How to Make a Test Tube #6

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As the glass becomes thinner and thinner, lower the glass into the flame so that you are heating a smaller circumference of the tube--aim the flame at the (thinning) bottom of the glass, not the tail, nor the wall of the tube. The important (and tricky) thing at this point is to maintain a tension on the glass as you pull the glass away. It should be just enough to let the glass get stretched thinner and thinner, AND not so little as to let the glass become overheated (and too soft) as to let the tail get cut off too early.

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