WhatsApp usOur definitive glossary of art materials brings together an extensive range of traditional and contemporary techniques used across the visual arts. Designed as both a practical reference for conservators, artists, collectors and an educational resource for those interested in material history, this glossary traces how creative media have evolved, from natural pigments to synthetic polymers. This series also covers:
Join our team of experts as they explain the composition and use of each material or process, with attention to the qualities that influence an artwork’s appearance. By understanding the physical nature of art, we gain deeper insight into the artist’s methods, the ageing process of objects and the delicate balance between preservation and presentation that defines art conservation today.
Painting Materials & Techniques
Acrylic
Paint made with a pigment mixed in a plastic-based emulsion. Developed commercially in the mid 20th century, acrylics dry quickly, are water-soluble when wet and form a flexible, durable surface when dry. The medium adapts to a wide range of techniques from thin washes to thick impasto. The invention of acrylic paint followed advances in polymer chemistry during the early 1900s. The first art grade acrylics appeared in the 1940s, followed by water-based emulsions in the late 1950s. Their ease of use and compatibility with other media aligned perfectly with the experimental art of post-war modernism and the pop art movement. Notable artists who use acrylic include Andy Warhol, Bridget Riley, Mark Rothko, David Hockney, Helen Frankenthaler and Roy Lichtenstein.
Alla Prima
Direct painting technique in which the artwork is completed in a single session, applied wet-into-wet without an underpainting or successive layers. The term comes from the Italian meaning “at first attempt” arequires confidence and allows for spontaneous blending and visible brushwork. The technique gained prominence in the 19th century with the rise of plein-air and impressionist paintings. The alla prima approach symbolised a shift from the methodical, layered traditions of academic painting to a more direct and modern expression.
Cadmium
Vivid pigments of yellows, oranges and reds derived from cadmium sulfide and cadmium selenide compounds. Introduced in the mid 19th century, cadmium pigments offered artists durable, brilliant alternatives to less stable chrome and vermilion pigments. Their toxicity limited industrial use, but they remained popular in fine art for their intensity and permanence. Monet and Matisse used cadmium pigments in their impressionist works. Georgia O’Keeffe applied cadmium reds and oranges in her floral pieces and Mark Rothko used them for the saturated fields in his abstract compositions.
Above: painting detail showing the use of cadium in a portrait of Madame Joseph-Michel Ginoux by Vincent van Gogh, 1888-89
Casein
Paint made from milk protein mixed with pigment, producing a matte, opaque surface. It dries quickly to a hard, water-resistant film and was historically favoured for its smooth finish and subtle luminosity. Casein can be used as an independent medium or as an underpainting layer for oils. It has a velvety, chalk-like texture. Casein painting dates back to ancient Egypt, where milk-based binders were used on tomb decorations and wooden panels. In the early 20th century, casein became a popular choice for illustrators, muralists and designers before the advent of acrylics, as it combined the permanence of tempera with the handling qualities of watercolour.
Cobalt
Bright blue pigment made from cobalt aluminate. It is valued for its clarity and opacity, offering a cooler tone than ultramarine. Developed in 1802 by Louis Jacques Thénard, cobalt blue quickly became a favourite among 19th century artists, replacing costly natural blues. Turner, Monet and Renoir used cobalt blue extensively. Vincent van Gogh relied on it for his masterpiece Starry Night.
Tempera
Traditional painting medium made by mixing finely ground pigment with an egg yolk binder. Tempera paint dries quickly to a smooth, matte surface and allows for precise brushwork. Painting with tempera dates back to antiquity, it was used in Egyptian panels and early Christian icons. It became the dominant medium of the Middle Ages and early Renaissance, particularly for panel paintings and altarpieces before the development of oil paint. Though gradually replaced by oil paint in the 15th century, tempera remained prized for its purity of colour and fine detail. Tempera was used by artists such as Sandro Botticelli, Giotto di Bondone and Duccio di Buoninsegna. In the 20th century, Andrew Wyeth and George Tooker revived the medium.
