Light:
Light is a hazard. Even small amounts of light can damage a poster
over time*. Be sure to use good quality light, and in as low of
intensity as possible. *Over time, meaning long tearm exposure!!
If all light is potentially damaging and the damage is
cumulative, any exposure is harmful, especially to a highly light
sensitive material like paper. Because works of art and cultural
artifacts are meant to be seen, however, guidelines for limiting
exposure are desirable. A limit of 50,000 lux hours has been suggested
for very light sensitive materials. Lux hours or lx.h are determined by
multiplying the level of light, numerically expressed in lux, by the
hours the object is exposed to that light (light can also be measured
in footcandles or lumens; one footcandle [lumen] equals approximately
11 lux). If an object is lit for 10 hours a day at 50 lux, the limit of
50,000 lx.h is reached in 100 days (50 lux x 10 hours x 100 days). At
100 lux the limit is reached in 50 days. The higher the light level the
shorter the exposure time. Some institutions have started to keep
exposure histories for their most valuable or light sensitive
materials. Rooms lit at 50 lux may seem very dim, especially to someone
who comes inside on a bright day. The eye does adjust, however, and
good lighting design helps a great deal. A sign explaining the reason
for the low levels usually mollifies the public.
Paper
Light can cause darkening of paper and fading. Damage by light goes
beyond visual alteration by attacking the physical structure of paper,
causing weakening and embrittlement. All light is damaging. The higher
the light levels, the greater the potential danger. Sources rich in
ultraviolet (UV) radiation are especially hazardous. Because light
damage is cumulative, even low levels can degrade paper if the exposure
is long enough. Conservators therefore recommend that no valuable
artifact be permanently displayed.
Even if ultraviolet filtering glazing is used, paper objects should be
hung in areas of subdued lighting. Because light at any level is
potentially damaging, conservators advise that no paper based work of
art be kept on permanent display. In addition, storage and display
areas should be cool and dry with minimal fluctuations of temperature
and relative humidity. Climatic fluctuations not only weaken paper over
time but can cause unsightly rippling or distortion of the sheet.
Proper framing will buffer a work of art against minor short-term
climate changes but will not protect against seasonal or long periods
of high humidity. As is the case with all works of art and historic
artifacts on paper, the environment surrounding framed objects is
crucial to their preservation.
Preventative Strategies
UV filters are available as plastic sheeting
or as rigid panels. The sheeting, usually acetate film, can be cut with
scissors and applied directly to windows or cases. Tinted UV films will
reduce the intensity of the light as well. Although film is less
expensive than rigid panels, it is less attractive and may be difficult
to remove later on. At present it is not known how long UV-filtering
films remain effective, although informal experiments suggest that they
have limited life. The only way to determine if the film is still
filtering is to measure the transmitted light with a UV meter.
UV-filtering panels can be used in windows, cases, or frames. They are
available in either glass or acrylic sheets. For several decades
museums have used an acrylic, UF-3 Plexiglas made by Rohm and Haas.
More recently other companies have introduced UV-filtering acrylics or
glass. When choosing such glazing, check the product information to
make certain the UV-filtering capacity is greater than 90%. Some
acrylics and most types of glass filter little or no UV. Ordinary
non-glare glass is not UV-filtering, although there are non-glare
products with this feature. Before using acrylic panels as window
glazing, check that local fire regulations are not being violated.
Filtering panels can also be used as secondary glazing on existing
windows. If mounted inside in a manner similar to interior storm
windows, filters give thermal control as well as UV filtration. If the
budget does not permit this type of installation, hanging the sheets
inside the windows from hooks is effective as long as the panels are
larger than the window glass so that all light from outside is
filtered. White paint containing titanium dioxide on the walls and
ceiling of a room will absorb a certain amount of ambient UV radiation.
However, other measures to control UV are still necessary.
Dario.
[EMAIL PROTECTED] wrote:
NOW, lets talk about this.....very interesting topic....I also
feel the same way...how can we really believe in that.....I do not let
any poster have any sun on the image of any art....so...can anyone else
tell us that UV plexiglass does protect the poster of UV light....DOES
ANYONE KNOW THAT ELECTRIC LIGHT BALLS ALSO has the same impact as UV or
sun light ????? After many year, maybe over 20 years I have never
received any answer.....what is really the impact of our framed posters
in house or from the "very sun".
Please let me know BECAUSE I am lost.....
Philipp
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