Raking light, the illumination of objects from a light source at an oblique angle or almost parallel

Parallel

-Mathematics and science:* Parallel , an imaginary east-west line circling a globe* Parallel circuits, as opposed to series* Parallel * Parallel evolution* Parallel transport* Parallel of declination, used in astronomy-Computing:...

 to the surface, provides information on the surface topography

Topography

Topography is the study of Earth's surface shape and features or those ofplanets, moons, and asteroids...

 and relief

Relief (disambiguation)

The word relief comes from the Latin verb levo, to raise, lift up, elevate, with the addition of the Latin inseparable preposition re-, which has three distinct meanings: back, against and again. The Latin composite verb relevo results....

 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

In English, the borrowed Italian word impasto most commonly refers to a technique used in painting, where paint is laid on an area of the surface very thickly, usually thickly enough that the brush or painting-knife strokes are visible. Paint can also be mixed right on the canvas...

 and the surface texture of a painting

Painting

Painting is the practice of applying paint, pigment, color or other medium to a surface . The application of the medium is commonly applied to the base with a brush but other objects can be used. In art, the term painting describes both the act and the result of the action. However, painting is...

 are accentuated by the increased illumination of surfaces facing the light source and the exaggeration of shadows on surfaces facing away from the light source. In some instances raking light may help reveal pentimenti or changes in an artist's intention. In the case of wall paintings, raking light helps show preparatory techniques such as incisions

Fresco

Fresco is any of several related mural painting types, executed on plaster on walls or ceilings. The word fresco comes from the Greek word affresca which derives from the Latin word for "fresh". Frescoes first developed in the ancient world and continued to be popular through the Renaissance...

 in the plaster support.

Conservation

Conservators examine objects under raking light during visual inspection and for condition recording. In the examination of easel paintings

Easel

An easel is an upright support used for displaying and/or fixing something resting upon it.-Etymology:The word is an old Germanic synonym for donkey...

, raking light may help document craquelure

Craquelure

In art, craquelure is the fine pattern of dense "cracking" formed on the surface of paintings, in particular due to the aging of paints. It is often used to determine the age of paintings and to detect art forgery, as craquelure is a hard-to-forge signature of authenticity.-Authentic:Authentic...

, paint cupping

Cupping

Cupping can refer to:* Coffee cupping* Fire cupping, and other alternative health cupping methods* "Cupping", a form of unusual tire wear due to bad wheel alignment...

, uneven tension in a canvas

Canvas

Canvas is an extremely heavy-duty plain-woven fabric used for making sails, tents, marquees, backpacks, and other items for which sturdiness is required. It is also popularly used by artists as a painting surface, typically stretched across a wooden frame...

, or warp

Wood warping

Wood warping is a deviation from flatness as a result of stresses and shrinkage from the uneven drying of lumber.The types of wood warping include:* bow : a warp along the length of the face of the wood...

 in a panel

Panel painting

A panel painting is a painting made on a flat panel made of wood, either a single piece, or a number of pieces joined together. Until canvas became the more popular support medium in the 16th century, it was the normal form of support for a painting not on a wall or vellum, which was used for...

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

Efflorescence

In chemistry, efflorescence is the loss of water of crystallization from a hydrated or solvated salt to the atmosphere on exposure to air.-Examples:...

 of salts and micro-delamination

Delamination

Delamination is a mode of failure for composite materials. Modes of failure are also known as 'failure mechanisms'. In laminated materials, repeated cyclic stresses, impact, and so on can cause layers to separate, forming a mica-like structure of separate layers, with significant loss of mechanical...

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

External links

• Image with slider showing the effect of raking light (Hamilton Kerr Institute
  Hamilton Kerr Institute
  The Hamilton Kerr Institute is a branch of the Fitzwilliam Museum in Cambridgeshire, England. It is also part of the University of Cambridge.- Facilities and logistics :...
  
  )