How to Make and Use Precipitated Calcium Carbonate Silver Polish

How to Make and Use Precipitated Calcium Carbonate Silver Polish

How to Make and Use a Precipitated Calcium
Carbonate Silver Polish This video demonstrates how to prepare and
use silver polish made with precipitated calcium carbonate. This polish is considered mild because it
does not remove too much of the silver under the tarnish. Using this silver polish avoids using commercial
polishes, which may contain unknown abrasives or additives that are harmful to the object. The
decisions to remove tarnish from silver, on how much tarnish to remove and on the final
appearance should be made jointly by a conservator and a curator. To get started, here is a list of equipment
and materials required to make and use the polish:
Tarnished silver, Disposable nitrile gloves,
Precipitated calcium carbonate, Water,
Petri dish to hold small quantities of the polish,
Spatula, Lint-free cotton pads for polishing,
Soft natural fibre brush, Plastic wrap,
Acrylic sheet such as Plexiglas, Mild detergent such as Orvus or Ivory dish
soap, Clean cotton flannel cloths for drying and
for removing residual abrasive powder To make a small amount of silver polish for
testing or for polishing a single object: Use a spatula to transfer some precipitated
calcium carbonate to a Petri dish. Add water and stir with the spatula to form
a cream-like paste. We recommend that you test a batch of precipitated
calcium carbonate that has not been used before. To do this,
Use a new piece of acrylic sheet and remove the protective plastic film. Cut small squares of a cotton pad. Wipe a small part of a cotton pad through
the carbonate paste. Rub the cotton and paste back and forth several
times over a distance of a few centimeters on the acrylic. Examine the acrylic for scratches. With clear acrylic, scratches are easier to
see if black cardboard is placed behind the acrylic sheet. Hold the acrylic at different angles to the
light to find the best angle to see the scratches. If there are scratches, label the calcium
carbonate as unsuitable for polishing silver and find a different source of calcium carbonate. We can now get started on polishing tarnished
silver. Here’s how to do that:
Prepare a suitable workspace, including a padded work surface. Put on a pair of disposable nitrile gloves
before handling silver or chemicals. Remove dust with a soft natural fibre brush. Brush lightly. Ensure the brush is clean, as dust particles
can scratch the silver. If the brush has a metal ferrule, cover the
ferrule with tape so the metal cannot scratch the silver. Use plastic wrap to cover any materials that
should not be exposed to water or solvents (bone, wood or ivory, for example). Do not allow water to get into hollow handles
or other hollow parts of an object. Clean the silver with a few drops of mild
detergent and water to remove any dirt and grease. Dry well. As was done in the test on acrylic, wipe a
cotton pad through the carbonate paste. Polish the silver surface with the cotton
pad by gently rubbing the surface. Use a circular motion where possible. Replace the cotton pad when it is soiled. Always use a clean pad to wipe through the
carbonate paste. Stop often to wipe off, rinse and inspect
the area being polished. Do not assume that the object needs more polishing
just because a clean pad turns dark with polishing. Even after all the tarnish has been removed,
the pad will still turn dark as the abrasive removes silver from the surface. Do not spend too much time polishing any one
area. It is better to go over the entire object
several times rather than polish one area too much at once. If one area is polished too much, the whole
object may have to be polished to the same level. Once polishing is done, rinse the surface
to remove fine particles of precipitated calcium carbonate. If possible, rinse under running water; otherwise
use wet cotton flannel or cotton swabs. Take care not to scratch the silver with
cotton swabs made with wooden applicator sticks as wood may scratch silver. Dry the object well with soft absorbent cloths. Make sure there is no water left in crevices. Don’t polish too much. This can remove the details from a silver
object, or the silver in a plated object, revealing the underlying metal. Shown here are examples of damage to silver-plated
objects caused by excessive polishing: Silver-plated copper tray where the reddish
colour of the underlying copper is visible. Silver-plated brass goblet where the golden
yellow colour typical of brass can be seen. Silver-plated lead candlestick where the dull
gray areas are lead. Silver-plated pot for tea or coffee made of
nickel silver, where some of the silver plating has worn off. Nickel silver is an alloy of mainly copper
with nickel and zinc but no silver.

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