Chalk
Chalk is a soft, porous, sedimentary carbonate rock, a form of limestone composed of the mineral calcite. Calcite is an ionic salt called calcium carbonate or CaCO3, it forms under reasonably deep marine conditions from the gradual accumulation of minute calcite shells shed from micro-organisms called coccolithophores. Flint is common as bands parallel to the bedding or as nodules embedded in chalk, it is derived from sponge spicules or other siliceous organisms as water is expelled upwards during compaction. Flint is deposited around larger fossils such as Echinoidea which may be silicified. Chalk as seen in Cretaceous deposits of Western Europe is unusual among sedimentary limestones in the thickness of the beds. Most cliffs of chalk have few obvious bedding planes unlike most thick sequences of limestone such as the Carboniferous Limestone or the Jurassic oolitic limestones; this indicates stable conditions over tens of millions of years. Chalk has greater resistance to weathering and slumping than the clays with which it is associated, thus forming tall, steep cliffs where chalk ridges meet the sea.
Chalk hills, known as chalk downland form where bands of chalk reach the surface at an angle, so forming a scarp slope. Because chalk is well jointed it can hold a large volume of ground water, providing a natural reservoir that releases water through dry seasons. Chalk is mined from chalk deposits both above underground. Chalk mining boomed during the Industrial Revolution, due to the need for chalk products such as quicklime and bricks; some abandoned chalk mines remain tourist destinations due to their massive expanse and natural beauty. The Chalk Group is a European stratigraphic unit, it forms the famous White Cliffs of Dover in Kent, England, as well as their counterparts of the Cap Blanc Nez on the other side of the Dover Strait. The Champagne region of France is underlain by chalk deposits, which contain artificial caves used for wine storage; some of the highest chalk cliffs in the world occur at Jasmund National Park in Germany and at Møns Klint in Denmark – both once formed a single island.
Ninety million years ago what is now the chalk downland of Northern Europe was ooze accumulating at the bottom of a great sea. Chalk was one of the earliest rocks made up of microscopic particles to be studied under the microscope, when it was found to be composed entirely of coccoliths, their shells were made of calcite extracted from the rich seawater. As they died, a substantial layer built up over millions of years and, through the weight of overlying sediments became consolidated into rock. Earth movements related to the formation of the Alps raised these former sea-floor deposits above sea level; the chemical composition of chalk is calcium carbonate, with minor amounts of clay. It is formed in the sea by sub-microscopic plankton, which fall to the sea floor and are consolidated and compressed during diagenesis into chalk rock. Most people first encounter the word "chalk" in school where it refers to blackboard chalk, made of mineral chalk, since it crumbles and leaves particles that stick loosely to rough surfaces, allowing it to make writing that can be erased.
Blackboard chalk manufacture now may use mineral chalk, other mineral sources of calcium carbonate, or the mineral gypsum. While gypsum-based blackboard chalk is the lowest cost to produce, thus used in the developing world, calcium-based chalk can be made where the crumbling particles are larger and thus produce less dust, is marketed as "dustless chalk". Colored chalks, pastel chalks, sidewalk chalk, used to draw on sidewalks and driveways, are made of gypsum. Chalk is a source of quicklime by thermal decomposition, or slaked lime following quenching of quicklime with water. In southeast England, deneholes are a notable example of ancient chalk pits; such bell pits may mark the sites of ancient flint mines, where the prime object was to remove flint nodules for stone tool manufacture. The surface remains at Cissbury are one such example, but the most famous is the extensive complex at Grimes Graves in Norfolk. Woodworking joints may be fitted by chalking one of the mating surfaces. A trial fit will leave a chalk mark on the high spots of the corresponding surface.
Chalk transferring to cover the complete surface indicates a good fit. Builder's putty mainly contains chalk as a filler in linseed oil. Chalk may be used for its properties as a base. In agriculture, chalk is used for raising pH in soils with high acidity; the most common forms are CaCO3 and CaO. Small doses of chalk can be used as an antacid. Additionally, the small particles of chalk make it a substance ideal for polishing. For example, toothpaste contains small amounts of chalk, which serves as a mild abrasive. Polishing chalk is chalk prepared with a controlled grain size, for fine polishing of metals. Chalk can be used as fingerprint powder. Several traditional uses of chalk have been replaced by other substances, although the word "chalk" is still applied to the usual replacements. Tailor's chalk is traditionally a hard chalk used to make temporary markings on cloth by tailors, it is now made of talc. Chalk was traditionally used in recreation. In field sports, such as tennis played on grass, powdered chalk was used to mark the boundary lines of the playing field or court.
