Butt seal - Part 3

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In a continuous motion, take the glass out of the flame and then touch the ends lightly together and then slightly pull them apart. Notice that when you push them together, they will stick, but this union has a very sharp cleavage region at the point of contact. These sharp areas are bad because they can easily be broken once cooled. Also, because glass is a poor conductor of heat, it will be more difficult for the flame to heat the excess thickness of glass on the inside of the tube while you continue on to the next step which is to remove these folds, or sharp edges.