watch-glass

watch-glass

A scientist places a watch-glass on the lab bench.

Definition
  1. Noun:
    • A transparent cover for a watch face: "watch-glass" refers to the protective covering, typically made of glass or crystal, that sits over the dial of a watch to shield it from dust, moisture, and damage.
    • A scientific instrument: In laboratory contexts, a "watch-glass" is a shallow, curved piece of glass used to hold solids for weighing, as a cover for beakers, or for evaporating small amounts of liquid.
Usage Examples

  • As a watch part:

    • He replaced the cracked watch-glass on his vintage timepiece. (The transparent cover over the watch face was broken and needed to be swapped out.)
    • The watch-glass fogged up after swimming, obscuring the hands. (The protective cover became misty, making it hard to read the time.)

  • As a laboratory tool:

    • The chemist placed the powder on a watch-glass to weigh it accurately. (A shallow glass dish was used to hold the substance for measurement.)
    • A watch-glass was used to cover the beaker and prevent contamination. (The curved glass served as a lid during the experiment.)
Advanced Usage

  • "watch-glass" in horology: The term is specific to the watchmaking industry, where the material may be mineral glass, sapphire crystal, or acrylic. A damaged watch-glass can be replaced by a professional.

    • The sapphire watch-glass is highly scratch-resistant. (The transparent cover made of synthetic sapphire is durable against abrasion.)

  • "watch-glass" in chemistry: The shape of a watch-glass is slightly concave, allowing it to hold small quantities of substances or to act as a cover that allows air circulation.

    • The watch-glass was used for evaporating a solvent from the solution. (The curved glass facilitated slow evaporation without splashing.)
Variants and Related Words
  • Watch crystal (n): an alternative term for the protective cover over a watch face.
    • The watch crystal was chipped after the drop. (The transparent cover was damaged.)
  • Watch face (n): the front part of a watch that displays the time, located beneath the watch-glass.
    • The watch face is protected by a sturdy watch-glass. (The dial is shielded by the cover.)
Synonyms
  • Crystal: a transparent material used for watch covers (often made of glass or synthetic stone).
  • Lens: sometimes used informally to refer to the watch-glass, though less precise.
Related Idioms