Glossary of Italian gold-ground painting

Essential terminology for the study of panel painting iconography, technique & historical context.

Abrasion — Tech.

Surface damage caused by repeated contact with another material, gradually wearing the paint layer away. On a panel painting, abrasion typically appears as scattered small losses that expose an underlayer, disrupting how a passage reads: modelling flattens, forms break up, and the paint can look thinner than it was ever intended to be. Aggressive past treatments are the usual cause — harsh cleaning with strong solvents, or excessive mechanical action during earlier conservation campaigns.

Alla Prima — Tech.

Working fresh paint into underlayers that are still wet, also called wet-in-wet. The paint must be stiff-bodied and remain open long enough to be manipulated; successive strokes are driven into the lay-in with a bristle brush, often leaving multi-coloured swirls of impasto. Fast to execute, prized for spontaneity.

Altarpiece — Object

A devotional work placed upon or behind an altar, typically a painted panel or series of panels. Gold-ground altarpieces dominated Italian churches from the late Duecento through the early Quattrocento, conveying the sacred presence of holy figures to the faithful.

Ancona — Object

A type of altarpiece, often with a cusped or pointed upper profile, associated with the Veneto and Adriatic regions. Anconae frequently feature the Virgin and Child enthroned under gilded Gothic architectural canopies.

Archivolt — Tech.

The ornamental moulding running around the outer curve of an arch in panel frames. In gold-ground polyptychs, archivolts are often punched or incised with foliate and geometric patterns that catch candlelight.

Assisting — Tech.

The technique of applying thin lines or hatching of gold leaf (or occasionally silver) over drapery to indicate divine light or celestial sheen, most notably in the draperies of Cimabue and early Duccio.

Aureole — Tech.

A full-body nimbus or mandorla-shaped radiance surrounding the entire figure of Christ or the Virgin in scenes of the Transfiguration, Ascension, or Last Judgement, typically rendered in burnished gold leaf.

Baldachin — Tech.

A canopy of honour depicted above enthroned figures in panel painting, often rendered in tooled gold to create a three-dimensional architectural illusion within a two-dimensional gilded space.

Battiloro — Tech.

A gold-beater, the craftsman who beat gold alloys into the ultra-thin sheets used as gold leaf. The quality of a battiloro's work directly determined the reflective quality of the fondo oro ground.

Biacca — Tech.

Lead white (basic lead carbonate), the primary white pigment used in Italian panel painting. Mixed with egg tempera, biacca was layered over black underdrawing to model flesh and highlights.

Binder — Tech.

Paint consists of dry pigment particles dispersed in an adhesive substance, the binder or medium. Aqueous binders include animal glues and gums, used for ephemeral works and for painting on fine linen (tüchlein), as by Justus van Ghent, Dürer, and Mantegna. Early Italian painters bound panel paintings in egg yolk, and used beaten egg white — glair — for manuscript illumination. Northern European painters favoured drying oil for its translucence and the ease with which it could be blended toward naturalistic effect; oil was taken up in Italy from the later fourteenth century onward. The two principal drying oils are linseed, which sets faster but yellows with age, and walnut, slower to dry, more fluid in handling, and far less prone to yellowing. Driers, volatile oils, and resins could be added to modify the binder's behaviour. Unlike aqueous media, which dry by evaporation, drying oils polymerise over time into a tough, durable film.

Bole — Tech.

A reddish-brown or ochre-coloured clay ground applied over gesso as the final preparatory layer before gold leaf is laid. The warm tone of Armenian bole ensures that any gaps in the gold appear as a warm, sympathetic hue rather than a stark white.

Burnishing — Tech.

The process of polishing laid gold leaf with a hard, smooth tool — traditionally a dog’s tooth, agate, or hematite — to produce a mirror-bright, reflective surface. Burnished gold creates the luminous, otherworldly background characteristic of the fondo oro tradition.

Cennino Cennini — Painter and author

Florentine painter (c. 1360–c. 1427) and author of Il Libro dell’Arte (c. 1400), the most important surviving technical manual of medieval Italian painting. Cennini’s detailed instructions on gesso preparation, gilding, tempera mixing, and gold tooling are an indispensable primary source for the fondo oro tradition.

Ciborium — Tech.

A container for the Eucharist host, but in art history also a canopied baldachin over an altar. The ornamental form influenced the canopy motifs tooled into gold grounds of altar panels.

Cleaning — Tech.

