Visible light

Visible light is the only portion of the electromagnetic spectrum that is visible to the human eye. Visible light encompasses daylight, incandescent and fluorescent light sources. Examination with visible light is used in the initial stage of the examination of works of art. Such examination is frequently aided by the hand-held magnifiers and stereomicroscope, to zoom in on features of special interest. The direction in which the light falls on the painting can reveal the individual technical features as well as different conservation issues.

Observations with direct and diffused light can easily reveal discolourations, pigment changes and losses of the painting layer. 

When light source is located to one side of the object at low angle between 5º and 30º with respect to the examined surface, it is called raking or grazing light. This type of examination emphasizes the painting layer texture like brushstrokes, impastos, flaking paint and support deformations like bulges, creases and tears. The observation with raking light allows the conservator or art historian to study the artist’s technique and also indicates the areas that require a conservation attention. 

When light source is placed at the back of the painting and the front of the painting is examined, this is called transmitted light. This method produces information about the different fissures, cracks and thickness of the paint. This technique is also very helpful in examination of glass reverse paintings.

The results of the visible light examination can be recorded with standard photography techniques while photomacrography may be used to record information about the artist's materials, painting technique and document inscriptions.

Joseph Poulter Mackesy by Catterson Smith. XIX century. Ireland. Close-up of the face photographed in a diffused light. State before conservation. Joseph Poulter Mackesy by Catterson Smith. XIX century. Ireland. Close-up of the face photographed in a raking light. This technique emphasizes the relief of the painting and shows areas of lifting cracks in the paint. State before conservation.Joseph Poulter Mackesy by Catterson Smith. XIX century. Ireland. Close-up of the extensive tears and damages to the painting layer. The photograph was taken in a diffused light. State before conservation.Joseph Poulter Mackesy by Catterson Smith. XIX century. Ireland. Close-up of the extensive tears and damages to the painting layer. The raking light photography technique reveals the extent of the canvas deformations . State before conservation.Joseph Poulter Mackesy by Catterson Smith. XIX century. Ireland. Close-up of the hand photographed in a diffused light. State before conservation.Joseph Poulter Mackesy by Catterson Smith. XIX century. Ireland. Close-up of the hand photographed in a raking light. This technique enables to study the surface irregularities. State before conservation.Still life with yellow roses. Canvas oil painting. 1922. Ireland. Close-up of the painting photographed in a raking light. This technique gives a greater understanding of the relief of the painting (the shape of its surface) and how the artist has used the paint. State before conservation.Joseph Poulter Mackesy by Catterson Smith. XIX century. Ireland. Close-up of the corner of the painting photographed in a diffused light. The deformations of the canvas and painting layer are barely visible. State before conservation.Joseph Poulter Mackesy by Catterson Smith. XIX century. Ireland. Close-up of the corner of the painting photographed in a raking light. This technique gives a greater understanding of the deformations of the canvas and surface irregularities. State before conservation.