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Silver has been used since ancient times in the fabrication of decorative and
functional objects because of its working properties and pleasing color and
shine.
Pure silver is too soft for normal use, and so it is combined or alloyed with
another
| This article has been reproduced with the kind permission
of
Bishop Museum in Hawai'i, US |
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metal for strength. Sterling silver, for example, is 92.5% silver and 7.5%
copper. German silver is alloyed with copper, zinc and nickel. Silver objects
are stamped with a hallmark, showing that the metal was assayed for its purity;
the hallmark identifies the maker as well. If the object is not sterling but
silverplate or electroplate, the hallmark will indicate so.
Silver plate is made from a base metal such as copper with a thin coating of
silver electrolytically deposited on it.
A more durable technique is employed for Sheffield plate, where thin sheets of
silver and copper are sandwiched together in a furnace. Like gold leaf, very
thin sheets of silver foil can be applied to a variety of surfaces to create a
decorative effect.
Aside from the fact that it is soft, and therefore scratches easily, silver is
durable, and the only problem generally associated with it is tarnish.
In the days when wealthy families could employ a platoon of help, the daily
upkeep of silver was not a drawback. Nowadays, it is more common for silver to
go a long time between cleanings, and the build-up of tarnish can be quite
extreme, making the cleaning process more intensive. Silver molecules will
combine with certain other elements for which it has an affinity to create a
corrosion product which we call tarnish.
It follows then that removing tarnish (usually by means of an abrasive polish)
means removing some of the silver itself. In fact, the effect of years of
cleaning can be seen on older pieces of silver, where engraved decorations have
become faint due to loss of the surface. Therefore, tarnish formation should be
prevented as much as possible to avoid this gradual loss of silver.
Sulfurs are the strongest tarnishing agents, as anyone who has eaten an egg with
a silver spoon or fork will know. But sulfurs are also present as pollutants in
the air from the burning of fossil fuels, and even generated in our homes from
such products as foam rubbers, carpet padding, paints, wool or felt.
Even normal handling of silver leaves oily salts from our fingers which then
develop into distinct corrosion patterns. If silver were not exposed to any of
these tarnishing agents we would not need to clean it. As it is, we can only
try to reduce the presence of these agents so that our silver will not combine
with them to form tarnish.
Storage and handling
Silver kept in a cabinet or cupboard which closes securely enough to prevent air
exchange is at least somewhat protected from air-borne sulfurs and chlorides.
If the cabinet is made of wood, the interior surfaces should be well sealed
(two coats of water-based polyurethane can act as a barrier against acids in
the wood).
Other objects stored with the silver should be compatible-- plastics and fabrics
may generate tarnishing agents, while china and glass are undoubtedly safe.
Chests for storing silver flatware are generally lined with a fabric known as
silvercloth which is impregnated with tiny silver particles which sacrificially
absorb sulfurs; this fabric is also available in pouches or zippered bags of
various sizes for the storage of individual pieces, and in lengths for lining
containers or entire display cabinets.
This fabric is recommended for preventing tarnish; however, the particles will
eventually accumulate so much sulfur that they will gradually become
ineffective, so be aware that silvercloth will not last indefinitely.
Storing silver in plastic bags and cardboard boxes and tissue paper, unless they
are archival quality products, will do more harm than good due to the
aggressive acids and gases released by poor quality papers and plastics. But,
silver wrapped in acid-free tissue and placed in silvercloth and/or a sealed
polyethylene plastic bag (e.g. Ziploc type) will be well protected.
In recent years anti-tarnishing products have been introduced which work by
scavenging sulfur and other pollutants from the air. They come in strips or
blocks which can be placed in a well-sealed cabinet or storage container; under
these conditions the manufacturer states that the strips are effective for
approximately six months.
Finally, avoid touching clean silver with your hands; use a dish cloth or tissue
as a buffer. In museums, cotton or latex gloves are always worn by staff
handling silver and other metals to prevent the transfer of body oils and
salts.
