Whether you have been using it in your microwave kiln, or your “proper” kiln, you may be be wondering what “high temperature wire” actually is. You may also be rather baffled and somewhat irritated by the high price you have to pay for what amounts to small quantities of this mysterious magical wire.
In this blog I will summarise what I have learned over recent months about “high temp wire”. My motivation is to address some of the well-intentioned mis-information you will find on the Internet. It is also to demystify the subject sufficiently so that you can purchase your high temperature wire with confidence and at a sensible price.
To begin with I refer you to the picture in which I simultaneously show you what I used to use and what I am currently using. I will explain what they are and how they differ without getting too technical.
At the bottom of the picture you will see a tiny reel of a high temperature wire from HotLine. It is costly and there’s not much of it. This seems to be the same situation with other brands of high temperature wire. After much meandering around the Internet I have come to a conclusion that Hotline’s high temperature wire is most probably Kanthal wire. Kanthal is a trade name for a metal alloy that contains iron, chromium and aluminium and, no surprises, comes from a company (with a good reputation) called Kanthal. This alloy will easily withstand kiln temperatures to more than 1300 degrees Celsius and it is routinely more expensive than the other samples I have shown in the picture.
At the top of the picture you will see three larger reels of a high temperature wire that I purchased from a specialist wire company (www.wires.co.uk in case you are interested). These wires were less costly, partly because they are made of an alloy called nichrome and partly because I bought them in bigger reels. Nichrome wire is not a trade name but the name hints at the dominant component metals – nickel and chromium. This alloy will withstand kiln temperatures up to around 1150 degrees Celsius – not quite so hot as Kanthal wires but still more than is needed for use in a glass kiln.
You may also come across Chromel and Nikrothal as kinds of high temperature wire. So far as I can tell they are just trade names for nichrome wire.
Incidentally, Kanthal and nichrome wires are used for kiln heating elements and I know potters sometimes use nichrome wire. Reassurance that they are both suitable for use in a hot kiln!
The difference between Kanthal and nichrome wires is not only their melting point. Their surfaces also “deteriorate” by oxidation in the hot atmosphere of a kiln in different ways. In practical terms I have noticed that Kanthal wire behaves more kindly in that it only dulls on firing, tending towards black. However, although nichrome wire also dulls, tending towards black, I have also noticed that sometimes I see small amounts of a greenish haze deposited on fibre papers (when I’m using a small piece of 3mm fibre paper to prop up hanger loops).
I have not noticed any other differences between Kanthal and nichrome wire, such as strength or resilience but do notice that one contains nickel whilst the other does not – something to think about when making jewellery that may be in contact with the skin of someone unfortunate enough to have a nickel allergy.
So, Kanthal is able to withstand higher temperatures and behaves better. But is the extra cost worthwhile? Should you instead purchase larger amounts of nichrome wire at a very much reduced price instead? This is a matter for you to decide.
I found it easier to purchase nichrome wires in the gauges I wanted and in lengths that were not ridiculously expensive. But I did not find anyone in the UK selling similar gauged wires in bulk lengths for Kanthal. So, my obvious choice was nichrome wire and I do not regret the decision – paying tens of pennies per metre (depending on the gauge) rather than pounds per metre is an easy decision when the outcome in terms of what I make is of no significant difference.
Oh, and a final note – you probably used nichrome wire when you were at school doing chemistry or microbiology. If you’re a high school teacher you might want to have a quiet word with the science technician and “borrow” some nichrome wire to experiment with.