is the art of applying metal-leaf
to a surface.
Techniques were developed
thousands of years ago to gild wood, metals and
other materials. Because of the
comparative thickness of the
gold leaf used in ancient
gilding, the traces that remain
are still remarkably brilliant.
All through history gilding has occupied an important place in
the ornamental arts of countries
around the world; and the techniques practiced today may be taken as typical of
the arts as practised from the
that are made into leaf
need to be highly malleable. They can be
pounded into sheets well below a
micrometre in thickness without
breaking or tearing. Today, the typical
thickness of gold leaf is about
100 nanometres or 0.0001 mm.
When made by hand, small pieces
of annealed metal are placed
between sheets of parchment and
pounded repeatedly with wooden
mallets. As the metal thins out,
it forms large sheets. These
sheets are divided and the
process repeated. The final
sheets of metal are trimmed, cut
to various sizes, and sandwiched
between sheets of paper to
At a thickness of
100 nm one square metre of gold
leaf corresponds to 0.1 cubic
centimetre or less than 2 grams
of gold would
cover at least 14 square metres.
is a very traditional process.
After the substrate surface is prepared by
cleaning, sanding, sealing,
priming, and coating with an
impervious lacquer or enamel,
the ground is ready for a "size"
of linseed and other oils
similar to varnish to be applied.
The size cures until it comes to
tack (that is, it has dried
enough to hold the leaf on to
the surface but is still "tacky"
enough for the leaf to adhere to
it). This can vary between a 3,
12 or 24 hour size. The larger
the area being gilded, the
longer “open time” needed to
complete the transfer of gold.
The leaf is cut to the
appropriate size with a gilder’s
knife on a pad of calf’s leather
and transferred with a tip (a
very soft squirrel hair brush)
and static electricity (which
picks up the gold). The surface
is then skewed with soft brushes
(a gilder’s mop of squirrel
hair), cotton wool or sable hair
to fully press the leaf against
the size and also remove any
loose fragments of leaf. Oil
gilded surfaces are not
burnished any further but a
final polishing removes all
traces of gold dust fully
revealing the beauty and lustre.
Any draughts or movement of air
including heavy breathing and
the gold leaf is likely to fly
off the pad! Outdoor projects
such as the domes of buildings
and large statues require a
temporary structure around them
to eliminate any wind as well as
control the temperature and
is available from specialist art
suppliers in booklets of 25
leaves, 80 or 85 mm square, and
either loose or attached to a
backing paper for easy transfer.
While pure gold is
yellow in color, gold can also appear to have other colors.
These colors are obtained by alloying gold
with other elements in
For example, alloys which are mixed 14 parts gold to 10 parts alloy
create 14 karat gold,
18 parts gold to 6 parts alloy creates 18 karat, and so on. This
is often expressed as the result of the ratio, ie: 14/24 equals
0.585 (rounded off), and 18/24 is 0.750. There are hundreds of
possible alloys and mixtures, but in general the addition of
silver will color gold green, and the addition of copper will
color it red. A mix of around 50/50 copper and silver gives the
range of yellow gold alloys the public is accustomed to seeing
in the marketplace.
Different colors of Ag-Au-Cu alloys
White gold is
an alloy of gold and
at least one white
metal, usually nickel or palladium.
Like yellow gold, the purity of white gold is given in karats.
Rose, red, and pink gold
Rose gold is
a gold and copper alloy
widely used for specialized jewellery due
to its reddish color. It is also known as pink
gold and Crown Gold. Although the names are often used interchangeably, the difference
between red, rose,
and pink gold
is the copper content–the higher the copper content, the
stronger the red coloration, as pure gold is yellow and pure
copper is reddish. A common alloy for rose gold is 75% gold and
25% copper by mass (18 karat).
Since rose gold is an alloy,
there is therefore no such thing as "pure rose gold". The highest
karat version of rose gold is also known as crown
gold, which is 23 karat.
Green gold alloys
are made by leaving the copper out of the alloy mixture, and
just using gold and silver. It actually appears as a greenish
yellow, rather than as green. Eighteen karat green gold would
therefore contain a mix of gold 75% and silver 25%.
Grey or moon gold
Grey gold alloys
are made by adding silver, manganese, copper or palladium in specific
ratios to the gold.
Purple and blue golds
Purple gold (also
called amethyst or violet gold) is an alloy of gold and aluminium.
Gold content is around 79% and can therefore be referred to as
18 karat gold. Blue
gold is similarly
an alloy, this time between gold and indium.
However, both are highly brittle as these alloys and therefore
cannot be manufactured into goldleaf.