Cleaning and tarnish removal
Tarnish is first visible on silver as a yellowish cast which over time deepens
to brown and eventually becomes a very dark and iridescent purple/black.
Tarnish is quite easy to remove in its early stages and very difficult to
remove once it has reached the black stage; thus, frequent light cleanings are
safer for your silver and less time consuming for you than waiting until silver
is very tarnished before cleaning.
In fact, silver used and then gently washed and dried on a
daily basis may seldom require tarnish removal.
Commercial soaps which contain phosphate can leave a brown stain on silver, so
choose a mild, phosphate-free detergent. Do not immerse pieces with wooden and
ivory attachments such as handles or finials, as water will harm these
materials. Silverplate should not be immersed for any length of time, as the
base metal will corrode through the plating.
After washing, dry and buff silver with a soft, clean cloth. Be sure to clean
your silver in this way just before polishing, to remove any gritty or greasy
dust and dirt from the surface.
Don't use rubber gloves when you wash or polish silver-- they emit sulfurs!
Removal of tarnish generally involves the use of an abrasive and so it is
referred to as polishing. Since silver is softer than many other metals, it is
of utmost importance that the appropriate abrasive be used-- a product
formulated for cleaning copper or brass would be much too strong for silver,
and leave disfiguring scratches.
In museums, important collections of silver are cleaned of tarnish using a
slurry made of specific abrasives such as precipitated calcium carbonate
(chalk) and water, applied with cotton or soft cloths. This method is preferred
because chalk is a soft abrasive, and because it avoids the use of commercial
products which may contain unwanted ingredients. However, studies have been
done at the Canadian Conservation Institute to identify safe commercial
products for home use.
For silver which is only lightly tarnished, a polishing cloth is gentlest as it
does not contain a high concentration of abrasives. Once silver has been
cleaned of tarnish, a polishing cloth can be used on a regular basis to
maintain a shiny appearance.
Even the gentlest abrasive will scratch if it is applied with enough force; the
trick to using any of these products is to take it easy. One publication notes
that you should avoid using pastes which are old or dried out for the very good
reason that the concentration of abrasive will be much greater than is safe.
After cleaning, unsightly polish residue will be left on the surface unless the
object is carefully washed; a toothpick kept soft by soaking in water can be
used to dislodge residue from crevices.
Liquid silver dips are another option, and although the danger of scratching is
lessened since they do not contain abrasives, they do contain acids which make
etching and pitting a possibility. They must be used with great care. If an
object is left in the dip for too long it will be overcleaned, and eventually
pitted.
Also, chemicals which leak into hollow feet or handles can pose a problem as
they will continue to work inside the piece; furthermore, the acids are harmful
to wood and ivory attachments, as well as to some other metals. It's more
prudent to swab the solution onto the silver and rinse thoroughly than to
immerse the silver in the dip.
Dips may leave a yellow cast on the piece after cleaning; a silver polishing
cloth is sufficient to remove this. It is difficult to recommend a way to clean
or remove tarnish from silverplate where the plating is thinly applied.
Loss of silver will eventually expose the base metal below, which will appear as
dark and dull patches, and may become disfigured with corrosion. Probably a
silver polishing cloth or a quick swabbing with a dip are the safest choices
for silverplate.
Some silver objects have areas of gilding applied-- this thin layer of gold is
very vulnerable to abrasives, so avoid these areas altogether when you polish.
Heavy use of abrasives on sterling silver can also gradually reveal firescale
(copper oxide), which shows as black spots and is a by-product of the
fabrication process; do not mistake this for tarnish, or conclude that it
indicates your piece is plated. Firescale is inherent, and repeated attempts to
remove it will only make matters worse.
Whatever product you choose for your silver, don't make the mistake of trying to
remove all tarnish; in decorative areas it is meant to enhance texture and
relief, and contributes to the aesthetic appearance of the piece. Your silver
will continue to give you pleasure if you take the proper steps to maintain it
by preventing tarnish as much as possible, and using the appropriate polish
when tarnish removal is required.
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