Above: an example of tempera used to compose The Three Miracles of Saint Zenobius by Botticelli, 16th century
Encaustic
Technique using heated beeswax mixed with coloured pigments, applied to a rigid surface such as wood or canvas. The wax medium produces a lustrous, durable finish that allows for rich texture, translucent layering and a unique depth of colour. Once cooled, the surface can be polished or reworked by reheating. Encaustic painting originated in ancient Greece and Rome, where it was used for the decoration of interiors, ships and sculpture. The technique is most famously seen in the Fayum mummy portraits. After declining in use during the Middle Ages due to its technical demands, encaustic was rediscovered in the 18th and 19th centuries. It gained renewed attention in the 20th century thanks to modernist experimentation.
Fresco
Painting on freshly laid (wet) lime plaster, where pigments are applied in water and bond chemically with the surface as it dries. This technique, known as buon fresco, creates a permanent, durable image that becomes part of the wall itself. Artists often worked in sections called giornate, completing each area before the plaster set. A related process, fresco secco, involves painting on dry plaster with added binders. Notable fresco artists include Giotto di Bondone in Padua’s Scrovegni Chapel and Michelangelo in the Sistine Chapel as well as examples by Raphael, Piero della Francesca and Masaccio. Diego Rivera revived fresco works in the 20th century muralism movement.
Sizing
Preparatory substance on canvas or other supports to control absorbency and strengthen the surface before paint is applied. Sizing prevents paint from soaking too deeply into the fibres, allowing colours to sit on the surface with greater brilliance and stability (see notes on ground layer).
Gouache
Opaque watercolour made by adding chalk or white pigment to traditional watercolour, producing a dense, matte finish with strong colour coverage. Gouache dries quickly and can be reactivated with water, making it a favourite for illustration, design and fine art where precision and flat colour are required. The medium has ancient origins, it can be found in Persian and Mughal miniatures and European medieval manuscripts such as Books of Hours. Gouache was used in topographical painting and botanical studies, you can also find it in the illustrations of Beatrix Potter. Notable modern artists who used gouache include Henri Matisse, Paul Klee and Marc Chagall.
Above: detail with an example of gouache and watercolour in The Lake of Zug by JMW Turner, 1843
Gesso
White preparatory coating made from chalk or gypsum mixed with animal glue, applied to canvas, panel or plaster to create a smooth, absorbent surface for painting. Traditional gesso, known as gesso sottile, was used in tempera and early oil painting, while modern acrylic gesso substitutes synthetic polymers for greater flexibility. It serves as both a ground and a barrier, preventing paint from soaking into the support.
Grattage
Painting technique in which layers of wet or semi-dry paint are scraped or scratched away to reveal colours or textures beneath. Derived from the French word gratter “to scrape” artists often apply grattage with blades. Grattage became a recognised modernist process in the early 20th century, particularly associated with the Surrealist movement. It developed in parallel with frottage (rubbing) as part of an effort to allow accidental textures to emerge. Max Ernst, Jean Dubuffet and Gerhard Richter employed scraping as an expressive technique.
Prussian Blue
One of the first modern synthetic pigments, composed of ferric ferrocyanide. It produces a deep, cool blue with a slight greenish tint. Accidentally discovered in Berlin around 1704, Prussian blue quickly became a revolutionary colour in European art, replacing expensive natural blues like ultramarine. It was widely used in oil, watercolour and printmaking and even as a dye for textiles and blueprints (cyanotypes). Canaletto and Jean-Baptiste-Siméon Chardin adopted it early in the 18th century. Pablo Picasso used it extensively during his Blue Period.
Impasto
Artistic technique involving the thick, textured application of paint that creates raised surfaces on the canvas. Often applied with a palette knife or heavily loaded brush, impasto allows visible brushstrokes and plays dramatically with light and shadow, enhancing depth. It is most commonly associated with oil painting, though it is also used in acrylics. Rembrandt, Titian and Velázquez pioneered early uses of impasto. Later, it is found in the work of Van Gogh, Claude Monet and the impressionists, who employed it to capture the vibrancy of light. In modern art, impasto was used by Frank Auerbach, Leon Kossoff and Anselm Kiefer.
