Here are some Tips & Techniques how to Utilize Conical Rods. Any glass color that has conical rods in the batch is indicative that the glass color was handpulled and not machine made. The conical rods are the part of the glass pull that is closest to the punty, thus the strange shape.
The really tough part of using conical rods is heating the rod in the torch flame without it popping all over your work table. There are ways to mitigate this problem and I am going to explain a few of the ways that I do this.
If you are lucky enough to own a kiln, it is a great way to heat up the fat ends of the conical rods. If you are not annealing beads at the time, you can ramp the kiln up to 1000 degree Fahrenheit, to give the conical rods a bit more heat which makes them easier to stick directly into the torch flame. Glass is a poor conductor of heat, so the end of the conical rod hanging out of the kiln door should be cool enough to hold on to if the rod is at least 10 inches long.
You can heat conical rods in the kiln at the temperature you normally anneal at, but the roughly 50 degree difference between 950 and 1000 degree can keep the conical rod from cooling down while you are moving it from kiln to the flame.
There is another way to heat the conical rods that doesn’t require a kiln. I have been heating the tips of my rods on a hot plate for years and it works for conical rods also. You need to get a flat piece of sheet metal about ¼ inch thick and big enough to fit over the elements of the hot plate. Never stick your rods directly on the hot plate elements. The metal plate you get can be steel, aluminum, or brass, depending on what is available.
If you are concerned about trapping more of the heat from the hot plate into the conical rods, get some thick fiber blanket (some people use the fiber blanket to cool their small beads in) and place it over the tips of the rods sitting on the heated metal plate. This method is very effective and inexpensive.
As I mentioned early, I have been pre-heating the tips of my glass rods for years because it cuts down on the shocky behavior of temperamental glass rod colors and it speeds up the whole beadmaking process.