a carbon rod
when makeing carbide you dont want to use powdered lime as it will blow out of the furnes, you need some thing thats denser. your charcoal also should not be too fine or it will be blown out too.
you will also need a steel crucible to melt the lime in. I have noticed that if a cast iron pot is used, it can crack and if that happened with a full pot full of molten carbide.... I think you should get the point. the size of your carbon rod should be a certain size so that it will work correctly (i'll talk aabit more about this later when it comes to runnig your furnes, just remmber the size of the rod determines the size of the furnes. AMPS to size of rod.)
I haven't finished this project but, i am working on it! if it interested you iam sorry its not finished yet. if you would like to know more just ask away iin the comment section below.