Boys, glass tubes are made in the sizes shown in Fig. 2, and in larger sizes. You will use sizes 2, 4, and 6 in the following experiments.

Hold a piece of No. 2, with both hands, in the flame of the alcohol lamp, and turn it constantly (Fig. 3). Do you find that when the glass becomes nearly red hot, it becomes soft and bends easily?

Take the tube out of the flame, bend it into any shape you wish (Fig. 4), and allow it to cool. Do you find that the glass hardens when it cools and retains the bent shape?

Heat the tube near the first bend, turn it constantly, take it out of the flame, and make another bend.

Repeat this and make all kinds of fantastic shapes.

Place all hot glass on the cooling blocks, not on the table. Glass is used in many, many ways by the human race; for example, to make bottles, tumblers, window glass, and so on, and all of these uses depend upon the facts which you have just illustrated, namely, that glass becomes soft when heated and hard when cooled again.

Fig. 2. Sizes of glass tubing

Fig. 3. Heating Glass to soften it

Fig. 4. Bending glass