Lighting

Holly Chase <hchase [at] byugate__byu__edu> writes

>... I have been trying to find specific answers
>to what is the proper amount of lighting for oil paintings and
>haven't been able to come up with anything specific.

The very quick, and perhaps slightly snide, answer is: it depends.
There are recommendations all over the map for light levels on oil
paintings, from 15 footcandles up to 60, or even higher!  To some
extent this reflects the variety of paintings being lit.  But one
should always remember that paintings can be surprisingly
light-sensitive. We treated an 18th century French painting a number
of years ago. What appeared to be blue drapery turned out, when we
viewed the edge that had been protected from light for the
painting's lifetime by the rabbet of the frame to have once been
purple drapery--the red lake pigment having faded completely.  Other
paintings may be comparatively light-fast.  Some contemporary
paintings are also very light sensitive, and when the support is
exposed, as it is in some color-field paintings, and older oil
sketches, this too may be a problem.

I would suggest that the museum engage the services of a conservator
familiar with these problems to advise on this, rather than just go
ahead and *do* lighting.  In addition, since Ms. Chase states that
the only lamps that will be used are incandescent and halogen, I do
suggest you save your money and not buy a UV meter. Since the
recommended high limit on UV (75 microwatts/lumen) is derived from
the level found in incandescent lamps, and when halogen lamps are
used with the required glass front filter they too have that level
or lower, there is no need to measure UV.  I assume that the museum
already has a good footcandle meter.

Lighting paintings so that they have the desired appearance is not
as easy at it seems.  Because most museums use track systems these
days, many assume that simply pointing a fixture at each painting
from above its center point is the way to go.  One common problem is
that if the tracks are too close to the walls, they will cast
shadows from the frames.  Using multiple fixtures, with appropriate
wattage lamps and light-reducing filters usually produces a far more
successful result.  One must take into account many variables,
including the reflectance of the painting, its color, intensity,
etc. and the relationship of these to the wall on which the painting
is hung, as well as how you want the gallery to look as a whole.
Also, the situation of the gallery within the museum is important.
Do visitors approach the gallery directly from a bright front door,
or through darker galleries where their eyes can accommodate to
lower light levels?  Do they see brighter galleries--perhaps with
daylight--through doorways?  Many of these variables will affect the
apparent brightness of the paintings to be lit.  In general,
lighting should be seen as part art and part science, with greater
attention and skill required than at first may seem necessary.

Paul Himmelstein


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                  Conservation DistList Instance 14:51
                  Distributed: Tuesday, April 3, 2001
                       Message Id: cdl-14-51-003
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