The sauceboat sat on a Formica counter in a kitchen in Rhinebeck, New York, last March. It was Georgian, London-marked, 1788, and it had been in the same family for six generations. The current keeper, a retired schoolteacher named Helena Vrooman, had been polishing it twice a year since 1972 with a pink wadding paste her mother swore by.
She wanted to know if she had been ruining it.
The honest answer is yes, a little, every time. The pink wadding contains a fine abrasive, usually a calcined alumina or a diatomaceous earth, suspended in a wax and solvent matrix. Each polish removes a microscopic layer of silver along with the tarnish. Over fifty years of twice-yearly cleanings, Helena had taken off perhaps two or three microns from the surface of her sauceboat — not enough to see, but enough to soften the original chasing on the rim, which once described a Greek key and now described a suggestion of one.
The professional conservator's first preference is not to clean silver at all unless the tarnish is actively damaging the object. A light, even patina of silver sulfide is in fact protective. It is when the tarnish becomes uneven, or when it begins to pit, that intervention is justified.
When intervention is justified, the method of choice is electrochemical reduction. It is older than most people assume. It was described in the late nineteenth century by chemists working at the South Kensington Museum, and it has been the preferred household method of conservators ever since.
The materials are unremarkable. A non-reactive vessel large enough to submerge the piece — a glass baking dish, a plastic tub, an enameled roasting pan. Aluminum foil, dull side up, lining the bottom. Hot water, near boiling. A handful of washing soda, which is sodium carbonate, sold in the laundry aisle. Common table salt is sometimes added; the literature is divided on whether it helps.
The chemistry is straightforward. The silver sulfide on the object's surface reacts with the aluminum in the foil, mediated by the alkaline electrolyte in the water. The sulfur transfers from the silver to the aluminum. The silver returns to elemental silver, on the object itself. No metal is removed.
What the method cannot do is remove dirt, wax, old polish residue, or organic film. For those, a gentle wash in lukewarm water with a small amount of pH-neutral conservation soap is the next step. Helena had a bottle of Orvus paste under her sink, sold for washing horses and quilts, which is also what the conservation labs use.
The sauceboat went into the foil-lined dish. Helena boiled a kettle. The washing soda dissolved with a faint hiss. Within thirty seconds the tarnish on the lower body began to lift, visibly, like a film of grey smoke detaching from the metal. Within four minutes the object was the colour of newly minted silver in some places, and a pale champagne in others. The chased Greek key returned to legibility.
There are caveats. The method should not be used on silver that has been deliberately oxidized for decorative contrast — niello, Victorian darkened backgrounds on repoussé, anything with intentional black lowlights. It will remove that intention along with the unwanted tarnish.
It should not be used on objects with applied or embedded materials that the bath might attack. Bone or ivory handles, sealed with shellac, may suffer. Tortoiseshell will not be happy. Velvet linings on a presentation case should obviously stay outside the dish.
It should not be used on silver-plated objects where the plating is thin or worn. The reduction reaction is fine for the silver itself, but if the underlying base metal is exposed at edges or high points, the alkaline bath can begin to attack the copper or nickel beneath. Pitting at exposed edges is a sign to stop.
And it should not be used on objects that have been gilt, parcel-gilt, or fire-gilded. The gold will not be harmed by the bath, but if there is silver tarnish under a damaged area of gilding, the reduction can leave a strange tide-line.
For a Georgian sterling sauceboat with no applied materials, no gilding, and no deliberate oxidation, the method is, by the standards of object conservation, almost embarrassingly safe.
After the bath, the sauceboat was rinsed in clean warm water and dried with two cotton dish towels, one to blot and one to finish. A conservator at the Winterthur Museum, where the senior metals conservator Anne-Marie Sandoval has spent her career on objects of this sort, recommends a brief final rinse in distilled water if the local supply is hard. The sauceboat had now been cleaned without losing a single atom of silver from its surface.
Helena asked, reasonably, what to do next. Twice a year was the answer. Not the polish — store the sauceboat properly. Acid-free tissue, a soft cotton bag, a closed cabinet away from rubber bands, wool felts that have not been treated for moths, and any open foodstuff that contains sulfur. Hard-boiled eggs, mustard, onions, and certain modern wall paints will tarnish silver from across a room.
Anti-tarnish strips, sold by archival suppliers and impregnated with activated carbon and a zinc oxide compound, can be tucked into the storage bag and replaced annually. A sealed display cabinet with a small dish of activated carbon at the back works on the same principle.
If the object is in daily use — a teapot, a christening cup, a child's first spoon — wash it by hand in warm soapy water immediately after each use, dry it at once with a soft cloth, and let the bright daily wear maintain itself without intervention. Silver in active use rarely needs the foil bath.
What it needs is to be used. Helena's sauceboat returned to her dining room sideboard the next morning, where it had stood since the late 1970s. She had been intending to bring it out at Easter, with gravy, for the first time in a decade.
The pink wadding went into the cupboard under the sink, where Helena said she would keep it for the brass doorknob on the bathroom. The brass doorknob, she added, had probably also been suffering.