embryo develops until it can survive on its own. An egg results from fertilization of an egg cell. Most arthropods and mollusks lay eggs, although some, such as scorpions do not. Reptile eggs, bird eggs, monotreme eggs are laid out of water, are surrounded by a protective shell, either flexible or inflexible. Eggs laid on land or in nests are kept within a warm and favorable temperature range while the embryo grows; when the embryo is adequately developed it hatches, i.e. breaks out of the egg's shell. Some embryos have a temporary egg tooth they use to pip, or break the eggshell or covering; the largest recorded egg is from a whale shark, was 30 cm × 14 cm × 9 cm in size. Whale shark eggs hatch within the mother. At 1.5 kg and up to 17.8 cm × 14 cm, the ostrich egg is the largest egg of any living bird, though the extinct elephant bird and some dinosaurs laid larger eggs. The bee hummingbird produces the smallest known bird egg; some eggs laid by reptiles and most fish, amphibians and other invertebrates can be smaller.
Reproductive structures similar to the egg in other kingdoms are termed "spores," or in spermatophytes "seeds," or in gametophytes "egg cells". Several major groups of animals have distinguishable eggs; the most common reproductive strategy for fish is known as oviparity, in which the female lays undeveloped eggs that are externally fertilized by a male. Large numbers of eggs are laid at one time and the eggs are left to develop without parental care; when the larvae hatch from the egg, they carry the remains of the yolk in a yolk sac which continues to nourish the larvae for a few days as they learn how to swim. Once the yolk is consumed, there is a critical point after which they must learn how to hunt and feed or they will die. A few fish, notably the rays and most sharks use ovoviviparity in which the eggs are fertilized and develop internally; however the larvae still grow inside the egg consuming the egg's yolk and without any direct nourishment from the mother. The mother gives birth to mature young.
In certain instances, the physically most developed offspring will devour its smaller siblings for further nutrition while still within the mother's body. This is known as intrauterine cannibalism. In certain scenarios, some fish such as the hammerhead shark and reef shark are viviparous, with the egg being fertilized and developed internally, but with the mother providing direct nourishment; the eggs of fish and amphibians are jellylike. Cartilagenous fish eggs are fertilized internally and exhibit a wide variety of both internal and external embryonic development. Most fish species spawn eggs that are fertilized externally with the male inseminating the eggs after the female lays them; these eggs would dry out in the air. Air-breathing amphibians lay their eggs in water, or in protective foam as with the Coast foam-nest treefrog, Chiromantis xerampelina. Bird eggs are incubated for a time that varies according to the species. Average clutch sizes range from one to about 17; some birds lay eggs when not fertilized.
The default color of vertebrate eggs is the white of the calcium carbonate from which the shells are made, but some birds passerines, produce colored eggs. The pigment biliverdin and its zinc chelate give a green or blue ground color, protoporphyrin produces reds and browns as a ground color or as spotting. Non-passerines have white eggs, except in some ground-nesting groups such as the Charadriiformes and nightjars, where camouflage is necessary, some parasitic cuckoos which have to match the passerine host's egg. Most passerines, in contrast, lay colored eggs if there is no need of cryptic colors; however some have suggested that the protoporphyrin markings on passerine eggs act to reduce brittleness by acting as a solid state lubricant. If there is insufficient calcium available in the local soil, the egg shell may be thin in a circle around the broad end. Protoporphyrin speckling compensates for this, increases inversely to the amount of calcium in the soil. For the same reason eggs in a clutch are more spotted than early ones as the female's store of calcium is depleted.
