>>68796No, you don't need the fiberglass insulation. That is more for lessening problems if you topple it. It'll take longer for the fuel to spill out with the fiberglass in it.
Mine never had fiberglass in them. The biggest thing is making sure the metal can is hot enough to cause the alcohol to quickly vapourize. That way the vapours ignite and burn with a nice blue flame. The pot/pan should be touching the blue flames too. It should resemble the flame of a gas stove burner top.
Here's one of mine I made and was playing with (old old reposted image). Notice how there's 2 places where the flame comes from. The center hole and the ring of holes around the edge. When it only burns from the center hole that means the metal isn't hot enough to vapourize the alcohol properly. After the flame starts to come from the holes on the sides it is ready to set a pot on the top. You can see the blue flames with the pot on the top in the middle images.
These things are super simple to make. So, if you mess up on your first try, redesign it, and keep trying.