> I was shown the "flame the mouth of the tube" technique while in
> college. When in training, I noticed that no one did that. When I asked
> why, the techs looked at me like I was from Mars and said there was no
> reason for it and that it just ended up burning your hands, so I've
> never ever done it since college.
The difference between plugs and caps.
When taking out a plug, there is a good chance of contamination: the end of the
tube is not sterile.
With a cap that fits over the tube there is no such problem. Unless you touch the
rim of the tube with your fingers.