The color of individual eggs is genetically influenced, appears to be inherited through the mother only, suggesting that the gene responsible for pigmentation is on the sex determining W chromosome. It used to be thought that color was applied to the shell before laying, but this research shows that coloration is an integral part of the development of the shell, with the same protein responsible for depositing calcium carbonate, or protoporphyrins when there is a lack of that mineral. In species such as the common guillemot, which nest in large groups, each female's eggs have different markings, making it easier for females to identify their own eggs on the crowded cliff ledges on which they breed. Bird eggshells are diverse. For example: cormorant eggs are rough and chalky tinamou eggs are shiny duck eggs are oily and waterproof cassowary eggs are pittedTiny pores in bird eggshells allow the embryo to breathe; the domestic
A crossed letter is a manuscript letter which contains two separate sets of writing, one written over the other at right-angles. This was done during the early days of the postal system in the 19th century to save on expensive postage charges, as well as to save paper; this technique is called cross-hatching or cross-writing. A cross letter is distinct from a palimpsest, as cross-hatched manuscripts were written this way at one sitting or for the same purpose, rather than being re-used later. Media related to Crossed letters at Wikimedia Commons
The symbol # is most known as the number sign, hash, or pound sign. The symbol has been used for a wide range of purposes, including the designation of an ordinal number and as a ligatured abbreviation for pounds avoirdupois. Since 2007, widespread usage of the symbol to introduce metadata tags on social media platforms has led to such tags being known as "hashtags" and from that, the symbol itself is sometimes incorrectly called a "hashtag"; the symbol is defined in ASCII as U +0023 # NUMBER SIGN and & num. It is graphically similar to several other symbols, including the sharp from musical notation and the equal-and-parallel symbol from mathematics, but is distinguished by its combination of level horizontal strokes and right-tilting vertical strokes, it is believed that the symbol traces its origins to the symbol ℔, an abbreviation of the Roman term libra pondo, which translates as "pound weight". This abbreviation was printed with a dedicated ligature type, with a horizontal line across, so that the lowercase letter "l" would not be mistaken for the numeral "1".
The symbol was reduced for clarity as an overlay of two horizontal strokes "=" across two slash-like strokes "//". Examples of it being used to indicate pounds exist at least as far back as 1850; the symbol is described as the "number" character in an 1853 treatise on bookkeeping. And its double meaning is described in a bookkeeping text from 1880; the instruction manual of the Blickensderfer model 5 typewriter appears to refer to the symbol as the "number mark". Some early-20th-century U. S. sources refer to it as the "number sign", although this could refer to the numero sign. A 1917 manual distinguishes between two uses of the sign: "number"; the use of the phrase "pound sign" to refer to this symbol is found from 1932 in U. S. usage. Before this time, still outside the United States, the term "pound sign" was used to refer to the pound currency symbol or the pound weight symbol. An alternative theory is that the name "pound sign" arose from the fact that character encodings used the same code for both the number sign and the British pound sign "£".
Claims have included ISO 646-GB as well as the Baudot code in the late 19th century. The apparent use of the sign to mean pounds weight in 1850 appears to rule out both of these code sets as the origin, although that same reference admits that the earliest reference in print was a decade after Baudot code."Hash sign" is found in South African writings from the late 1960s, from other non-North-American sources in the 1970s. The symbol appears to be used in handwritten material, while in the printing business, the numero symbol and barred-lb are used for "number" and "pounds" respectively. For mechanical devices, it appeared on the keyboard of the Remington Standard typewriter, but was not used on the keyboards used for typesetting, it appeared in many of the early teleprinter codes and from there was copied to ASCII which made it available on computers and thus caused many more uses to be found for the character. The symbol was introduced on the bottom right button of touch-tone keypads in 1968, but that button was not extensively used until the advent of large scale voicemail in the early 1980s.
Mainstream use in the United States is as follows: when it prefixes a number, it is read as "number", as in "a #2 pencil". The one exception is with the # key on a phone, always referred to as the "pound key" or "pound", thus instructions to dial an extension such as #77 are always read as "pound seven seven". When the symbol follows a number, the symbol indicates weight in pounds; this traditional usage still finds handwritten use, may be seen on some signs in markets and groceries. It is commonly known as the "pound sign". In Canada the symbol is called both the "number sign" and the "pound sign"; the American company Avaya has an option in their programming to denote Canadian English, which in turn instructs the system to say "number sign" to callers instead of "pound sign". In the United Kingdom and Ireland, it is called a hash, it is not used as weight or currency. It is not called the "pound sign"; the use of "#" as an abbreviation for "number" may be understood in Britain and Ireland, where there has been business or educational contact with American usage, but use in print is rare and British typewriters had "£" in place of the American "#".
