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This condition is caused by an
inherent fault in the chemical
composition of the original
glass formula. Exposure to high
levels of relative humidity
during storage or display
causes salts to hydrate and
leach out of the glass. Alkaline
droplets then form on the
surface and appear as if the
glass is crying or weeping.
Photographs on metal supports are subject to corrosion and degradation caused by oxidation of the metal. The surface of a daguerreotype is susceptible to tarnish. Tarnish on daguerreotypes is composed of silver sulphide, silver oxide and silver chloride. Tarnish may appear at the edge of the brass window mat opening or over the entire plate. It can be characterized by a series of interference colours and/or pale grey, blue, green, brown or black.
Minute organisms known as mould spiders grow and feed on
organic matter in high relative humidity, high temperature and
stagnant air. Mould can be identified by white or beige tendrils
with a well-defined elevated centre growing on the surface of
A missing fragment of the support or
emulsion layer on a photograph.
A split in a photograph support
or emulsion caused by it having
been pulled apart forcefully.
A line, groove or ridge made by folding or crushing where the
surface of a photograph remains unbroken. It can be caused
unintentionally when a substrate bends over itself.
A bend in a material that may result in a crack or break in the emulsion /
support, as one part of the emulsion or support is laid over itself.
The physical process of scraping, roughening
or wearing away an object's surface due to
repeated friction or contact with other
Physical damage which causes an
indentation. The term usually
implies that there has been some
loss to the support or emulsion layer
of a photograph.
Silver Mirroring is a bluish-metallic deposit or sheen
cause by a physical alteration of the colloidal surface
of a photographic emulsion. It can change in
reflective light and appear iridescent, even bronze in
colour if severe. Over time, air pollutants in the
presence of heat and moisture can create a sustained
migration of silver ions in all directions.
A mark left on the surface of a photograph
caused by the oil, dirt or salt from
perspiration found on a fingertip.
Wrinkling or puckering in a wave-like manner that occurs
when a photograph or a support dries unevenly or due to an
extreme change in relative humidity.
A change in colour of a
photographic emulsion or a
support, usually to a darker,
more yellow or brown
appearance. May be caused
by light damage or exposure
to acidic substances.
Physical damage caused by a sharp object, resulting in a loss
of the photographic emulsion and/or support.
A discolouration that is caused by chemical
or physical interaction between different