BookRix

Glass-blowing is neither very easy nor very difficult; there are
operations so easy that the youngest laboratory boy should be able to
repeat them successfully after once having been shown the way, there are
operations so difficult that years are needed to train eye and hand and
judgment to carry them out; but the greater number of scientific needs
lie between these two extremes. Yet a surprisingly large number of
scientific workers fail even to join a glass tube or make a T piece that
will not crack spontaneously, and the fault is rather one of
understanding than of lack of ability to carry out the necessary
manipulation.