Clockmakers have long pioneered the design and experimentation of new materials, often in response to demands from the state as well as the market. Late eighteenth and early nineteenth century research into the errors to which marine chronometers were liable is a superb example of this. Balance springs made of hard-drawn gold, resistant to oxidation, were used by John Arnold from the late 1770s, and subsequently by his son John Roger, until Arnold senior’s death. In 1828, Johann Gottlieb Ulrich patented a non-ferrous balance, while, in Glasgow that same year, James Scrymgeour produced a flat spiral made entirely of glass. It is the remarkable application of glass to the construction of balance springs that is the concern of this article. Specifically, the efforts of the firm of Arnold & Dent, and later Dent alone, to secure the performance of their marine chronometers against variations in homogeneity, magnetism, temperature and elasticity, by using new materials for their balance springs.