If a ball hits the line, a cloud of chalk or p
Sizing
Sizing or size is any one of numerous substances, applied to, or incorporated into, other materials—especially papers and textiles—to act as a protective filler or glaze. Sizing is used in papermaking and textile manufacturing to change the absorption and wear characteristics of those materials. Sizing is used for oil-based surface preparation for gilding, it is used by artists to prepare paper and textile surfaces for some art techniques. Sizing is used during paper manufacture to reduce the paper's tendency when dry to absorb liquid, with the goal of allowing inks and paints to remain on the surface of the paper and to dry there, rather than be absorbed into the paper; this provides a more consistent and precise printing and writing surface. This is achieved by curbing the paper fibers' tendency to absorb liquids by capillary action. In addition, sizing affects abrasiveness, finish, printability and surface bond strength and decreases surface porosity and fuzzing. There are three categories of papers with respect to sizing: unsized, weak sized, strong sized.
Waterleaf includes absorbent papers for blotting. Slack sized paper is somewhat absorbent and includes newsprint, while hard sized papers have the highest water resistance, such as coated fine papers and liquid packaging board. There are two types of sizing: internal sizing, sometimes called engine sizing, surface sizing. Internal sizing is applied to all papers and to all those that are machine made, while surface sizing is added for the highest grade bond and writing papers. Surface sizing solutions consist of modified starches and sometimes other hydrocolloids, such as gelatine, or surface sizing agents such as acrylic co-polymers. Surface sizing agents are amphiphilic molecules, having both hydrophobic ends; the sizing agent adheres to substrate fibers and forms a film, with the hydrophilic tail facing the fiber and the hydrophobic tail facing outwards, resulting in a smooth finish that tends to be water-repellent. Sizing improves the surface strength and water resistance of the paper or material to which it is applied.
In the sizing solution, optical brightening agents may be added to improve the opacity and whiteness of the paper or material surface. Internal sizing chemicals used in papermaking at the wet end are alkyl succinic anhydride, alkyl ketene dimer and rosin. By making the paper web more hydrophobic, the sizing agents influence dewatering and retention of fillers and fibers in the paper sheet. Next to paper quality, internal sizing agents' main effect is on runability of the paper machine. While sizing is intended to make paper more suitable for printing, it makes printing paper less durable and poses a problem for preservation of printed documents. Sizing with starch was introduced quite early in the history of papermaking. Dard Hunter in Papermaking through Eighteen Centuries corroborates this by writing, "The Chinese used starch as a size for paper as early as A. D. 768 and its use continued until the fourteenth century when animal glue was substituted." In the early modern paper mills in Europe, which produced paper for printing and other uses, the sizing agent of choice was gelatin, as Susan Swartzburg writes in Preserving Library Materials': "Various substances have been used for sizing through the ages, from gypsum to animal gelatin."
Hunter describes the process of sizing in these paper mills in the following: The drying completed, the old papermakers dipped their paper into an animal size, made from the parings of hides, which they procured from the parchment-makers. It was necessary to size that paper so that it would be impervious to ink, but sizing was more needed in writing than in printing papers. Many books of the fifteenth century were printed upon paper that had not been sized, this extra treatment not being essential for a type impression; the sizing was accomplished by a worker holding a number of sheets by the aid of two wooden sticks, dipping the paper into the warm gelatinous liquid. The sheets were pressed to extract the superfluous gelatine; this crude method of sizing the paper was wasteful as many sheets were torn and bruised beyond use. The sizing room of the early paper mills, for this reason, known as the'slaughter-house'. With the advent of the mass production of paper, the type of size used for paper production changed.
As Swartzburg writes, "By 1850 rosin size had come into use. It produces a chemical action that hastens the decomposition of the finest papers." In the field of library preservation it is known "that acid hydrolysis of cellulose and related carbo-hydrates is one of the key factors responsible for the degradation of paper during ageing." Some professional work has focused on the specific processes involved in the degradation of rosin-sized paper, in addition to work on developing permanent paper and sizing agents that will not destroy the paper. An issue on the periphery to the preservation of paper and sizing, is washing, described by V. Daniels and J. Kosek as, "The removal of discolouration... in water is principally effected by the dissolution of water-soluble material. In such a process, surface level items applied to the paper, such as size in early paper making processes as seen above, have the possibility of being removed from the paper, which might have some item specific interest in a special collections library.
