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Glossary

A

Additive colour combination
Combination of different spectral colours, i.e. light of different colours (as opposed to the material colours used in painting); when combined, the additive primary colours yield white. The additive primaries are (orange-)red, green and (violet-) blue (RGB).

alla prima (It.), au premier coup (Fr.)
Term meaning "at the first go," used to indicate a painting technique in which the painting is completed in a single sitting; the concept of "alla prima painting," derived from this, is the opposite of the layered painting technique, in which the individual layers of paint and glaze are applied successively, one over the other.

Artists' board
>board

B

Binder, binding agent
Liquid medium that binds the paint (pigments, lakes) and in principle possesses drying properties; in Impressionist painting the most significant binding agents were linseed oil, poppy-seed oil and walnut oil.

Board
Several layers of paper are glued or pressed together to create cardboard, which is known as artists' board (or simply "board") when prepared as a picture >support; from the middle of the 19th century it could be found in art supply shops >primed or unprimed, later also as the backing for a >pre-primed fabric.

C

Canvas
A textile picture >support.

Coloured shadows
Optical phenomenon that primarily occurs on neutral-coloured backgrounds such as white snow or the walls of houses; in combination with direct sunlight, reflected light or scattered light, half-shadows are created whose tone appears complementary to the colour of the light (given an appropriate angle of incidence, yellow-orange sunlight can produce blue half-shadows).

Complementary colours, complementary contrasts
Term for colours that lie opposite one another on the >colour wheel and when combined as >spectral colours result in white, and as >material colours in black; when complementary colours are contrasted they appear stronger and brighter; the effect of complementary contrasts acquired great significance in the painting of the Impressionists.

Cradle, cradling
A reinforcement of a wood picture support, consisting of thin interwoven wooden slats.

croquis (Fr.)
First, drawn compositional sketch, mostly consisting of a few rapid lines.

Cross-section
Samples of the ground and paint layers (max 1 mm) embedded in artificial resin, which are taken from a plane perpendicular to the layers. Microscopic observation of cross-sections provides important information on the stratigraphy of the work, i.e. the structure of the layers of ground and paint. Cross-sections can also be assessed under the stimulation of UV radiation and used for further examinations.

D

Divisionism
Division or spatial separation of the colour values; with the application of pure colours that are "decomposed," in other words separated from one another, the goal was to achieve a particular luminosity and chromatic effect in the beholder's eye; >Pointillism developed from Divisionism.

Dye
Soluble substance that can colour other materials; the original range of dyes derived from plants (e.g. saffron) and animals (e.g. the cochineal insect) was greatly extended in the 19th century through the creation of synthetic dyes (e.g. aniline).

E

ébauche (Fr.)
>Underpainting, which was carried out on the final picture >support, and sets chromatic rather than compositional accents.

EDX (Energy Dispersive X-ray microscopy)
EDX is a technique for determining the elements present in a sample. The atoms in the sample are stimulated to emit X-rays with an energy specific to each element.

esquisse (Fr.)
A painted compositional study, which develops the drawn compositional sketch in colour, albeit in a significantly smaller format than that of the subsequent painting.

étude (Fr.)
Study, also frequently a study of details painted from nature or from a model.

F

Foldover
When a >canvas is attached to a >stretcher, the foldover is the outside edge of the canvas that projects beyond the stretcher and is folded over and tacked down.

False-colour infrared
A photographic technique which reproduces the colours of an object completely differently, hence the name. It was originally based on film material sensitive to infrared, but also to red down to green. Today false-colour photographs are as a rule created digitally, and can be helpful in the characterization of pigments and later revisions.

Fourier Transform Infrared Spectroscopy (FTIR)
FTIR is an established spectroscopic method in painting analysis. It allows the identification of numerous components in a paint sample, enabling in turn important conclusions to be drawn in respect of pigmentation, filler substances and binding media. The signals are converted into transmission spectra which can be evaluated.

G

Glaze
Semi-transparent application of paint.

Ground
White, tinted or coloured coating which prepares a picture >support for the actual painting; the purpose of the ground is to even out the irregularities of the support, to ensure that the layers of paint bind with the surface, and to influence the final appearance of the painting through its thickness, colour, and surface finish.

I

Impasto
From impasto = "dough" (Ital.); a viscous application of paint, resulting often in a relatively thick layer.