The removal of non-original surface coatings and accretions from a painting. In paintings conservation, "cleaning" ordinarily denotes the removal of varnish and/or overpaint, carried out with volatile solvents, gels, poultices, or mechanical means. "Surface cleaning" is the narrower operation: removal of dirt, soot, smoke, and other deposits by dry or aqueous methods, without disturbing the varnish layer.

Cradle — Tech.

A wooden lattice attached to the reverse of a panel painting to restrain warping along the grain. Developed in eighteenth-century France from the earlier practice of setting cross-battens into grooves cut in the panel, cradling was applied widely through the nineteenth and early twentieth centuries to panels that were worm-tunnelled, distorted, or split.

The procedure was invasive. The original panel was thinned, splits re-glued, and weakened areas cut out and inlaid with new wood; moisture was applied to the reverse to swell the cells so the panel could be flattened; notched slats were then glued along the grain and the assembly dried under press. Unglued cross-members were slid through the notches, and in a well-made cradle these were free to move, permitting the panel to expand and contract with changes in relative humidity.

Wood remains hygroscopic long after the tree is felled. In an unstable environment the panel moves while the cross-members seize, and the restrained wood splits or the ground and paint layers buckle under compression. Cradles are now frequently removed and replaced with flexible auxiliary supports that let the panel expand, contract, and even warp slightly.

Craquelure — Tech.

The network of fine cracks that develops over centuries in the gesso and paint layers of a panel painting. Distinctive crack patterns assist connoisseurs in dating and attributing gold-ground works and in distinguishing original surfaces from later restorations.

Cross-section — Tech.

A minute sample taken from a painting and embedded in synthetic resin. Once cured, the resin block is ground back with successive abrasives until the sample is exposed in section, revealing its stratigraphy: ground, priming, underdrawing, paint layers, and surface coatings. The section is examined under the microscope in visible and ultraviolet light, which establishes the sequence and thickness of the layers and allows many pigments to be characterised by colour, particle size, and morphology. Its particular value is positional: a cross-section fixes a material at a specific depth within the stratigraphy, which elemental methods applied to the surface cannot resolve.

Cusping — Tech.

Decorative pointed projections forming trefoil, quatrefoil, or multilobed arches above individual figures in polyptych panels. Cusped frames are a hallmark of the Gothic style that transformed Florentine and Sienese altarpieces from the 1280s onward.

Dendrochronology — Tech.

The dating of timber by its growth rings, whose widths vary with seasonal climate and produce a pattern that can be matched against regional master chronologies. Applied to panel supports, the method is largely confined to oak, and it yields only a terminus post quem: the outermost surviving ring gives the earliest possible felling date, to which an estimate for the missing sapwood must be added, since panel makers cut it away. Further time then elapsed in seasoning and in the workshop's timber store before the plank was worked. The other woods common in panel painting — poplar, linden, cypress, walnut, fruitwoods — cannot usefully be dated this way, either because no master chronology exists or because their ring structure is too irregular to match.

Deësis — Gk. déēsis

An iconographic composition in which the Virgin Mary and St John the Baptist flank Christ in intercessory prayer, originating in Byzantine art and appearing frequently in the upper registers of Florentine and Sienese polyptychs.

Diaper Pattern — Tech.

A repeating geometric or foliate motif, incised or punched into the gold ground to create a textured field behind figures. Diapers activated the gold surface, preventing the flat reflection from dominating the painted image.

Diptych — Gk. diptychos

A devotional work consisting of two hinged panels. Portable diptychs — often small, with ivory or wood wings — were a common private devotional format in fourteenth-century Italy, produced by painters from Tuscany to the Veneto.

Engaged frame — Tech.

A frame integral to the panel rather than fitted around it afterwards — characteristic of Early Italian painting, particularly in Tuscany. The panel maker attached the decorative moulding to the flat support with glue and nails (occasionally carving it from the plank itself), and the ground was then brushed over the whole assemblage. The moulding received fewer coats, and of gesso sottile only, so that the carving would not be blunted.

When altarpieces were later dismantled and their compartments separated, the mouldings were commonly prised away. What remains is a raised ridge of gesso along the edge of the painted field — the barbe, from the French for beard — together with a reserve of bare wood beyond it where the moulding had sat. The presence of a barbe is strong evidence that the field has not been trimmed, and its absence on one side of a panel is often the first indication that a compartment has been cut from a larger structure.

Egg Tempera — Tech.