With processes in paper making being more akin to "engine sizing," as H
Tempera
Tempera known as egg tempera, is a permanent, fast-drying painting medium consisting of colored pigments mixed with a water-soluble binder medium glutinous material such as egg yolk. Tempera refers to the paintings done in this medium. Tempera paintings are long lasting, examples from the first century CE still exist. Egg tempera was a primary method of painting until after 1500 when it was superseded by the invention of oil painting. A paint consisting of pigment and binder used in the United States as poster paint is often referred to as "tempera paint," although the binders in this paint are different from traditional tempera paint. Tempera painting has been found on early Egyptian sarcophagi decorations. Many of the Fayum mummy portraits use tempera, sometimes in combination with encaustic. A related technique has been used in ancient and early medieval paintings found in several caves and rock-cut temples of India. High-quality art with the help of tempera was created in Bagh Caves between the late 4th and 10th centuries CE and in the 7th century CE in Ravan Chhaya rock shelter, Orissa.
The art technique was known from the classical world, where it appears to have taken over from encaustic painting and was the main medium used for panel painting and illuminated manuscripts in the Byzantine world and Medieval and Early renaissance Europe. Tempera painting was the primary panel painting medium for nearly every painter in the European Medieval and Early renaissance period up to 1500. For example, every surviving panel painting by Michelangelo is egg tempera. Oil paint, which may have originated in Afghanistan between the 5th and 9th centuries and migrated westward in the Middle Ages superseded tempera. Oil replaced tempera as the principal medium used for creating artwork during the 15th century in Early Netherlandish painting in northern Europe. Around 1500, oil paint replaced tempera in Italy. In the 19th and 20th centuries, there were intermittent revivals of tempera technique in Western art, among the Pre-Raphaelites, Social Realists, others. Tempera painting continues to be used in Greece and Russia where it is the traditional medium for Orthodox icons.
The term tempera is derived from the Late Latin distemperare. Tempera is traditionally created by hand-grinding dry powdered pigments into a binding agent or medium, such as egg yolk, milk and a variety of plant gums; the most common form of classical tempera painting is "egg tempera". For this form most only the contents of the egg yolk is used; the white of the egg and the membrane of the yolk are discarded. Egg yolk is used by itself with pigment; some agent is always added, in variable proportions. One recipe calls for vinegar, but only in small amounts. A few drops of vinegar will preserve the solution for a week. (1:3, 3 parts water, 1 part yolk. Some schools of egg tempera use various mixtures of egg water. Powdered pigment, or pigment, ground in distilled water, is placed onto a palette or bowl and mixed with a equal volume of the binder; some pigments require more binder, some require less. When used to paint icons on church walls, liquid myrrh is sometimes added to the mixture to give the paint a pleasing odor as worshipers may find the egg tempera somewhat pungent for quite some time after completion.
The paint mixture has to be adjusted to maintain a balance between a "greasy" and "watery" consistency by adjusting the amount of water and yolk. As tempera dries, the artist will add more water to preserve the consistency and to balance the thickening of the yolk on contact with air. Once prepared, the paint cannot be stored. Egg tempera is not waterproof. Different preparations use the egg white or the whole egg for a different effect. Other additives such as oil and wax emulsions can modify the medium. Egg tempera requires stiff boards. Adding oil in no more than a 1:1 ratio with the egg yolk by volume produces a water-soluble medium with many of the color effects of oil paint, although it cannot be painted thickly; some of the pigments used by medieval painters, such as cinnabar, orpiment, or lead white are toxic. Most artists today use modern synthetic pigments, which are less toxic but have similar color properties to the older pigments. So, many modern pigments are still dangerous unless certain precautions are taken.
