Sterling silver is a fairly soft metal. If you need a harder metal, however, there are some things you can do. Jewellery makers, crafters, and metal workers have two ways to harden sterling silver at home: work hardening, and heat hardening. Depending on the type of sterling silver and size, one method usually works better than the other.
Grab your hammer. The quickest, and sometimes easiest way to harden sterling silver is by work hardening it. This means that the more you work with it and manipulate the metal, the harder it gets. This works best with sterling silver wire for jewellery because it manipulates easier than thick chunks. Beat it with a hammer, bend it, twist it, or stretch it, says the website Cool Tools.
Heat your oven to 316 degrees Celsius if you don't want to twist or manipulate your sterling silver. This works for rings, or larger pieces that simply don't bend that easily. If your oven doesn't go up to 315 degrees C, heat it as high as it will go.
Place the sterling silver in the oven for one hour. Then remove with an oven mit or potholders and let it air-cool completely. If the silver encases a valuable stone, make sure that stone can withstand the heat. If it went through a kiln previously, it will withstand the heat of your oven without any problems.
Polish or finish your silver jewellery after the sterling silver cools completely.
Fine silver will not heat-harden, so don't try it.