We had read that it is possible to oxidise the surface of sterling silver, silver plate and copper using just the magical sulfuric properties of a humble hard-boiled egg. This intrigued us, and it was clearly going to be a safe, chemical free way to give an aged look to metal.
For testing purposes we made a pair of silver-plated metal bead and fire-polished crystal glass earrings with silver-plated head pins, jump rings and fish hook fittings. Something simple, light and bright in the hope that the oxidising effect would be very obvious.
- A hard-boiled egg fresh and hot from the pan (or two if you are oxidising a lot of pieces or a large piece)
- A shallow plastic box with a lid, large enough for pieces of egg and the metal objects to sit in it without the egg getting on the jewellery. Alternatively you can suspend the jewellery items above the egg - i.e. hang earrings on a wire.
Clean your metal to remove any surface oils that may be lingering there. Oil will prevent the sulfur gas reaching and working with the metal. Any copper that you want to age will need to be unlacquered. The oxidised finish on copper will be a dark brown colouring, if you want an instant blue-green patina you have to achieve this by other means.
It is essential that the egg used is hot. The oxidisation process can be speeded up if the metal to be oxidised is also warm - but this is not essential. Either heat your metal in scalding tap water, or use a little of the water used to boil the egg. If your piece won't be happy in a hot bath, then leave this step out.
Put your metal items into the centre of the box, or suspend from thread / wire.
Take your piping hot egg and using a tea towel or similar to prevent egg burn cut the egg into four. Cut right through the shell, no messing. Pop the quarters into the box and slam on the lid.
If you have placed your item on the floor of the box, you may want to turn your piece over after 15 mins to ensure the reverse gets the same exposure. The amount of time that you leave the oxidisation process to go on for depends on the effect that you want to achieve. After 30 minutes you should be able to see a discernible difference. If you want a darker colouring you can reheat the egg in a microwave and give it another go.
If the egg does get on your metal, it will do no harm, just clean it off.
On the left are the silver earrings pre-treatment, and on the right post-treatment. We left the earrings for several hours - due to other activities and this was just an experiment - but you might prefer to keep an eye on the process so that you can halt it when the effect you want has been achieved. If you want a darker effect repeat the treatment. We found that some of the silver-plated parts oxidised to a greater extent than others - i.e. the fish hook earwires became darker than the metal beads. You might want to test your components first before committing yourself to oxidising a large piece of jewellery with lots of elements, in case you find the uneven distribution of oxidation to be a problem.
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