Where Americans might write "Symphony #5", the British and Irish are more to write "Symphony No. 5", or use the numero sign—"Symphony № 5". To add to the confusion between "£" and "#", in BS 4730, 0x23 represents "£", whereas in ASCII, it represents "#", thus it was common for the same character code to display "#" on US equipment and "£" on British equipment; the symbol has many other names in English: Comment sign Taken from its use in many shell scripts and some programming languages to start comments. Hash, or hash mark Hashtag The word "hashtag" is used when reading social media messages aloud, indicating the start of a hashtag. For instance the text "#foo" is read out loud as "hashtag, foo" (as opposed to "h
Contrast is the difference in luminance or colour that makes an object distinguishable. In visual perception of the real world, contrast is determined by the difference in the color and brightness of the object and other objects within the same field of view; the human visual system is more sensitive to contrast than absolute luminance. The maximum contrast of an image is dynamic range. According to Campbell and Robson, the human contrast sensitivity function shows a typical band-pass filter shape peaking at around 4 cycles per degree with sensitivity dropping off either side of the peak; this finding has led many to claim that the human visual system is most sensitive in detecting contrast differences occurring at 4 cycles per degree. However, the claim of frequency sensitivity is problematic given, for example, that changes of distance don't seem to affect the relevant perceptual patterns (as noted, for example, in the figure caption to Solomon and Pelli While the latter authors are referring to letters, they make no objective distinction between these and other shapes.
The relative insensitivity of contrast effects to distance may be observed by casual inspection of a paradigmantic sweep grating, as may be observed here The high-frequency cut-off represents the optical limitations of the visual system's ability to resolve detail and is about 60 cycles per degree. The high-frequency cut-off is related to the packing density of the retinal photoreceptor cells: a finer matrix can resolve finer gratings; the low frequency drop-off is due to lateral inhibition within the retinal ganglion cells. A typical retinal ganglion cell presents a centre region with either excitation or inhibition and a surround region with the opposite sign. By using coarse gratings, the bright bands fall on the inhibitory as well as the excitatory region of the ganglion cell resulting in lateral inhibition and account for the low-frequency drop-off of the human contrast sensitivity function. One experimental phenomenon is the inhibition of blue in the periphery if blue light is displayed against white, leading to a yellow surrounding.
The yellow is derived from the inhibition of blue on the surroundings by the center. Since white minus blue is red and green, this mixes to become yellow. For example, in the case of graphical computer displays, contrast depends on the properties of the picture source or file and the properties of the computer display, including its variable settings. For some screens the angle between the screen surface and the observer's line of sight is important. There are many possible definitions of contrast; some include color. Travnikova laments, "Such a multiplicity of notions of contrast is inconvenient, it complicates the solution of many applied problems and makes it difficult to compare the results published by different authors."Various definitions of contrast are used in different situations. Here, luminance contrast is used as an example, but the formulas can be applied to other physical quantities. In many cases, the definitions of contrast represent a ratio of the type Luminance difference Average luminance.
The rationale behind this is that a small difference is negligible if the average luminance is high, while the same small difference matters if the average luminance is low. Below, some common definitions are given. Weber contrast is defined as I − I b I b, with I and I b representing the luminance of the features and the background, respectively; the measure is referred to as Weber fraction, since it is the term, constant in Weber's Law. Weber contrast is used in cases where small features are present on a large uniform background, i.e. where the average luminance is equal to the background luminance. Michelson contrast is used for patterns where both bright and dark features are equivalent and take up similar fractions of the area; the Michelson contrast is defined as I m a x − I m i n I m a x + I m i n, with I m a x and I m i n representing the highest and lowest luminance. The denominator represents twice the average of minimum luminances; this form of contrast is an effective way to quantify contrast for periodic functions f and is known as the modulation mf of a periodic signal f.
Modulation quantifies the relative amount by which the amplitude /2 of f stands out from the average