Conservators can look closely at works of art using an Ultra-violet lamp in a darkened room.
Rays from an ultra-violet lamp cause some paints and varnishes to fluoresce (turn bright white).
The substances that become fluorescent absorb the invisible U-V energy and re-emit it as visible light.
The painting glows in the dark.
This technique is useful to detect where the painting has been restored or re-touched.
Since the varnish, rather than the pigment, is usually the most fluorescent material, any paint on top of the varnish
Sometimes older retouchings, repairs and damages are covered by a further layer of fluorescing varnish and are more
difficult to see.
But even then they will be a little darker and with experience the conservator can usually get a good idea of the
condition of a painting.
Cross section of Ophelia under U-V light
© Tate Photography,
By looking at a small sample of paint from the edge of Ophelia under U-V, we can understand the method
by which the painting was made.
This 'cross-section' of paint has been removed from an area of the painting that would normally be under the frame.
The sample is viewed through a microscope so we can see the layers of paint and the thickness of the paint.
The sample tells us that there is a layer of lead white underneath a layer of zinc white.