PMC (or Precious Metal Clay) can be fired using any type of furnace that is able to sustain the required temperature with reasonable stability. Nearly any type of kiln that has a pyrometer - similar to those which are used for burnout or enamelling - will also work for various PMC projects. A kiln should always be used in a location that is away from any type of combustible surfaces or objects, and it should also be plugged into the right type of plug socket, as well as being in an area where wiring will not be snagged or tripped over.
It is a good idea to have work gloves available when you are firing PMC materials, as well a pair of long-handled tongs. You should also put a heat resistant surface (such as a brick) somewhere near to the kiln that you can set your work on when it is ready to take out of the kiln.
There are programmable kilns available for use with PMC that maintain a selected temperature throughout the entire firing process. This can be a much safer option for those who work with PMC projects. These kilns shut off on their own when they are not in use and, whilst this type of kiln is not essential for creating superior PMC items, it is a great choice for those who wish to be cautious while creating PMC silver clay jewellery items and other creative objects.
The number one piece of advice to heed when using a kiln is to be careful. You will be working with extremely high temperatures, so you should be completely comfortable with every aspect of the process before you start.
An issue that some people have when working with PMC is shrinkage of the clay that they are using. Whenever PMC is fired, the water and the binder vaporise and disappear, which means that the clay will then decrease in size by about 30 per cent. The object that you are working with after firing is usually reduced in size by around 70%, overall. Therefore, the item that you create will be able to keep its form, but it will be quite a bit smaller. This can be very helpful when it comes to creating small jewellery pieces, but do keep the shrinkage in mind if you are hoping to create a larger item instead.
There are a few steps that you will need to take when it comes to firing your PMC material. First you will need to set the completed PMC object on a piece of heated tile while it is surrounded by alumina hydrate (if it is not a flat object). Then you will need to set the tile into the kiln on the bits of brick that help to lift it up off the floor. Either program the kiln or fire it up manually by turning it to a high setting. PMC does not need to be vented during the firing process. However, when other materials are included in the object (such as cores), venting will be necessary.
If you are using a manual machine, once the pyrometer shows that the correct temperature has been reached, you will need to turn the dial back slightly to ensure that the temperature does not go any higher. Maintain this temperature for at least two hours before you remove the PMC object.
PMC, a material that can be moulded into silver jewellery pieces, needs to be fired before it is wearable. This guide looks at the processes involved in firing Precious Metal Clay.