Optician Achim Leistner hand-polished the Avogadro Project's silicon spheres, using a tactile technique nicknamed 'atomic feeling'

metrologycraftsmanshiptactile-cognitionmeasurement-historyavogadro-constant

The final figuring of the near-perfect silicon spheres described at claim-avogadro-silicon-spheres-among-roundest-objects-ever-made was done by hand by Achim Leistner, a precision optician at Australia's CSIRO. The Powerhouse Museum's object record has him relying, on the sphere project, on "precision handcrafting, to ensure minimisation of any irregularities" and, beyond his instruments, on "his hands to feel for any imperfections in the surface of the spheres," and states that "Leistner's fabrication method has been found to be superior to any purely machine-based method."

Two things this note previously attributed to that record are not in it. The nickname "atomic feeling" is absent from the object record; its only traceable home is a Tier-4 Wikipedia article crediting a BBC Four documentary no vault note has read (claim-leistner-atomic-feeling-corroborated-beyond-powerhouse-museum). So is the biography — Zeiss in Jena, qualifying as a precision optical craftsman in 1953, emigrating to Australia in 1957 — which circulates in retellings but has no located source here. The nickname is kept in this note's title as the name the story travels under, not as a sourced fact.

The superiority claim — that unaided fingertips outperformed instrumented polishing at the nanometer scale where these spheres are figured — is surprising and load-bearing, yet rests on a single Tier-3 museum record; it is held at seedling and flagged pending Tier 1–2 corroboration, tracked at question-verify-leistner-atomic-feeling-superior-to-machines.

The episode is a bridge into the vault's tactile-cognition thread: touch standing in for, or exceeding, visual and instrumented precision. It rhymes across three centuries with Nicholas Saunderson's "palpable arithmetic" (claim-saunderson-palpable-arithmetic-tactile-calculating-device) and the broader pattern at claim-blind-mathematicians-independently-reinvented-private-notation — though those cases substitute touch for absent sight, while Leistner's hands reportedly beat available machines. Different constraint, same move: when the eye or the instrument hits a wall, the hand takes over.