Raking light, the illumination of objects from a

light source Light, visible light, or visible radiation is electromagnetic radiation that can be visual perception, perceived by the human eye. Visible light spans the visible spectrum and is usually defined as having wavelengths in the range of 400– ...

at an

oblique angle In Euclidean geometry, an angle can refer to a number of concepts relating to the intersection of two straight lines at a point. Formally, an angle is a figure lying in a plane formed by two rays, called the '' sides'' of the angle, sharing ...

or almost

parallel Parallel may refer to: Mathematics * Parallel (geometry), two lines in the Euclidean plane which never intersect * Parallel (operator), mathematical operation named after the composition of electrical resistance in parallel circuits Science a ...

to the surface, provides information on the

surface topography Surface finish, also known as surface texture or surface topography, is the nature of a surface as defined by the three characteristics of lay, surface roughness, and waviness.. It comprises the small, local deviations of a surface from the p ...

and relief of the artefact thus lit. It is widely used in the examination of works of art.

Examination of paintings

Using raking light, the effects of

impasto Impasto is a technique used in painting, where paint is laid on an area of the surface thickly, usually thick enough that the brush or painting-knife strokes are visible. Paint can also be mixed right on the canvas. When dry, impasto provides tex ...

and the surface texture of a

painting Painting is a Visual arts, visual art, which is characterized by the practice of applying paint, pigment, color or other medium to a solid surface (called "matrix" or "Support (art), support"). The medium is commonly applied to the base with ...

are accentuated by the increased illumination of surfaces facing the light source and the exaggeration of

shadows A shadow is a dark area on a surface where light from a light source is blocked by an object. In contrast, shade occupies the three-dimensional volume behind an object with light in front of it. The cross-section of a shadow is a two-dimensiona ...

on surfaces facing away from the light source. In some instances, raking light may help reveal

pentimenti In painting, a ; from the verb , meaning 'to repent'; plural ''pentimenti'') is "the presence or emergence of earlier images, forms, or strokes that have been changed and painted over". Sometimes the English form "pentiment" is used, especiall ...

(changes in an artist's intention). In the case of wall paintings, raking light helps show preparatory techniques such as incisions in the plaster support.

Conservation

Conservators In certain areas of England, conservators are statutory bodies which manage areas of countryside for the use of the public. Establishment, role and powers Conservators are bodies corporate generally established, and granted their powers, by a ...

examine objects under raking light during a

visual inspection Visual inspection is a common method of quality control, data acquisition, and data analysis. Visual Inspection, used in maintenance of facilities, mean inspection of equipment and structures using either or all of raw human senses such as vision, ...

and for

condition recording Condition or conditions may refer to: In philosophy and logic * Material conditional, a logical connective used to form "if...then..." statements * Necessary and sufficient condition, a statement which is true if and only if another given statem ...

. In the examination of easel paintings, raking light may help document

craquelure Craquelure (; ) is a fine pattern of dense cracking formed on the surface of materials. It can be a result of drying, shock, aging, intentional patterning, or a combination of all four. The term is most often used to refer to tempera or oil pain ...

, paint cupping, uneven tension in a

canvas Canvas is an extremely durable Plain weave, plain-woven Cloth, fabric used for making sails, tents, Tent#Marquees and larger tents, marquees, backpacks, Shelter (building), shelters, as a Support (art), support for oil painting and for other ite ...

, or

warp Warp, warped or warping may refer to: Arts and entertainment Books and comics * WaRP Graphics, an alternative comics publisher * ''Warp'' (First Comics), comic book series published by First Comics based on the play ''Warp!'' * Warp (comics), a D ...

in a

panel Panel may refer to: Arts and media Visual arts *Panel painting, in art, a painting on a wood panel (as opposed to canvas, a wall etc) *Panel (comics), a single image in a comic book, comic strip or cartoon; also, a comic strip containing one ...

. In the examination of wall paintings, raking light can help document surface deterioration phenomena such as the

efflorescence In chemistry, efflorescence (Derived from the Latin verb 'efflorescere' roughly meaning 'to flower') is the migration of a salt to the surface of a porous material, where it forms a coating. The essential process involves the dissolving of an i ...

salts In chemistry, a salt or ionic compound is a chemical compound consisting of an assembly of positively charged ions ( cations) and negatively charged ions (anions), which results in a compound with no net electric charge (electrically neutral). ...

and micro-

delamination Delamination is a mode of failure where a material fractures into layers. A variety of materials, including Lamination, laminate Composite material, composites and concrete, can fail by delamination. Processing can create layers in materials, suc ...

, and may be used for monitoring the effects of conservation interventions.

References

External links

*{{Commonscatinline, Raking light Imaging 3D imaging Painting Conservation and restoration of cultural heritage

Examination of paintings

Conservation

See also

References

External links