FIG. 84
WIRE FUSED INTO GLASS
It is difficult to make a secure joint between iron or copper wire and glass because they both expand and contract more than glass when heated and cooled. It is easy to make a secure joint between platinum wire and glass because platinum and glass expand and contract at practically the same rate when heated and cooled. Platinum, however, is too expensive to be used for ordinary experiments.
Experiment 65. To cut window glass.
The common glass cutter is a small very hard steel wheel mounted on a handle (Fig. 85). Practice with one on a pane of glass: place a ruler on the glass, draw the wheel along the ruler (Fig. 86) with sufficient pressure to scratch the glass, place the under side of the scratch exactly over the edge of the table, and press down on both sides.
FIG. 85
A GLASS CUTTER
Experiment 66. To bore a hole in glass.
FIG. 86
CUTTING A PANE OF GLASS