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Microfade testing measures the accelerated fading of photographs and related materials. It is a highly precise and minimally destructive technique used mainly to identify colourants and materials that have a high sensitivity to light.
Raking light is a light source that is positioned
on one side of the photograph so that the
light falls or rakes across the surface. This
lighting technique accentuates textures and
planar deformations of the photograph.
Here you can see that a cat has walked
across the surface of this photograph, leaving
its paw prints on the emulsion.
Fluorescence is the emission of light by a
substance that has absorbed light during
an exposure of radiation of a different
wavelength, such as an ultraviolet light or
black light. In conservation examinations
it is often used to identify coatings,
optical brightening agents, tarnish on
daguerreotypes, re-touching materials,
mould, foxing, tape and adhesive stains,
protein glues and oils, varnishes and
certain pigments and dyes.
Transmitted light is a light source that is
positioned beneath or behind the support so
that the light shines through the fibre matrix
and media, watermarks, chain lines, etc.
Testing different types of plastic is essential to determine if the plastic
is harmful for the photograph. This is the Beilstein test method.
When heating a copper wire, melt the plastic in question onto the
copper wire. Then place the copper wire with the melted plastic into
a flame. If the flame burns blue, the plastic contains bromide and is
therefore safe for photographs. If the flame burns green, the plastic
contains chlorine and should not be in contact with photographs.
Visual inspection under binocular microscope
A visual examination under a binocular
microscope provides a more accurate
means of examining photographic
materials than is possible with the
unaided eye. In some cases this
technique is essential for identification
purposes and can aid in the