Impression
Apart from its standard meaning in English, the term was used in 19th-century France to indicate the >ground of a painting >support and also the coats of paint applied to walls in buildings.

Incident light
Even illumination perpendicular to the picture plane under daylight-similar conditions, cf. >raking light >transmitted light

Infrared reflectography/infrared reflectogram
An investigation technique in which infrared rays penetrate the >paint layer and can reveal, in particular, hidden >underdrawings on a light >ground; the infrared reflectogram is the visible result of infrared reflectography.

L

Lake
An organic dye of natural or synthetic origin that must be bound with a solid, usually a mineral salt, by precipitation or other means, in order to make it available for use as a water-insoluble >pigment.

Layering technique
With the layering technique, individual applications of paint and >glaze are layered over previous ones, often influencing the colour of the layers beneath them.

Lining
Process in which a fresh >canvas is stuck on to the entire >verso of the original painted canvas >support, with a view to re-inforcing it.

M

Material colours
In optics, >spectral colours are distinguished from "tangible" material colours, i.e. the colours of >pigments, >dyes, paints etc.

Microchemical techniques
Microchemical techniques are used predominantly to identify inorganic, mineral components (e.g. pigments). The identification is done as a rule under the microscope, evidential reactions being carried out with the addition of reagents on individual substances contained in the paint sample. These reactions are based on characteristic colour changes, crystal formations or on a conspicuous decomposition of the sample (e.g. with gas development).

O

Overpainting
Covering a surface with paint.

P

Palette
A flat, wooden board, generally with a thumb-hole, upon which the paints can be placed and mixed.

Pentimento (pl. pentimenti)
From the Italian for "remorse"; in many languages a common term in painting referring to modifications that could take place during any stage of the artistic creation, from the >underdrawing to the final applications of paint; pentimenti can be revealed by various investigative techniques (see x-ray, infra-red reflectography).

Pigment
Usually a solid colourant (as opposed to >dye, which is liquid, or in solution), which, together with a >binding agent (e.g. linseed oil) composes the paint; pigments can be created from natural ingredients (e.g. earth pigments) or artificially (e.g. cadmium yellow).

Plein air
The French term en plein air means "in the open air," "outdoors"; plein air painting refers to painting done outdoors, which gained great significance in the art of the Impressionists.

Pointillism
From the French word, point, "dot", a term for a painting technique in which the paint is applied in separate dots of pure colour, rather than mixed on the >palette; this style gained significance in Neoimpressionism in connexion with the spatial decomposition of colours (>Divisionism).

Pre-priming, pre-primed
Larger lengths of canvas >primed before being cut to size and >stretched are said to be pre-primed; the >ground would then extend to the outer edge of the >foldover.

Primary colours
See >subtractive colour combination, >additive colour combination.

Priming, to prime
Priming is a synonym for >ground; to prime is to apply a ground.

Provenance
The "pedigree" of an artwork; a chronological list of owners preferably unbroken and ideally leading back to the artist.

R

Radiography
Radiography is the creation of images of a body which is being penetrated by X-rays. As the materials in a painting (e.g. pigments, especially lead white) are differently opaque to X-rays, radiography can allow conclusions to be drawn in respect of layering, revisions and restoration measures.

Raking light
Light striking the surface of the object obliquely or parallel to its plane, revealing surface structures (e.g. impasto application of paint) more clearly.

Recto
The front or visible side of a picture >support or frame (see >verso).

Reflected light
Reflections and shine are usually avoided when photographing paintings. The reflections obtained by targeted frontal illumination clarify structural and shine differences in the surface.

Retouching
In painting, selectively covering certain areas with paint after the painting is otherwise complete is known as retouching; of the utmost significance is the distinction between retouching carried out by the artist him/herself to improve the painting and retouching carried out by other hands.

S

SEM (Scanning Electron Microscope)
The scanning electron microscope allows the detailed representation of the surface of a sample. A beam of electrons is scanned over the sample and the interactions of the electrons with the object are used to create an image of the surface. The image is characterized by its particular high depth of focus and a high magnification factor (up to app. 1,000,000:1).

Simultaneous colours, simultaneous contrasts
Simultaneous contrast strengthens the brightness and colour differences, as our sight organs always perceive in relation to their environment; the same colour surface seen simultaneously against a white and black background as opposed, for example, to a yellow and green background produces a different colour effect in us.