The primary binding medium of Italian panel painting before the adoption of oil. Pigments were ground and mixed with egg yolk (and occasionally egg white or the whole egg) to produce a fast-drying, luminous, and highly stable paint film compatible with gold-ground grounds.

Encaustic — Tech.

An ancient painting technique using pigments bound in hot wax, practised in Byzantine icon production and occasionally studied by medieval artists seeking to emulate Greco-Roman models. By the Duecento it had been largely supplanted by egg tempera in Italy.

Flabellum — Lat.

A liturgical fan used during the Mass to protect the Eucharist. Representations of angels holding flabella appear in late Duecento and Trecento Florentine panels as markers of celestial liturgy.

Fondo Oro — It.

Literally ‘golden ground’: the burnished gold-leaf background that defines the tradition of Italian panel painting c. 1250–1430. The gold ground functions not as a naturalistic sky but as a sacred space — the uncreated light of the divine realm.

Fresco — Object

Mural painting on freshly applied wet plaster (buon fresco) or dry plaster (secco). Although distinct from panel painting, fresco iconography — especially in Giotto’s Arena Chapel cycle — profoundly influenced the spatial ambitions of Trecento gold-ground masters.

Gesso — Tech.

A mixture of calcium sulphate (gypsum) or chalk bound in animal-skin glue, applied in multiple coats to a wooden panel to create a brilliant white, smooth ground for painting and gilding. Gesso grosso (coarse) and gesso sottile (fine) were applied in succession.

Glue Size — Tech.

A dilute solution of animal-hide glue applied to the wood panel before the gesso layers, sealing the grain and providing a key for subsequent coats. Without correct sizing, gesso would absorb unevenly and gold leaf would not adhere.

Gold Leaf — Tech.

Extremely thin sheets of beaten gold, typically 22–24 carat, applied to the bole-covered gesso with dilute glue size or glair (beaten egg white). Standard sheets in Cennini’s time measured approximately 3½ × 3½ inches.

Gothic — Arch.

The Northern European architectural and decorative style, adopted in Italian panel painting from c. 1270–80, characterised by pointed arches, ogival forms, cusping, and elaborate carved frames. The Gothic style shaped the formal language of Florentine and Sienese gold-ground altarpieces throughout the Trecento.

Halo (Nimbus) — Tech.

The circular disc of gold leaf surrounding the head of a holy figure, signifying divine or saintly status. Haloes were tooled, punched, or incised with decorative patterns, and their elaborate treatment was a primary vehicle for the goldsmith’s art within panel painting.

Hieratic Scale — Art H.

The convention of representing sacred figures at a size proportional to their spiritual importance rather than their physical distance from the viewer. Christ, the Virgin, and major saints appear significantly larger than secondary figures in Italian gold-ground panels.

Impasto — Tech.

Paint applied thickly enough to stand proud of the surface and hold the mark of the tool that laid it down. Depending on the consistency of the paint, impasto ranges from a slight raising of the surface to pronounced ridges and peaks worked up with a stiff brush or knife.

Imprimatura — Tech.

A thin, transparent toning layer applied over the gesso ground before painting, used to unify the surface and reduce the stark whiteness of the preparation. In tempera technique, an imprimatura of terre verte was standard for flesh underpaint.

Incising — Tech.

The technique of scratching or engraving linear designs into the bole and gold leaf surface with a stylus or burin. Incised patterns activated the gold ground with light-catching lines and created architectural details, fabric patterns, and decorative borders.

Infrared reflectography — Tech.

An imaging technique exploiting the fact that most pigments become increasingly transparent at infrared wavelengths, while carbon-based materials continue to absorb. Infrared radiation passes through the upper paint layers, is absorbed by carbon-containing underdrawing, and is reflected back by a light-colored ground, so that the drawing registers as dark against a pale field. Introduced in the late 1960s, the method was first applied with striking success to Early Netherlandish panels. Detectors sensitive across a wider infrared range, with improved resolution, now also disclose pentimenti, underpainted sketches, and compositional changes, including on panels with darker grounds. Captures are made in segments as the camera traverses the surface and digitally assembled into a reflectogram.

International Gothic — Style

A courtly, elegantly decorative style that flourished across Europe c. 1380–1430, characterised by sinuous line, jewel-like colour, naturalistic detail, and elaborate gilded ornament. In Italy it is associated with Gentile da Fabriano, Pisanello, and Michelino da Besozzo.

Kolophonium (Rosin) — Tech.

Pine resin occasionally used in varnishes applied over finished gold-ground panels to protect the paint surface and saturate colours. Its yellowing over centuries complicates the reading of original tonalities in conservation.

