| Watercolours should
ideally be kept in the dark to avoid the initiation
of harmful photochemical reactions, however, even
if stored in darkness changes can occur such as
yellowing of the paper, caused by air pollutants
e.g. sulphur dioxide.
Another discolouration reaction is that of 'foxing'
which has no precise definition, only the broad
idea of localised brown staining in the paper. There
are two schools of thought as to how these spots
occur, one- that they are caused by minute iron
particles in the paper, two- that the staining is
due to fungal attack. Foxing problems can be accelerated
by high relative humidity.
Other staining includes marks left by wooden backing
or stretchers being in contact with the paper support
leaving an exact replica of a knot or crack which
will leave 'air burns' in the paper surface. On
removing the mount from many watercolours the hidden
edge will reveal by comparison how the visible pigments
have been adversely affected by UV light. No treatment
can return colour- once faded, it is lost.
So besides correct conservation practice in the
framing of pictures and prints attention must be
paid to the correct storage and hanging of your
precious items- i.e. .no direct sunlight or placing over radiators
and fires- thus minimising changes in relative humidity.
BEFORE RESTORATION
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AFTER RESTORATION
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