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Caring for... > Care and conservation of silver and plate
Care
and conservation of silver and plate
The word
“silver” often conjures thoughts of treasure and
very high-value objects. In fact, items made from this precious
metal are more common than you might imagine and most people
will own something made of silver: a small trophy, a coin,
a watch chain or a table ornament or implement. Silver has
an attractive colour and will take a high polish. It can be
worked in many ways: shaped by hammering or turning, or cast
into intricate shapes. It can be embellished by engraving,
inset with gems or plated with gold and it is often used in
association with polished hardwoods, ivory, or other metals
of contrasting colour.
The silver
used to manufacture most domestic-type objects originating
in the UK is sterling silver. This is an alloy consisting
of 92.5% silver and 7.5% copper. Many of the 'silver' objects
originating from the Middle or Far East and Central or South
America will have a very different composition, usually with
a much lower silver content in the alloy. In some cases there
is none at all - 'German Silver' is a white alloy made from
nickel, zinc and copper. This guidance applies to the care
and cleaning of objects which are in sound condition and made
only of silver, though the techniques described can often
be used when other materials are present.
- A specialist
metals conservator will have an understanding of the way
cleaning materials and methods can affect different materials.
They will advise if you are in any doubt about the composition
of an artefact or the best method for cleaning and repair.
What
can go wrong?
'Tarnish' appears as gradual discolouration and loss of polish,
the metal turning first to pink, darkening to brown, and then
to a very dark grey or black with a slight iridescent sheen. This is caused by sulphur compounds in the atmosphere, originating
from the burning of fossil fuels and other industrial activity.
Humans are also agents in producing tarnish – the salts
and greases in our skin are highly corrosive and can mark
a polished surface irreversibly.
Where
conditions have become more harsh, or an object has been severely
neglected, you may also see crusty, green-coloured deposits.
These are the corrosion products of the copper in the silver-alloy
as it corrodes. There are many causes for this, but common
ones are storage in damp conditions or the action of chemicals,
especially those from the residues of cleaning compounds.
- If
the green corrosion is extensive, then treatment by a specialist
conservator is advisable.
What
you can do - prevention
Avoid bringing silver into long-term contact with protein-based
materials such as wool, silk or leather when choosing materials
to store or display silver; these contain sulphur compounds.
You can use sulphur-absorbing materials in a case to
slow down tarnishing, e.g. Charcoal Cloth, Silver Safe,
or copper-impregnated plastic films.
Use clean cotton gloves to handle silver items –
especially when it is highly polished and at its most reactive.
Keep silver dust-free using a soft clean lint-free cloth
or a very soft hair brush. Dust can attract moisture and
initiate the tarnish or corrosion cycle.
Know your collection. Which items are valuable –
historically, personally, financially? You should not attempt
to remove even tarnish from these yourself if you value
them, but trust them to a specialist metals conservator.
Keep tarnish-removal for other “everyday”
items to a regular minimum. Bear in mind that each time
you do this you are removing a little of the original surface.
Keep the environment around your objects well-ventilated
and dry – dampness causes corrosion.
When moving an item, use two hands around the body of
a vessel and do not pick up by the handles, which are often
weakened with age and use.
Removing tarnish from silver yourself
If the tarnish is light then you may wish to remove it with a commercial
silver cleaning cloth. This will remove dust, light sticky
or greasy deposits and the dulling tarnish, leaving a brightly
polished finish. This works for large areas of plain, undecorated
silver, and its use can be a regular part of your general
housekeeping routine. Do bear in mind the points above about
not doing this too often and only for non-historical pieces;
remember to buy new cloths from time to time. Intricately
shaped or decorated surfaces will require the use of a liquid
cleaner.
If the
tarnish is heavy, then a liquid method such as a “silver
dip” might be effective. This works by chemically dissolving
the tarnish. It creates a very reactive surface however, which
will tarnish again quickly, so finish with a silver polishing
cloth. Follow instructions on the container carefully: wear
rubber gloves and, if you are using large quantities, goggles.
Use a fresh solution every time you clean the silver, rinse
and dry thoroughly using clean cotton cloths. Maintain the
finish with occasional wipe-over with a silver cleaning cloth.
Things
to avoid
Avoid wadding, creams and rouge sticks. These contain
abrasive compounds which, as well as polishing off the tarnish,
remove much more of the silver surface than the chemical
methods above. Over time and with repeated cleaning, this
will wear away the silver and any engraved decoration or
inscriptions. These cleaners often also leave crusty deposits
which harden and become impossible to remove.
Do not use brass or chrome cleaners on silver. They are
not designed for the purpose and contain much harsher chemicals
and abrasives needed for cleaning copper or brass.
Never use “electrochemical” cleaners. They
work by depositing a layer of another metal on top of the
original surface, permanently obscuring the original finish
and design.
A
note on lacquering
Most modern silver is protected after manufacture with a sprayed
lacquer finish. This is usually cellulose nitrate dissolved
in organic solvents. Commercial companies do offer a lacquering
service, but you should think carefully and take advice before
having this done to historic items, and consider the following points:
- A lacquered finish may look appropriate on modern articles
but does not suit more antique surfaces.
- Lacquer is very difficult to remove completely and safely
from a piece, particularly from decoration, inlays and intricate
areas; your objects may undergo a high degree of handling
and abrasion in the process.
- A lacquer finish protects the surface from handling marks
but is not a substitute for regular housekeeping and inspection
as a means of long-term preventive care.
- Small holes or scratches in the lacquer finish can cause
serious “spot” corrosion over short periods
of time.
Consulting
a conservator
Conservators specialising in metals have the practical
skills and technical knowledge to carry out cleaning, repair
and stabilisation of silver items of all periods. Their
approach will be based on safe practice and minimum intervention – preserving as much of the original item as possible
and retaining all related information and evidence.
- Conservation is a cost-effective option. A conservator
can survey and assess all the items in your collection and
go on to recommend and prioritise treatment and preventive
care regimes in line with your budget and needs.
- If you just require advice on lacquering, storage and
display materials, cleaning methods or sources for obtaining
materials - a conservator can help.
- Conservators can also arrange for items in your collection
to be analysed or sampled for purposes such as dating or
determining provenance.
Use the Conservation Register to Find
a conservator.
©
Icon, the Institute of Conservation 2006.
This article
offers general guidance and is not intended to be a substitute
for the professional advice of an accredited conservator.
The views expressed are those of the author or authors, and
do not necessarily represent the views of the Institute of
Conservation.
The Institute of Conservation would like to acknowledge use of the MGC publication 'Ours for Keeps' in the preparation of this text. The Institute of Conservation and its partners
accept no liability for any loss or damage which may arise
if this guidance is followed.
The Institute
of Conservation would like to acknowledge the support of The
Royal Commission for the Exhibition of 1851 in the production
of this guidance information. Further information on The Royal
Commission for the Exhibition of 1851 and its work is available
at www.royalcommission1851.org.uk. |
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