Maestà — Subject

A composition showing the Virgin enthroned in majesty (maestà) surrounded by angels and saints, the dominant devotional image of Florentine and Sienese altarpieces. Duccio’s Maestà for Siena Cathedral and Cimabue’s for Santa Trinità, Florence, are its canonical expressions.

Mandorla — Tech.

An almond-shaped aureole enclosing the full figure of Christ or the Virgin in scenes of the Transfiguration, Ascension, or Last Judgement. Usually rendered in concentric rings of burnished gold shading to lighter, more silvery tones toward the figure.

Mastic (Mastice) — Material

A natural resin from the mastic tree (Pistacia lentiscus) used in varnishes and as a medium modifier. Its inclusion in gold-ground panel varnishes was noted by Cennini as a way to produce a glossy, protective finish.

Mordant Gilding — Tech.

A technique in which gold leaf is applied over a sticky adhesive (mordant) rather than over bole and water gilding, used for intricate applied ornament on frames, textiles, and architectural details where the matt, non-burnishable finish is acceptable or desired.

Niello — Tech.

A black sulphide of silver, copper, or lead inlaid into engraved metal to create decorative patterns. The fine linear ornament of niello work influenced the incised decoration of gold grounds and gilded frames in Tuscan panel painting.

Overpaint — Tech.

Non-original paint applied over the artist's own work rather than confined to areas of loss — the distinction that separates it from legitimate retouching. Overpaint is frequently old, often predating the most recent campaign, and its media may have cross linked to the point where removal is slow and hazardous. It was applied for various reasons: to bring a passage into line with a restorer's idea of how it should look, to suppress elements of a composition thought undesirable, or to conceal damage rather than repair it. Because it commonly extends well beyond the damage it was meant to address, sound original paint is often recovered when it is removed.

Pala d'Altare — Object

The Italian term for a large altarpiece, particularly an integrated single-surface panel (as opposed to a polyptych with divided sections). The unified pala emerged in the mid-Trecento and became standard by c. 1400, partly under the influence of monastic Dominican altarpieces.

Panel — Tech.

Wood was the principal support for painting until the early sixteenth century, when canvas began to displace it. In Northern Europe panels were usually oak — hard, resistant to woodworm, and among the most durable supports to survive; northern panels are correspondingly thinner and often have a bevelled edge. Their manufacture was regulated by guild statute in Germany and the Netherlands, and panels passing inspection in Antwerp were branded with a mark. Oak is also the wood most reliably dated by dendrochronology, though the result is a terminus post quem rather than a felling date, since the sapwood was cut away in construction.

In Southern Europe the range is far wider. Poplar predominates in Central Italy, but walnut, clear pine, cypress, willow, linden, maple, and fruitwoods have all been identified. Felled timber was left to season, often for a decade or more, and boards might then sit in a workshop store for an indeterminate period. Seasoning is only one factor in a panel's stability: much depends on how the trunk was converted — radially cut boards move far less than tangential ones — and species differ markedly in their susceptibility to insect attack.

Most planks were 20–40 cm (7 to 15 inches) wide, though boards as wide as 60–70 cm (23–27 inches) occur; thickness depended on width, generally running from 30 to 45 mm (1.18–1.77 inches). Larger supports were built up from several boards, joined edge to edge with casein adhesive and usually reinforced on the reverse with battens.

Pastiglia — Tech.

Raised ornament formed from a paste of gesso mixed with glue, applied in relief to panel surfaces and frames before gilding. Pastiglia creates three-dimensional haloes, textile patterns, and architectural mouldings that catch light dramatically over gold grounds.

Polyptych — Object

An altarpiece consisting of three or more hinged or framed panels, the standard format of major Florentine and Sienese altarpieces c. 1270–1400. The central panel typically depicts the Virgin and Child, flanked by saints on the wings.

Predella — Object

The horizontal narrative strip of small panels forming the lower register of a polyptych altarpiece. Predellas allowed painters to explore sequential narrative within the gold-ground format, often depicting scenes from the lives of the saints shown above.

Punchwork — Tech.

General terms for the decoration of water-gilded backgrounds by impressing patterns into the burnished gold. Incised lines were the earliest form of tooling; later work was carried out with punches — metal stamps bearing a shape cut into the tip — struck lightly with a special hammer made of strips of hide, so that the design was pressed into the gold. Motifs range from a simple indentation, and circles and half-circles of various sizes that could be combined into more elaborate patterns, to complete designs such as a rosette, star, or trefoil arch. Punching was frequently combined with incising.

