Dutch gold ( Dutch leaf, Dutch metal )
The generic name for a blocking foil that has
found considerable use as a substitute for gold
leaf since the latter years of the 19th century.
It was introduced in Germany and its use, in sheet
form, expanded rapidly, followed by a similar foil
in roll form. Although often referred to as
"bronze leaf," bronze being an alloy of copper and
tin, it is actually composed of brass, which is an
alloy of copper and zinc. As the amount of copper
is increased, the color of the leaf deepens.
Unlike gold leaf, Dutch gold discolors, tarnishing
more rapidly in polluted environments. When
blocked on leather, the leaf or foil turns green
very quickly; and even when blocked on cloth or
paper, it will eventually discolor. Discoloration
is due to the action of gases in the atmosphere,
such as hydrogen sulfide (H 2 S), plus
heat and light. Great differences exist in the
rate of tarnishing among the various brass foils,
however; flat foil for some reason discolors less
rapidly than the rolled Dutch gold. This may be
due to the high melting-point waxes used on the
flat foil but not on the rolled, which coat the
metallic particles after they are deposited on the
material in the blocking process. This coating
apparently acts as a (partial) seal against the
deteriorative effect of the atmosphere. Because of
the chemical action of the plasticizers in
pyroxylin fabrics, the deterioration of the foil
is more rapid on these fabrics than on starch
filled fabrics. (233 , 236 , 264 , 356 )
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