Above: a detail of impasto roses in a 1890 work by Vincent van Gogh
Oil Paint
Paint made by mixing finely ground pigments with drying oils such as linseed, walnut or poppyseed. Oil paint was developed in Northern Europe during the 15th century. Jan van Eyck is often credited with perfecting early oil techniques. The medium spread quickly through the Italian Renaissance and became the standard for easel painting across Europe. Most of the worlds masterpieces were completed in oil paint, as it was used by a vast number of artists from Leonardo da Vinci to Pablo Picasso.
Mahlstick
Long, slender stick with a padded or soft leather head at one end, used by painters to steady the hand while working on fine details or delicate areas of a painting. The mahlstick is typically rested against the edge of the canvas or easel, allowing the artist’s hand to hover just above the surface without smudging wet paint.
Varnish
A transparent protective coating applied to finished paintings to enrich colour depth, unify surface sheen and shield the paint layer from dust, moisture and abrasion. Traditionally, oil painting varnish was made from natural resins such as dammar, mastic or copal dissolved in turpentine, varnishes form a reversible layer that can be removed or replaced during conservation. Modern synthetic varnishes, like acrylic or ketone resins, offer greater stability and resistance to yellowing. The practice of varnishing dates back to the Renaissance, when artists sought to imitate the glowing luminosity of freshly painted oil surfaces.
Verdigris
Green pigment or patina that forms naturally on copper, bronze and brass as the metal oxidises. It can be artificially produced using vinegar vapours. Chemically composed of basic copper acetates or carbonates, verdigris has been prized since antiquity for its vivid turquoise-green hue, though it is known to be chemically unstable and can darken or corrode adjacent pigments over time. Verdigris was often applied in glazes to create luminous green tones in foliage and drapery. However, its tendency to darken and react with binding media make it a conservation challenge.
Above: detail from a watercolour painting of Bamborough Castle Northumberland by John Varley, 1827
Watercolour
Paint made from pigments suspended in a water soluble binder such as gum arabic. Watercolour paint cannot easily be corrected, so the application demands precision and confidence. Used since ancient Egypt and refined during the Renaissance for drawings and manuscript illumination, watercolour became a major independent medium in the 18th and 19th centuries, especially in Britain for landscape painting and botanical illustration. The invention of portable paint made it popular with travellers and plein air artists. Notable artists that worked with watercolour include J.M.W. Turner, Winslow Homer, Paul Signac, Georgia O’Keeffe and Emil Nolde.
Ochre
Family of earth pigments containing iron oxide, ranging in colour from yellow to red and brown. Natural ochres are among humanity’s earliest colouring materials, valued for their stability, availability and non-toxicity. Used since prehistoric cave painting, ochre has been found in Paleolithic sites such as Lascaux and Altamira. Throughout history, it remained a staple pigment in fresco, tempera and oil painting.
Canvas
A tightly woven fabric, traditionally made from linen or hemp and later from cotton, used as a support for painting. It is typically stretched over a wooden frame called a stretcher or strainer and primed with gesso or a similar ground to prevent the paint from soaking into the fibres. Canvas became the dominant painting surface in Western art from the 16th century onwards, replacing wooden panels for its lighter weight, flexibility and portability. The use of canvas began in Venice, where the humid climate made wooden panels prone to warping. Venetian painters such as Titian and Tintoretto popularised its use. By the 17th and 18th centuries, canvas had become the standard support for oil painting across Europe.
Ground Layer
A preparatory coating applied to a support such as canvas, wood panel or plaster before the application of paint. It creates a smooth, stable and absorbent surface, improving the adhesion of pigments and influencing the colour and texture of the finished work. Grounds can range from traditional chalk and glue gesso to modern acrylic formulations. Artists often choose warm or cool tones for the ground to affect the overall composition. The practice dates back to antiquity, with variations seen in Egyptian panels, medieval tempera paintings and Renaissance frescoes. During the Renaissance, artists such as Leonardo da Vinci and Raphael used carefully prepared gesso grounds to produce luminous, seamless surfaces. Later painters like Rembrandt and Vermeer experimented with tinted or layered grounds to control light and enhance depth.
