Switzerland (Guillaume worked at the International Bureau of Weights and Measures near Paris) · Invar announced 1896; Elinvar announced 1919–1920
Invar and Elinvar Alloys
VerifiedElinvar and its later refinements (Nivarox and similar proprietary alloys) underpin virtually all mass-produced mechanical balance springs made since the mid-twentieth century.
Guillaume discovered that certain nickel-steel alloys have a near-zero coefficient of thermal expansion (Invar) or a near-zero thermoelastic coefficient (Elinvar), the latter directly applicable to balance springs that barely change elastic modulus with temperature.
Elinvar balance springs greatly reduced the need for separate bimetallic compensation balances, simplifying and improving watch regulation; Guillaume received the 1920 Nobel Prize in Physics substantially for this work.
How to verify this yourself
Guillaume's original scientific papers were published through the Bureau International des Poids et Mesures and the Comptes Rendus of the French Academy of Sciences; corresponding patents, where filed, should be sought in the French and Swiss patent registers under Guillaume's name rather than assumed from secondary sources.
Manufacturers known to have used it
- Most Swiss manufacturers via licensed or derivative alloys (e.g. Nivarox)
- Hamilton (Elinvar Extra)
Related photographs
No confidently matched photograph of this subject has been found yet. These photographs show a closely related record, and are not examples of the type described on this page.
Sources & references
- Nobel Prize official biography of Charles Édouard Guillaume (nobelprize.org)
- Comptes Rendus de l'Académie des Sciences, Guillaume's published papers (existence noted)
Where sources disagree, the disagreement is stated rather than resolved silently.