Melting glass tubes and rods. Insert the end of the cut tube or rod into the flame and slowly heat it up, constantly turning, until sharp edges are clearly rounded. Place a piece of rubber tube on the end of the rod, cleanly washed out, to prevent scratching the glassware while stirring.
Bending glass tubes. Warm the tube with both hands at the bending point, turning it over and over again. The tube should be heated a little longer than the required arc length. After the glass has softened, remove the tube from the flame and bend it, while slightly stretching it. Heating it too short and bending it with a small arch will lead to a collapse of the tube on the inside of the arch.