Timing was essential. The bole and gold had to hold just enough moisture to take a clean impression: too damp and the punch sank in, too dry and it left only a shallow mark. The resulting texture gave sparkle to an already brilliant surface and animated it as candlelight shifted across the panel. Because individual punch tools were workshop property and their marks are effectively unique, punch profiles are among the most reliable evidence for grouping panels and reconstructing dismembered altarpieces.

Gilded surfaces were often further embellished with glazes or opaque paint, partly scraped away to expose the gold beneath in a pattern — the technique known as sgraffito, used above all for the brocaded textiles of robes and hangings. It was brought to a high pitch of refinement by Sienese painters of the fourteenth and fifteenth centuries, among them Simone Martini, Bartolomeo Bulgarini, and Giovanni di Paolo.

Quatrefoil — Tech.

A decorative form consisting of four equal lobes, used in the cusping of altarpiece frames and as a repeated motif in incised or punched gold grounds. The quatrefoil is one of the defining ornamental forms of Gothic Italianate painting.

Retable — Tech.

An altarpiece placed directly on or behind the altar table, the most common position for Italian gold-ground panels. The term is often used interchangeably with altarpiece in art historical literature.

Retouching (compensation — Tech.

Paint applied by a restorer to compensate for losses and damage that disturb the visual coherence of an image. Current practice requires that the materials be reversible and that retouching be confined to actual areas of loss; an accepted exception is made for passages abraded by past cleaning, where the final modelling layer is gone and thin glazes may be carried over original paint. The medium must not discolor with age and must remain readily soluble. Several are in use: dry pigments bound in stable synthetic resins or in egg tempera, and commercial formulations including watercolor, gouache, and paints made specifically for the purpose such as Gamblin Conservation Colors or Maimeri Restauro. Media are often layered one over another to approach the depth and enamel-like quality of the original surface.

Only stable pigments are used. Some historic colours are unsuitable — vermilion, for instance, is prone to alteration and is replaced by cadmium red — while others on the restorer's palette are identical to those the painter used. The retouching may be executed to be invisible at normal viewing distance or, in the Italian tradition of tratteggio, in fine parallel strokes that read as continuous from a distance but remain legible as restoration at close range.

Under ultraviolet light retouches appear as dark passages: they do not fluoresce, but reflect the violet light of the lamp against the fluorescence of the surrounding aged varnish.

Santa Conversazione — Subject

A compositional type depicting the Virgin and Child with saints informally grouped in a shared space, which gradually replaced the rigidly divided polyptych format from c. 1420 onward. The type represents a late, transitional stage of the gold-ground tradition.

Sgraffito — Tech.

In tempera painting, the technique of scratching through an upper paint layer to reveal the gold or lighter layer beneath, creating patterns of shining lines in draperies, architectural ornament, and haloes. Distinguished from incising, which scores the ground before painting.

Sinopia — Tech.

A red-ochre underdrawing, named after the ancient port of Sinope on the Black Sea from which the pigment was traded. In panel painting, an equivalent preliminary drawing in red or black defined figures before the application of paint.

Size — Tech.

A thin solution of rabbit- or calf-skin glue, applied warm to the panel before gessoing to seal the wood grain and prevent the gesso from cracking. See also: Glue Size.

Stilted Arch — Tech.

An arch whose spring-point is raised above the impost, producing a taller, narrower profile than a regular semicircular arch. Stilted arches appear frequently in the Gothic frame elements of Florentine and Sienese polyptychs.

Tempera — Tech.

The principal painting medium of the fondo oro tradition, in which dry pigments are bound in a water-miscible emulsion. Tempera dries rapidly by evaporation and is incompatible with oil, requiring deliberate layering of transparent glazes and opaque lights. See also: Egg Tempera.

Terre Verte — Tech.

Green earth pigment (celadonite or glauconite), widely used as an underpaint for flesh in Italian tempera painting. Its cool greenish tone created a chromatic balance with the warm bole of the gold ground and provided the shadows of modelled faces.

Throne (Trono) — Subject

The architectural seat upon which the Virgin or Christ is depicted in Maestà compositions. The throne evolved from a flat Byzantine bench toward an elaborate Gothic throne with inlaid marble and cushioned steps, reflecting both theological status and contemporary courtly furniture.

