You might notice this post is a slight detour on my (mainly food oriented) blogging road. As you read below, you will find that it does contains a recipe, but one of a very different kind. No, not an entomological recipe as the title might suggest, but an electrochemical one.
It all began when I uncovered a set of beautifully etched silver plate fish knives and forks with bone handles from one of the chests in the dining room. The knives and forks bore the hallmarks H B & H ★ from the Sheffield firm of Harrison Brothers & Hawson, active from 1862 to about 1950. I haven’t been able to date them more precisely, but museum authorities in Sheffield think that the elaborate etched design might date to the earliest years of the 20th century.
Not having been used in many, many years, hidden away and stored in a plastic bag, they were in need of some TLC. A dull tarnish covered the silver plate and the bone handles were dirty and requiring a bit of attention.
Silver plate Restoration
The recipe came curtesy of my chemist son. The quantities can easily be doubled for a larger container.
- A sheet of aluminium foil
- 55g baking soda
- a pinch of salt
- 1 litre of hot water
Place the foil sheet in the bottom of a deep non-reactive bowl that will hold about 1.5 litres. Place the cutlery in the bowl, making sure the metal makes contact with the foil. Add the baking soda and salt. Pour in the hot water.
An electrochemical reaction is caused when the baking soda breaks down the surface layer on the aluminium foil and frees the aluminium ions. The salt, apparently acts as a quick vehicle for transporting the ions to cause the reaction that converts the silver sulphide (the tarnish) back into silver. On the other side of the equation, the aluminium ions change to aluminium sulfide which shows up as dirty yellow specks in the water. The water will bubble, giving off a slight smell of rotten eggs.
The process works quite quickly. A ‘tide line’ shows with a few seconds where the blade was submerged. The area near the handle needed to be hand polished to protect the bone. Some web sites that describe the process will tell you to wrap the handle in cling film, another way to protect it.
Several ‘baths’ might be needed to restore the silver plate to its once shiny surface.
Bone handles can be restored by first cleaning off any dirt, then dipping or coating them with oil (preferably mineral oil, but olive oil will suffice). Let the oil sit for a while – overnight if possible. Wipe the oil off and polish.
Now to find an excuse to use them!
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The electrochemical process is explained in full (chemical) detail on the interesting blog, Compound Interest.