Tempera paint dries rapidly. It is applied in thin, semi-opaque or transparent layers. Tempera painting allows for great precision when used with traditional techniques that require the application of numerous small brush strokes applied in a cross-hatching technique; when dry, it produces a smooth matte finish. Because it cannot be applied in thick layers as oil paints can, tempera paintings have the deep color saturation that oil paintings can achieve because it can hold less pigment. In this respect, the colors of an unvarnished tempera painting resemble a pastel, although the color deepens if a varnish is applied. On the other hand, tempera colors do not change over time, whereas oil paints darken and become transparent with age. Tempera adheres best to an absorbent ground that has a lower oil co
Walter Crane
Walter Crane was an English artist and book illustrator. He is considered to be the most influential, among the most prolific, children’s book creators of his generation and, along with Randolph Caldecott and Kate Greenaway, one of the strongest contributors to the child's nursery motif that the genre of English children's illustrated literature would exhibit in its developmental stages in the 19th century. Crane's work featured some of the more colourful and detailed beginnings of the child-in-the-garden motifs that would characterize many nursery rhymes and children's stories for decades to come, he was part of the Arts and Crafts movement and produced an array of paintings, children's books, ceramic tiles and other decorative arts. Crane is remembered for his creation of a number of iconic images associated with the international Socialist movement. Crane was the second son of Thomas Crane, a portrait painter and miniaturist, Marie Crane, the daughter of a prosperous malt-maker, his elder brother Thomas would go into illustration, sister Lucy was a noted writer.
He was a fluent follower of the newer art movements and he came to study and appreciate the detailed senses of the Pre-Raphaelite Brotherhood, was a diligent student of the renowned artist and critic John Ruskin. A set of coloured page designs to illustrate Tennyson's "Lady of Shalott" gained the approval of wood-engraver William James Linton to whom Walter Crane was apprenticed for three years in 1859–62; as a wood-engraver he had abundant opportunity for the minute study of the contemporary artists whose work passed through his hands, of Pre-Raphaelites Dante Gabriel Rossetti and John Everett Millais, as well as Alice in Wonderland illustrator Sir John Tenniel and Frederick Sandys. He was a student who admired the masters of the Italian Renaissance, however he was more influenced by the Elgin marbles in the British Museum. A further and important element in the development of his talent was the study of Japanese colour-prints, the methods of which he imitated in a series of toy books, which started a new fashion.
From the early 1880s under William Morris's influence, Crane was associated with the Socialist movement. He did as much as Morris. With this object in view he devoted much attention to designs for textiles and wallpapers, to house decoration. For a long time he provided the weekly cartoons for the Socialist organs Justice, The Commonweal and The Clarion. Many of these were collected as Cartoons for the Cause, he devoted much time and energy to the work of the Art Workers Guild, of which he was master in 1888 and 1889 and to the Arts and Crafts Exhibition Society, which he helped to found in 1888. He was a Vice President of the Healthy and Artistic Dress Union, a movement begun in 1890, whose aim was to promote the loose-fitting clothing, in opposition to "stiffness and weight", they produced numerous pamphlets setting out their cause, including one entitled "How to Dress Without a Corset" which Crane illustrated. Although not himself an anarchist, Crane contributed to several libertarian publishers, including Liberty Press and Freedom Press.
He is credited with the design and decoration of the front facade of "The Bomb Shop", Henderson's bookshop at 66 Charing Cross Road specialising in left-wing and radical literature. Crane was controversial in his support of the four Chicago anarchists executed in 1887 in connection with the Haymarket affair. Visiting the United States for the first time in connection with an exhibition of his work in 1891, Crane scandalized polite society by appearing at a Boston anarchist meeting and expressing the opinion that the Haymarket defendants had been put to death wrongfully. Returning to his hotel, Crane found a letter stating that he faced "hopeless ruin" among American patrons of the arts owing to his support of those who were considered to be terrorist conspirators in public opinion of the day. Financial support was withdrawn and planned dinners in Crane's honor were cancelled. In response to the controversy, Crane wrote a letter to the press explaining that he had not meant to cause insult and did not himself favor the use of explosives, but had been expressing his principled opinion that those convicted were innocent of the crime for which they were charged.
The incident was memorialized in the press as "probably the most dramatic episode" in the artist's career. Walter Crane died on 14 March 1915 in West Sussex, his body was cremated at the Golders Green Crematorium. He was survived by three children, Beatrice and Lancelot. In 1862 his picture The Lady of Shalott was exhibited at the Royal Academy, but the Academy refused his maturer work and after the opening of the Grosvenor Gallery in 1877, he ceased to send pictures to Burlington House. In 1863 the printer Edmund Evans employed Crane to illustrate yellowbacks, in 1865 they began to collaborate on toy books of nursery rhymes and fairy tales. From 1865 to 1876 Crane and Evans produced two to three toy books each year; these are a few of his illustration suites: In 1864 he began to illustrate a series of sixpenny toy books of nursery rhymes in three colours for Edmund Evans. He was allowed more freedom in a series beginning with The Frog Prince which showed markedly the influence of Japanese art, of a long visit to Italy following on his marriage in 1871.