Sizing
A term for the insulating layer of size or glue applied before the actual >priming in order to reduce the absorptive properties of wood, canvas and board >supports.

Spectrum, spectral colours
When white light is shone through a prism it produces the familiar spectrum of violet, indigo, blue, green, yellow, orange and red, known as spectral colours.

Standard format, standard size
A standard system developed in France for picture formats; it covered not only the actual dimensions, but also genres (portrait, landscape, seascape) and was applied to all commercial painting supports; picture dimensions from a height of 12 to 130 cm and a width of 22 to 195 cm were numbered from 1 to 120.

Stereo-microscopy
A microscopic technique which permits a three-dimensional view of the object, in our case with a magnification of up to 90fold. Stereomicroscopy can be used to obtain detailed information on painting materials and techniques, as well as the sequence of the application, and also of a painting's state of preservation.

Strainer
A >stretcher without keys and hence unadjustable.

Stretcher
Frame construction to which the >canvas is fastened or "stretched"; the wedges (or "keys") in the corner joints make it possible to adjust the tension on the canvas; the stretcher frame was introduced around the middle of the 18th century and increasingly replaced the older >strainer.

Subtractive colour combination
Term for the combination of >material colours (as opposed to >spectral colours), which subtracts rays of light and ultimately yields black; the subtraction occurs because more >spectral colours are absorbed as further >pigments or >dyes are added; subtractive colour combination occurs therefore when paints are mixed; the primary colours in subtractive colour combination, which combine to yield black, are traditionally yellow, blue and red; in modern printing, they are cyan (blue-green), magenta (purplish-red) and yellow (CMY).

Support
The physical surface on which a picture is painted; during the Impressionist period, >canvas, >wood panel and artists' >board were the most important supports. tableau in the terminology of French academic painting, the finished picture, as opposed to sketches and studies.

T

Transmitted light
The painting is illuminated from behind. The translucency of different areas varies according to the thickness and density of the ground and the paint layers, allowing further characterization of the painting technique.

Ultraviolet (UV) fluorescence
Fluorescence is an optical phenomenon, applied in the examination of paintings, which is generally caused by the stimulation of short-wave ultraviolet rays and primarily provides information regarding >varnishes, >retouching and >overpainting.

Underdrawing
Drawn compositional layout on the >ground which is subsequently to be painted, as opposed to the preparatory drawing, which is created on a separate >support.

Underpainting
The first applications of paint, which are partially or completely covered by successive layers (see >ébauche).

V

Varnish
A transparent colourless or sometimes tinted lacquer-like coating based on dissolved resin; part of the standard process for the completion of a painting until c. 1870; from the French, vernis, the term >vernissage is derived, which originally described the act of varnishing and later became synonymous with the opening of an exhibition.

Vernissage
>varnish.

Verso
The reverse or back of a picture >support or frame (see >recto).

VIS spectrometry
This method allows a non-destructive measure of colour. In comparison with standard references, detailed conclusions can be drawn in respect of the pigments used (Link Oltrogge)

W

Wet-in-wet
Painting technique in which a wet paint application is deliberately applied to a still wet layer and mixed with it to a certain extent in order to create, for example, intermediate tones.

Wet-on-dry
Painting technique in which single or multiple >paint layers are applied to an already thoroughly dry paint layer.

Wet-on-wet
Painting technique in which paint is applied to a still wet or moist layer, but which is not intended to produce colour mixing. wood the oldest >support for easel painting, only seldom used by the Impressionists; in the French painting supply shops of the 19th century, the most popular woods were tropical red-brown mahogany followed by the pale softwood varieties, including poplar, linden, fir and tropical tulipwood.

Wood identification
Types of wood can be identified by microscopic observation of the various kinds of cell and cell groupings, in respect of their size, quantity and distribution. The procedure requires the taking of a material sample whose structures are examined on the transverse, radial and tangential surfaces at magnifications ranging from 40 to 400fold.

X

X-ray examination
An x-ray examination of a painting, i.e. in practice a photograph taken with x-rays rather than visible light, can be useful because certain >pigments (above all lead white) are highly opaque to x-rays; this can provide information about layering, >pentimenti and past conservation measures.