Inspecting Art Using
UV Light
Prior restoration can easily be detected through the use of an
ultraviolet light. The slightest alteration will stand out with clarity.By Carol B. Carney
When restoring, framing, buying, selling or
appraising artwork, it is imperative that you know if the item has been previously
restored. With this information, a restorer can proceed with caution or choose to avoid
inpainted areas. It is important to examine all artwork for hidden or concealed damage
that you might be blamed for at a future date.
Dealers and appraisers will also benefit
from the knowledge of earlier restoration when determining the value of artwork. Prior
restoration can easily be detected through the use of an ultraviolet light. In a darkened
room, ultraviolet lamps reveal alterations such as overpainting, repairs and floating
signatures on artwork that is normally invisible in daylight. The slightest alteration
will stand out with clarity.
The long-wave ultraviolet light should be
in the 365 nanometer range. At this wavelength, many materials absorb invisible
ultraviolet energy and transform this energy to visible colored light, easily
distinguished by the human eye. It is not reflected, but emitted light. In some cases it
is absorbed without emission, making these areas appear quite dark in contrast to the
fluorescent areas.
Here are some ways in which ultraviolet
light can be used to identify repairs and alterations in various forms of artwork:
OIL PAINTINGS
I suggest you take the customer into a dark room and view their artwork under ultraviolet
light to see if any previous restoration has been done. Point out that dark blotches
indicate repairs, floating signatures, over-painting and over-cleaning. Bluish-white spots
indicate the presence of lining compound, dark bluish-violet indicates picture repair
putty and very small blue dots are dust. A chartreuse haze indicates old varnish, which is
what you hope to see because it shows that no recent restoration work has been done.
It is my belief that oil paints should be
used when inpainting an oil painting. However, you may find that previous restoration has
been done in a variety of mediums. Glazing with oil paint is the most transparent of all
inpainting, while acrylic is one of the most opaque. It is hard to tell the difference
between acrylic and oil without a chemical test, but both are clearly visible.
Watercolor/gouache can vary in color from
pale blue to dark purple, orange, etc. Be aware that there is a masking varnish that is
used to hide restoration. It has the ability to absorb the UV frequency, but the surface
has a greasy quality. The masking varnish is noticeable because the density of the color
and the overall perfect coating of the varnish layer.
PORCELAIN, CERAMICS & GLASS
Repairs and cracks in fine porcelain and ceramic art objects fluoresce bright white. Lead
glass, even with as little as 1% lead, fluoresces an ice-blue color, while flint glass
appears white. Uranium-colored glass fluoresces a very bright green or yellow.
Clear glass repairs are easily seen with
the naked eye but not so in colored glass. Beware of judging the age of glass by the
color; short-wave radiation turns some clear glass to amber or purple in a matter of weeks
rather than years if aged naturally by sunlight.
PAPER ART
Bright areas in paper art show new patches of paper. Tissue and silking repairs are also
clearly visible. Smudged areas indicate erasures and very faint writing indicates erased
signatures. New touch-up on watercolors and gouache has the same indications as on oil
paintings.
Old paper fluoresces faintly whitish,
yellowish or grayish, but modern paper glows bright bluish white. Mildew (foxing) appears
yellowish and makes water stains easy to recognize. Old vellum appears yellowish white or
ivory, but modern vellum appears bluish white.
TEXTILES
A person can match the thread colors of the original piece, but the dyes of the new
threads will fluoresce white under an ultraviolet light where the repairs have been made.
MARBLE, JADE, IVORY & CLOCKS
Fresh cut marble will appear as a strong purple, while old marble will be a mottled white.
Fresh carved jade will appear as an intense color and old jade will be mottled in color.
Newly carved ivory will appear purple, but old ivory will be a yellow tone. If an antique
clock has a bright white face under an ultra-violet light you will know the face is not
original to the case.
Carol B. Carney is president of
Gainsborough Products Co., which specializes in oil painting restoration supplies. Free
catalog available. Call 800-227-2186 or click on www.gainsboroughproducts.com.
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