Trecento — History

The fourteenth century (literally ‘three hundreds’). The Trecento is the central century of the Italian gold-ground tradition, encompassing the work of Duccio, Giotto, the Lorenzetti, Simone Martini, Orcagna, and their followers.

Triptych — Object

A devotional or altarpiece work in three panels, hinged or fixed. The triptych format was enormously popular in fourteenth-century Italy and was produced at every scale, from portable private devotional objects to large church altarpieces.

Typos — Gk.

In Byzantine and early Italian theological discourse, a prefiguring image or type from the Old Testament that anticipates a New Testament antitype. The typological programme underpinning many gold-ground altarpieces reflected the exegetical theology of Dominican and Franciscan patrons.

Uffizi Gallery — Museum

The Galleria degli Uffizi in Florence holds the world’s greatest collection of Italian gold-ground panel paintings, including works by Cimabue, Duccio, Giotto, Simone Martini, and Gentile da Fabriano. Its rooms dedicated to the Duecento and Trecento constitute an essential reference for the field.

Ultramarine — Pigment

The most prized blue pigment of the medieval and Renaissance periods, produced from ground lapis lazuli imported from Badakhshan (modern Afghanistan). Its intense blue was reserved for the Virgin’s mantle in gold-ground panels as a signifier of her supreme status.

Ultraviolet Radiation — Tech.

Ultraviolet radiation, a wavelength on the electromagnetic spectrum shorter and more energetic than the visible light range, excites a characteristic fluorescence in many materials. Aged resins exhibit a greenish fluorescence, shellac looks orange, glue somewhat blue, and the fluorescence of certain pigments is so strongly colored that they can be identified without further scientific analysis. Red madder, for example, turns brilliant pink in UV light.

In conservation it is used to check the progress of varnish removal during cleaning, and to identify retouches.

Underdrawing — Tech.

Preliminary compositional lines drawn on the gesso surface (in ink, charcoal, or metalpoint) before painting. Infrared reflectography has revealed underdrawings beneath gold-ground panels that show pentimenti and compositional revisions invisible to the naked eye.

Verdaccio — Tech.

A greenish-grey underlayer used beneath flesh tones in Early Italian painting. Cennini's formula combines black, white, and yellow ochre, but the practice covers a wide range, from a distinctly cool green to a warm grey; the green cast often comes from terre verte rather than from a mixed neutral. The underlayer was laid in across the flesh areas and left to show through the thin, semi-transparent tempera modelling applied over it, cooling the shadows and half-tones. Cennini also specifies where the tone should be adjusted, advising that for an old man or a corpse the layer be darker and allowed to dominate.

Green underpainting for flesh persisted into the early sixteenth century, generally in egg tempera rather than oil. Highlights were carried on a pale, mint-toned ground and shadows on a warmer, darker green. Botticelli, Ghirlandaio, and Michelangelo continued to work in this system, and its effect is now often exaggerated, since the pink and white upper layers are frequently abraded, leaving the green more prominent than the painter intended.

Verdigris — Pigment

A copper-based green pigment (copper acetate), frequently used in fourteenth-century Italian panel painting for foliage, drapery, and backgrounds. Notoriously unstable, verdigris darkens or turns brown over time, distorting the original chromatic balance of many gold-ground panels.

Vermillion — Pigment

Bright red mercuric sulphide (cinnabar), one of the most vivid pigments available to medieval painters. Used for rich red draperies, architectural details, and inscriptions, vermillion provided strong chromatic contrast against the gold ground.

Water Gilding — Tech.

The standard gilding technique for fondo oro panels, in which gold leaf is picked up on a damp brush and laid onto a moist bole surface, then burnished when dry. Water gilding produces the brightest, most mirror-like surface of all gilding techniques.

Wilton Diptych — Object

An exceptionally refined portable diptych (c. 1395–99, National Gallery, London) with an English royal commission and gold ground, demonstrating the International Gothic synthesis of English, French, Italian, and Bohemian influences in gold-ground panel painting.

Xylography — Tech.

Wood-block printing, occasionally used to transfer repeating decorative patterns to frames and painted surfaces in the late Trecento. Stamped patterns extended the tooled decorative vocabulary of the gold-ground painter to printed paper and textile designs.

Zecca — History

A mint; the institution responsible for guaranteeing the purity of gold used in commercial transactions, including the gold alloys supplied to battilori for beating into leaf. The Florentine florin (fiorino d’oro), introduced in 1252, was the monetary standard against which the purity of painters’ gold leaf was measured.