Above: detail from an oil painting on panel with extensive craquelure
Panel
A wooden board used as a support for painting. Panel paintings were typically composed on well-seasoned hardwoods such as poplar, oak or walnut. They were prepared with layers of gesso to create a smooth, white surface for tempera or oil painting. They allow for a fine painting texture, though they are heavier and more prone to cracking than canvas. Panel painting was the dominant method in medieval and early Renaissance Europe, used for altarpieces, devotional works and portraits. Northern European artists favoured oak, while Italian painters often chose poplar due to local availability. With the rise of oil painting in the 15th century and the demand for larger, more portable works, canvas gradually replaced panels, especially in Venice and Flanders.
Craquelure
A fine network of cracks that naturally develops on the surface of paintings, varnish layers or other coated materials over time. These painting cracks form as a result of ageing, environmental changes and the mechanical stresses between paint, ground and support layers. Craquelure can appear in different patterns depending on the materials used, the artist’s technique and the history of the artwork. While sometimes perceived as a flaw, craquelure is often considered a hallmark of age and authenticity. Conservators study the type, depth and direction of cracks to understand an artwork’s condition, materials and history. Stable craquelure poses no threat, but active or widened cracks may signal structural instability or environmental stress.
Ultramarine
Deep blue pigment originally made by grinding the semi-precious stone lapis lazuli, mined primarily in Afghanistan. Renowned for its intense, luminous hue and permanence, ultramarine was historically one of the most expensive pigments. Modern synthetic ultramarine offers a chemically identical but more affordable alternative. Used since the Middle Ages, ultramarine was reserved for the most sacred or prestigious areas of paintings — particularly the robes of the Virgin Mary. Synthetic ultramarine was discovered by Jean-Baptiste Guimet in 1826, revolutionising access to the colour for artists.
Grisaille
A painting executed entirely in shades of grey or neutral tones to imitate the appearance of sculpture or to serve as a monochrome underpainting. Derived from the French word gris meaning “grey” the grisaille technique emphasises form, volume and light without the distraction of colour. Grisaille may be used as a preparatory study or as a finished form. The technique emerged in medieval manuscript illumination and stained glass, where artists simulated relief sculpture. Jan van Eyck used grisaille in the Ghent Altarpiece and Giotto and Masaccio applied the technique to architectural fresco details. Peter Paul Rubens created dramatic grisaille oil sketches for large altarpieces and Jean-Auguste-Dominique Ingres used it for compositional studies. In the 20th century, artists such as Pablo Picasso revisited grisaille in works like Guernica, using tonal restraint to produce emotional power.
Above: detail from Odalisque in Grisaille by Jean Auguste Dominique Ingres, 1824-34
Pigments
Natural or synthetic coloured powders that provide the hue and opacity of paint, ink and drawing media. When mixed with a binder, they form a stable medium such as oil, tempera, watercolour or acrylic. Pigments may be derived from minerals, plants or animal sources. In modern art they may be created from from chemically engineered compounds. Their lightfastness, transparency and toxicity vary greatly, influencing both the artist’s choice and a painting’s long-term preservation. Pigments have been used since prehistoric cave painting, when ochres, charcoal and earth minerals formed the earliest colours. By the Renaissance, artists had access to a wide palette, including rare and costly materials such as ultramarine (from lapis lazuli) and vermillion (from cinnabar). The Industrial Revolution introduced mass-produced and synthetic pigments such as Prussian blue, chrome yellow and later cadmium and titanium white.