His work was characterized by sharp flat tints. The Baby's Opera was a book of English nursery songs available in 1877 with Evans, a third series of children's books with the collective title Romance of
Work of art
A work of art, art piece, piece of art or art object is an aesthetic physical item or artistic creation. Apart from "work of art", which may be used of any work regarded as art in its widest sense, including works from literature and music, these terms apply principally to tangible, portable forms of visual art: An example of fine art, such as a painting or sculpture An object, designed for its aesthetic appeal, such as a piece of jewellery An object, designed for aesthetic appeal as well as functional purpose, as in interior design and much folk art An object created for principally or functional, religious or other non-aesthetic reasons which has come to be appreciated as art A non-ephemeral photograph, film or visual computer program, such as a video game or computer animation A work of installation art or conceptual art. Used more broadly, the term is less applied to: A fine work of architecture or landscape design A production of live performance, such as theater, opera, performance art, musical concert and other performing arts, other ephemeral, non-tangible creations.
This article is concerned with the terms and concept as used in and applied to the visual arts, although other fields such as aural-music and written word-literature have similar issues and philosophies. The term objet d'art is reserved to describe works of art that are not paintings, drawings or large or medium-sized sculptures, or architecture; the term oeuvre is used to describe the complete body of work completed by an artist throughout a career. A work of art in the visual arts is a physical two- or three- dimensional object, professionally determined or otherwise considered to fulfill a independent aesthetic function. A singular art object is seen in the context of a larger art movement or artistic era, such as: a genre, aesthetic convention, culture, or regional-national distinction, it can be seen as an item within an artist's "body of work" or oeuvre. The term is used by: museum and cultural heritage curators, the interested public, the art patron-private art collector community, art galleries.
Physical objects that document immaterial or conceptual art works, but do not conform to artistic conventions can be redefined and reclassified as art objects. Some Dada and Neo-Dada conceptual and readymade works have received inclusion; some architectural renderings and models of unbuilt projects, such as by Vitruvius, Leonardo da Vinci, Frank Lloyd Wright, Frank Gehry, are other examples. The products of environmental design, depending on intention and execution, can be "works of art" and include: land art, site-specific art, gardens, landscape architecture, installation art, rock art, megalithic monuments. Legal definitions of "work of art" are used in copyright law. Marcel Duchamp critiqued the idea that the work of art should be a unique product of an artist's labour, representational of their technical skill or artistic caprice. Theorists have argued that objects and people do not have a constant meaning, but their meanings are fashioned by humans in the context of their culture, as they have the ability to make things mean or signify something.
Artist Michael Craig-Martin, creator of An Oak Tree, said of his work – "It's not a symbol. I have changed the physical substance of the glass of water into that of an oak tree. I didn't change its appearance; the actual oak tree is physically present, but in the form of a glass of water." Some art theorists and writers have long made a distinction between the physical qualities of an art object and its identity-status as an artwork. For example, a painting by Rembrandt has a physical existence as an "oil painting on canvas", separate from its identity as a masterpiece "work of art" or the artist's magnum opus. Many works of art are denied "museum quality" or artistic merit, become accepted and valued in museum and private collections. Works by the Impressionists and non-representational abstract artists are examples. Some, such as the "Readymades" of Marcel Duchamp including his infamous urinal Fountain, are reproduced as museum quality replicas. There is an indefinite distinction, for current or historical aesthetic items: between "fine art" objects made by "artists".
