Not difficult. I have a piece of 1 or 1 1/4" conduit (I did this 20 odd years ago and spread the tube so I don't recall) with ends welded on (remove the zinc first) I then put a couple of propane torches under it for heat. Its long enough for mainsprings. Hand it from a rod clamped in a vice.
Danger? Depends.
You must melt the solidified saltpeter from the SIDE initially to prevent gas build up and an explosion may occur. It produces oxygen as it melts and will put a bubble of gas in the melt if the top does not have an opening. So heat from the side until its melted there in the center and does not solidify when heat is moved to the bottom. I heat the center and center side until there are two unmelted sections at leach end then melt the ends.
Wear a face mask. DO NOT put ANY wet item or oily item in the melt. Parts need to be clean and completely dry.
If this stuff gets on your skin you lose that skin since its going to be in the 700 degree or higher range so wear appropriate clothing. I.E. coverup.
Saltpeter, loses volume do to the oxygen production and more needs to be added from time to time, before any heat is applied...
Dan
