51
B+WConservationist Susie Clark doing a
microscope examination of a Nicéphore
Niépce plate at the National Media Museum.© Dusan Stulik
a little research tells us that this process was
popular between 1839 and 1860, and the
support is a silver-plated sheet of copper,
giving the picture a distinctive mirror-like
surface. Further digging reveals that the
image is often placed behind glass, which is
sealed with paper tape, and the whole thing
is presented in a folding case covered with
leather, paper, cloth or mother-of-pearl. If
the glass becomes cracked, replacing it can
be risky as the surface of a daguerreotype
is so delicate that it has been likened to
the wings of a butterfly. Removing the
original tape can also reduce the value of
the item significantly. On the flip side,
leaving cracked glass in place can allow air
to reach the surface, eventually tarnishing
the image. In this instance, you need to call
a conservationist (see page 53). This type of
basic research can be carried out for your
entire collection. By working out which
materials and processes have been used, you
can deal with each piece sympathetically,
helping to ensure its preservation.W
hile some causes of
deterioration will be unique
to individual pieces, there
are a number of common
culprits. The first is careless handling.
Fingers, no matter how clean they appear,
can leave traces of oil, perspiration and dirt
on negatives and prints, causing harmful
chemical reactions. To prevent the emulsion
from becoming damaged, it’s important to
wear gloves when handling each piece. Many
people use 100% cotton gloves, without
complaint, but nitrile gloves (used by the
medical profession) are often preferable,as they don’t shed fibres. It’s best to handle
your collection as little as possible, and
to keep all of your items in their original
storage enclosures (see page 52). If you do
decide to take your pictures out of their
protective sleeves or mounts then make sure
that any surface you use is completely clean
and the room you view them in is free from
environmental pollutants such as cigarette
smoke, domestic detergents and cooking oils.
The next offender is excessive exposure
to light. Any print or negative left in direct
sunlight will sustain damage of some sort,
but serious signs of ultraviolet radiation
include discolouration of the support,fading, yellowing of the emulsion and
shifts in colour balance (where relevant).
In extreme cases, prints can also become
brittle. While direct sunlight is the most
destructive source, fluorescent and
tungsten lights also emit ultraviolet light,
so they don’t escape the blame entirely. To
minimise the impact, keep light levels to a
minimum and hang all your pictures away
from direct light sources of any kind.
Another cause of deterioration is extreme
heat. According to experts at the Northeast
Document Conservation Center ‘the rate of
chemical deterioration of most photographic
materials doubles (approximately) with everyUnknown photographer. Portrait of a woman, c.1950. Dye transfer print that would fit very
nicely into a collection.© National Media Museum/SSPL‘According to experts at the Northeast Document Conservation Center
“the rate of chemical deterioration of most photographic materials
doubles (approximately) with every 10ºF increase in temperature”.50-53_ON_COLLECTING_174 ER/MB.indd 5150-53_ON_COLLECTING_174 ER/MB.indd 51 28/01/2015 10:1628/01/2015 10:16