Binder Medium
The component in a paint that suspends pigment particles and binds them, allowing them to be applied to a surface. The binder determines a paint’s handling properties, drying time, finish and long-term stability. Since antiquity, artists have used various natural substances as binders including animal glue, egg yolk, beeswax, gum arabic and plant oils. Each binder gives paint its distinct character: tempera is matte and durable, oil produces depth and flexibility, gum arabic creates transparent watercolours and modern acrylic polymers allow for a vibrant, fast-drying finish. The evolution of binders reflects both artistic innovation and advances in chemistry.
Stretcher / Strainer
Structural wooden frames used to support a canvas or textile painting surface. A stretcher is an adjustable frame, joined at the corners with expandable keys or wedges that allow the tension of the canvas to be altered over time. A strainer is a fixed wooden frame without such adjustment, used before the invention of keyed stretchers in the 18th century. Both serve to hold the canvas taut and flat, ensuring a stable painting surface.
Vermilion
Also called Cinnabar, this is a brilliant red pigment derived from mercury sulfide (HgS) either naturally occurring as the mineral cinnabar or artificially produced by heating mercury and sulfur. Known for its opacity and intense warmth, vermilion has been used in painting, manuscripts and lacquerware for over two millennia. First used in ancient China and later throughout Rome and medieval Europe, vermilion was a prized but costly pigment. It was highly toxic due to its mercury content, leading to the development of safer red pigments in the modern era.
Above: detail showing the use of vermilion in The Annunciation by Hans Memling, 1465-70
Lead White
Dense, opaque white pigment made from basic lead carbonate. Known for its warm tone and fast-drying properties in oil, it was the primary white pigment in European painting for over 500 years. The production of lead white involved exposing lead to vinegar vapours and carbon dioxide. Its toxicity has led to its replacement by safer alternatives in the 20th century, when zinc and titanium white became substitutes.
Scumble
A thin, opaque or semi-transparent layer of paint lightly brushed or rubbed over a dry layer of colour to modify its tone, texture or luminosity. The technique softens transitions, reduces intensity and creates atmospheric or misty effects by allowing parts of the underlying colour to remain visible through the upper film. Scumbling is often achieved with a dry brush or rag and is typically used in oil or acrylic painting, though the principle also applies in pastel and other media. The scumbling technique developed during the Renaissance and is seen throughout the history of art up until the contemporary period.
Pentimento
The visible trace or reappearance of an earlier design, drawing or composition beneath a layer of paint. The term derives from the Italian pentirsi, meaning “to repent” referring to the painter’s “repentance” of an earlier idea. Pentimenti may emerge over time as upper paint layers become more transparent with age or through modern imaging techniques such as infrared reflectography. Famous examples of pentimento include Leonardo da Vinci’s Virgin of the Rocks with changes in the position of hands and Johannes Vermeer’s Girl with a Pearl Earring which shows a faint outline of a necklace that was later painted over.
Above: an example of verdigris applied as the background from the workshop of Quinten Massys
Verdigris
Blue-green pigment produced by corroding copper or bronze with acetic acid. Verdigris was prized for its bright hue, however it was unstable and prone to darkening or reacting with other pigments.
Isinglass
Fish-derived adhesive or sizing material traditionally obtained from the dried swim bladders of sturgeon and other fish. When dissolved in warm water, it forms a clear, flexible gel used as a binder, consolidant or sizing agent in both artistic production and art conservation. Isinglass is prized for its transparency, reversibility and strong adhesive properties, making it ideal for delicate and ethical painting restoration treatments. Owing to its purity and lack of discolouration, it is often favoured over animal glues.
Underpainting
Monochrome or limited-colour base layer applied to a support to establish the composition, tones and general structure of a painting before the application of final colours. It serves as the foundation upon which glazes and opaque paint layers are built, helping the artist to define light, shadow and spatial relationships early in the process. Underpaintings are typically executed in neutral or earthy tones and may remain partially visible through subsequent layers, contributing to depth and luminosity. The practice of underpainting dates back to antiquity. During the Renaissance, artists used tonal studies such as grisaille (grey monochrome) and verdaccio (greenish brown) to model form and flesh tones. By the 19th century, Impressionist and modern artists began to adapt or omit underpainting in favour of direct colour application, known as alla prima.
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