Contemporary and archeological indigenous art, industrial design items in limited or mass production, places created by environmental designers and cultural landscapes, are some examples. The term has been available for debate and redefinition. Anti-art Artistic media Cultural artifact Opus number Outline of aesthetics The Work of Art in the Age of Mechanical Reproduction Western canon Richard Wollheim and Its Objects, 2nd ed. 1980, Cambridge University Press, ISBN 0-521-29706-0. The classic philosophical enquiry into what a work of art is. Media related to Art at Wikimedia Commons
Paint
Paint is any pigmented liquid, liquefiable, or mastic composition that, after application to a substrate in a thin layer, converts to a solid film. It is most used to protect, color, or provide texture to objects. Paint can be made or purchased in many colors—and in many different types, such as watercolor, etc. Paint is stored and applied as a liquid, but most types dry into a solid. In 2003 and 2004, South African archeologists reported finds in Blombos Cave of a 100,000-year-old human-made ochre-based mixture that could have been used like paint. Further excavation in the same cave resulted in the 2011 report of a complete toolkit for grinding pigments and making a primitive paint-like substance. Cave paintings drawn with red or yellow ochre, manganese oxide, charcoal may have been made by early Homo sapiens as long as 40,000 years ago. Ancient colored walls at Dendera, which were exposed for years to the elements, still possess their brilliant color, as vivid as when they were painted about 2,000 years ago.
The Egyptians mixed their colors with a gummy substance, applied them separately from each other without any blending or mixture. They appear to have used six colors: white, blue, red and green, they first covered the area with white traced the design in black, leaving out the lights of the ground color. They used minium for red, of a dark tinge. Pliny mentions some painted ceilings in his day in the town of Ardea, done prior to the foundation of Rome, he expresses great surprise and admiration after the lapse of so many centuries. Paint was made with the yolk of eggs and therefore, the substance would harden and adhere to the surface it was applied to. Pigment was made from plants and different soils. Most paints used either water as a base. A still extant example of 17th-century house oil painting is Ham House in Surrey, where a primer was used along with several undercoats and an elaborate decorative overcoat; the process was done by hand by the painters and exposed them to lead poisoning due to the white-lead powder.
In 1718, Marshall Smith invented Engine for the Grinding of Colours" in England. It is not known how it operated, but it was a device that increased the efficiency of pigment grinding dramatically. Soon, a company called Emerton and Manby was advertising exceptionally low-priced paints, ground with labour-saving technology: One Pound of Colour ground in a Horse-Mill will paint twelve Yards of Work, whereas Colour ground any other Way, will not do half that Quantity. By the proper onset of the Industrial Revolution, paint was being ground in steam-powered mills and an alternative to lead-based pigments was found in a white derivative of zinc oxide. Interior house painting became the norm as the 19th century progressed, both for decorative reasons and because the paint was effective in preventing the walls rotting from damp. Linseed oil was increasingly used as an inexpensive binder. In 1866, Sherwin-Williams in the United States opened as a large paint-maker and invented a paint that could be used from the tin without preparation.
It was not until the stimulus of World War II created a shortage of linseed oil in the supply market that artificial resins, or alkyds, were invented. Cheap and easy to make, they held the color well and lasted for a long time; the vehicle is composed of the binder. In this case, once the paint has dried or cured nearly all of the diluent has evaporated and only the binder is left on the coated surface. Thus, an important quantity in coatings formulation is the "vehicle solids", sometimes called the "resin solids" of the formula; this is the proportion of the wet coating weight, binder, i.e. the polymer backbone of the film that will remain after drying or curing is complete. The binder is the film-forming component of paint, it is the only component, always present among all the various types of formulations. Many binders must be thinned; the type of thinner, if present, varies with the binder. The binder imparts properties such as gloss, durability and toughness. Binders include synthetic or natural resins such as alkyds, vinyl-acrylics, vinyl acetate/ethylene, polyesters, melamine resins, silanes or siloxanes or oils.
Binders can be categorized according to the mechanisms for film formation. Thermoplastic mechanisms include coalescence. Drying refers to simple evaporation of the thinner to leave a coherent film behind. Coalescence refers to a mechanism that involves drying followed by actual interpenetration and fusion of discrete particles. Thermoplastic film-forming mechanisms are sometimes described as "thermoplastic cure" but, a misnomer because no chemical curing reactions are required to knit the film. Thermosetting mechanisms, on the other hand, are true curing mechanism that involve chemical reaction among the polymers that make up the binder. Thermoplastic mechanisms: Some films are formed by simple cooling of the binder. For example, encaustic or wax paints are liquid when warm, harden upon cooling. In many cases, they liquify if reheated. Paints that dry by solvent evaporation and contain the solid binder dissolved in a solvent are known as lacquers. A solid film forms; because no chemical crosslinking is involved, the film can re-dissolve in solvent.
