Kiln firing, its benefits and why you should kiln fire if you are selling your jewellery.
Once I have discussed the firing process with my students in class and we learn how to fire with a torch, the next question I am asked is; should I buy a kiln?
This is a question that always fills me with a certain amount of dread because what do I say? I realise kilns are an expensive asset for anyone to acquire and telling someone who has just gotten the silver clay bug that a kiln is required is like popping their delighted ‘ooh look what I made with this PMC and my own two hands’ bubble. So I tell them the truth….
Firing Silver Clay – the truth
The simple fact of the matter is that any silver clay item that you make will be a whole lot stronger if you fire it in a kiln. That’s because a kiln (well a kiln which is intended for small jewellery items that is) is specifically designed to maintain a controlled, consistent temperature over a prolonged period of time. Picture yourself standing with a torch over your carefully crafted item for a couple of hours and I am sure you can understand what I mean.
The reason this is so important is that the sintering process, which is the process where all the silver particles fuse together during firing of silver clay, takes time to complete properly. Hand firing and under firing both result in weak metal which will be porous and brittle and that can lead to jewellery that could easily be broken. I challenge you to try and break a piece of hand fired silver clay jewellery – pick a piece that you have resigned for the scrap pile and give it a go. I suspect that you will be able to break it without too much effort.
So what’s a budding silver clay artist to do? There’s a choice to be made obviously, fire by kiln or by torch. This choice will largely depend on what you intend to do with your pieces once you’ve made them. If you are keeping them just for yourself or giving them away to friends and family, then maybe investing in a kiln at this stage is not for you, however if you plan to sell them for good honest cash (is there any other kind?!) then I would strongly suggest that you do make an additional investment of some sort. Why? Because your customers deserve the very best quality product you can make and you don’t want their lovingly made piece of jewellery breaking after all that time and effort being invested in it.
If you can’t afford a kiln, then some places will offer a firing service for you – we do here at Bluebell Design Studio. We offer a flat fee service which means you can send us a kiln load (which is a lot of items) and we will fire, tumble and polish the pieces before sending them back.
Firing Silver Clay in the Kiln
The general rule of thumb is to fire a piece of silver clay for as long and as high as possible. The starting point is 900oC for 2 hours. If the temperature is any higher you are getting close to the melting point of fine silver. Any longer than 2 hours serves no purpose as by this time the maximum tensile strength of the clay has already been reached.
Of course there are constraints when using this method of firing; embeddable items such as sterling silver, glass and stones which cannot withstand the high 900oC temperature must be considered. That’s where you as the jewellery designer need to come up with a design which takes account of the use of the item you are making and the need for strength. Silver clay, once fired properly, can be treated like ‘normal’ silver in that it can be forged, shaped and soldered, so perhaps items can be added once your piece has been fired?
Silver clay is a fantastic medium, flexible and malleable it can be far easier to form pieces with it than from sheet silver but there are drawbacks and considerations which must be taken into account when designing your unique piece of jewellery. Things like what’s the purpose of the jewellery, how much wear and tear will it get, how is it likely to be worn. If you consider these things when designing and making your jewellery, that will guide you as to how your silver clay jewellery should be fired.
Part 3 – Hints and tips for easy and straightforward firing.