"If you want to be especially thorough, you should vacuum-pack the silver," says chemistry professor.
'Edna Falao is Europe's only female speedway rider. The young motor enthusiast has the same problem as all other prize-winning athletes: there is a lot of silver polishing,' the Norwegian news agency NTB writes about this picture, taken in 1954.(Photo: Aage Storløkken / Aktuell / NTB)
"When silver is exposed to air, a coating will form on the surface. The black coating is mostly silver sulphide – a compound of silver and sulphur," says Professor Einar Uggerud at the University of Oslo's Department of Chemistry.
Sulphur is present in the air and reacts with silver. Some foods therefore pose a greater problem than others.
"Eggs contain a lot of sulphur and are notorious for creating a coating on silver that you definitely don't want on the evening of December 24," he says.
That is why many of us turn to chemistry during the Advent season to remove this layer.
"I have only used ordinary silver polish at home," says chemist Einar Uggerud.(Photo: Amalie Huth Hovland / University of Oslo)
"Removes a little silver"
Annonse
Silver polish is designed to remove the sulphur layer, says Uggerud. Various substances can dissolve it, such as sodium thiosulphate – also called fixer. But silver polish is carefully formulated to be gentle on silver and safe for people.
"You could use sandpaper to make it shiny, but then you'd remove a lot of silver," says the chemist.
In principle, even chemical polishing removes some silver, says Uggerud.
"But we're only talking about a few layers of atoms, and there's plenty to spare. I don't think you'd notice the loss, even over a long period," he says.
There is, however, an alternative method that in theory does not remove silver at all.
Silver polishing at Gildevangen coffee house, probably in 1941 or 1942.(Photo: Langberg, Esther / Oslo Museum)
Can restore new, shiny silver
"We can use electrical voltage and reverse the polarity," says Uggerud.
Put more simply: Instead of removing something, you restore the silver on the spoon or candlestick.
"You can place the silver in the sink with aluminium foil at the bottom, fill with water, and add salt and baking powder," he says.
Uggerud adds a note of caution. The silver becomes shiny, but he does not know the long-term effect.
"I have only used ordinary silver polish at home. I wonder whether the silver surface could become uneven if you do this over and over again," he says, elaborating:
"Let's say you have a silver coin or an intricately carved object. It's possible that the details become blurred because the silver does not necessarily always settle where it originally was."
Over time, tiny microscopic bumps on the surface could make the object slightly less smooth and even, Uggerud says.
Can sand away damage – but it takes time
Annonse
If you are unlucky and have run your silver cutlery through the dishwasher and damaged it, the problem can be harder to fix. Knives are particularly vulnerable, says Uggerud.
"While the handle itself is made of silver, the blade is often made of steel, and the whole thing is held together with a cement and some glue. In the dishwasher, this binding material can seep out and end up on the silver," he says.
"I'm hesitant to recommend chemical methods when there's already a problem. You can always try sandpaper, but you have to be patient, and the result will probably not be what you want," Uggerud adds.
That is because you need to start with coarse sandpaper and then gradually move to finer grades. This allows you to remove both the residue and avoid scratches.
"Perhaps it's better to go to a silversmith and have it repaired," he suggests.
Tip: "Vacuum-pack the silver"
Christmas conservator Geir Thomas Risåsen puts his silverware in plastic bags to make silver polishing as easy as possible, he writes in his book God jul (Merry Christmas).
A clever trick, confirms Uggerud.
"It slows the process because less air reaches the silver. Many people think air consists only of nitrogen and oxygen, but it also contains particles and gases that cause oxidation," says Uggerud. " If you want to be especially thorough, you should vacuum-pack the silver. That would significantly slow down oxidation."
