bloom
1. A deposit of ellagic acid formed in and on
leathers tanned with vegetable tannins of the
pyrogallol class, probably as a result of the
action of enzymes native to the original source,
i.e., bark, acorns, etc. Although bloom affects
the physical properties of leather in that it
increases weight yield, firmness, and water
resistance, it is deposited in insoluble form and
is not chemically combined with the fibers of the
leather. Its presence at times gives an unsightly
appearance to the leather. 2. A misty surface
appearance in an illustration, caused by an excess
of acid or too much drier in the ink. 3. The
dulling film that sometimes appears on varnish and
glossy paint films, particularly in industrial
atmospheres. It usually consists of minute
crystals of ammonium sulfate produced by the
reaction between sulfur dioxide, ammonia, and
oxygen in condensed moisture on the film. Bloom
can appear on a freshly lacquered surface when
rapid evaporation of the solvents causes the
temperature of the surface to fall below the dew
point. Moisture is deposited on the film, causing
a limited precipitation of cellulose nitrate and
giving the film a permanent cloudy appearance. (175 , 195 , 306 , 363 )
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