Oil paint
Oil paint is a type of slow-drying paint that consists of particles of pigment suspended in a drying oil linseed oil. The viscosity of the paint may be modified by the addition of a solvent such as turpentine or white spirit, varnish may be added to increase the glossiness of the dried oil paint film. Oil paints have been used in Europe since the 12th century for simple decoration, but were not adopted as an artistic medium until the early 15th century. Common modern applications of oil paint are in finishing and protection of wood in buildings and exposed metal structures such as ships and bridges, its hard-wearing properties and luminous colors make it desirable for both interior and exterior use on wood and metal. Due to its slow-drying properties, it has been used in paint-on-glass animation. Thickness of coat has considerable bearing on time required for drying: thin coats of oil paint dry quickly; the technical history of the introduction and development of oil paint, the date of introduction of various additives is still—despite intense research since the mid 19th century—not well understood.
The literature abounds with incorrect theories and information: in general, anything published before 1952 is suspect. Until 1991 nothing was known about the organic aspect of cave paintings from the Paleolithic era. Many assumptions were made about the chemistry of the binders; the oldest known oil paintings date from 650 AD, found in 2008 in caves in Afghanistan's Bamiyan Valley, "using walnut and poppy seed oils." Though the ancient Mediterranean civilizations of Greece and Egypt used vegetable oils, there is little evidence to indicate their use as media in painting. Indeed, linseed oil was not used as a medium because of its tendency to dry slowly and crack, unlike mastic and wax. Greek writers such as Aetius Amidenus recorded recipes involving the use of oils for drying, such as walnut, hempseed, pine nut and linseed; when thickened, the oils became resinous and could be used as varnish to seal and protect paintings from water. Additionally, when yellow pigment was added to oil, it could be spread over tin foil as a less expensive alternative to gold leaf.
Early Christian monks used the techniques in their own artworks. Theophilus Presbyter, a 12th-century German monk, recommended linseed oil but advocated against the use of olive oil due to its long drying time. Oil paint was used as it is today in house decoration, as a tough waterproof cover for exposed woodwork outdoors. In the 13th century, oil was used to detail tempera paintings. In the 14th century, Cennino Cennini described a painting technique utilizing tempera painting covered by light layers of oil; the slow-drying properties of organic oils were known to early painters. However, the difficulty in acquiring and working the materials meant that they were used; as public preference for naturalism increased, the quick-drying tempera paints became insufficient to achieve the detailed and precise effects that oil could achieve. The Early Netherlandish painting of the 15th century saw the rise of the panel painting purely in oils, or oil painting, or works combining tempera and oil painting, by the 16th century easel painting in pure oils had become the norm, using much the same techniques and materials found today.
The claim by Vasari that Jan van Eyck "invented" oil painting, while it has cast a long shadow, is not correct, but van Eyck's use of oil paint achieved novel results in terms of precise detail and mixing colours wet-on-wet with a skill hardly equalled since. Van Eyck’s mixture may have consisted of piled glass, calcined bones, mineral pigments boiled in linseed oil until they reached a viscous state—or he may have used sun-thickened oils, he left no written documentation. The Flemish-trained or influenced Antonello da Messina, who Vasari wrongly credited with the introduction of oil paint to Italy, does seem to have improved the formula by adding litharge, or lead oxide; the new mixture had better drying properties. This mixture was known as oglio cotto—"cooked oil." Leonardo da Vinci improved these techniques by cooking the mixture at a low temperature and adding 5 to 10% beeswax, which prevented darkening of the paint. Giorgione and Tintoretto each may have altered this recipe for their own purposes.
The paint tube was invented in 1841 by portrait painter John Goffe Rand, superseding pig bladders and glass syringes as the primary tool of paint transport. Artists, or their assistants ground each pigment by hand mixing the binding oil in the proper proportions. Paints could now be sold in tin tubes with a cap; the cap could be screwed back on and the paints preserved for future use, providing flexibility and efficiency to painting outdoors. The manufactured paints had a balanced consistency that the artist could thin with oil, turpentine, or other mediums. Paint in tubes changed the way some artists approached painting; the artist Pierre-Auguste Renoir said, “Without tubes of paint, there would have been no Impressionism.” For the impressionists, tubed paints offered an accessible variety of colors for their plein air palettes, motivating them to make spontaneous color choices. With greater quantities of preserved paint, they were able to apply paint more thickly. Traditional oil paints require an oil that always hardens, forming a impermeable film.
Such oils are called siccative, or drying and are characterized by high levels of po
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