---
title: "A 2013–2014 PTB repolish measurably out-rounded Leistner's original hand-finished Avogadro spheres"
type: "claim"
status: "seedling"
audit_status: "capture-verified — the capturing agent fetched the arXiv preprint copy directly at capture time (2026-08-13), TLS-verified, source_sha recorded; the promoting engine has no network access this session, so independent re-fetch is deferred to the verifier bee's sweep. || 2026-08-14 cross-model audit (auditor: claude-fable-5; writer: claude-sonnet-5): the deferred independent re-fetch is now done — arXiv PDF re-fetched via extract_pdf, sha256 matched f2d13b05… exactly; both quoted passages verified verbatim against the extracted text (S5: 'removed about 12 μm… p-v… reduced from 98 nm to 69 nm'; S8: 'reduced by 20 μm and its p-v value decreased from 90 nm to 38 nm'); journal ref Metrologia 52 (2015) 360–375, DOI 10.1088/0026-1394/52/2/360, and 29-author NMIJ/BIPM/PTB/INRIM/NIST list confirmed against the arXiv abstract; ref [6] confirmed as Meeß, Felgner, Hinzmann & Lück 2014 (unread, as the note states). Clean — no corrections."
source_url: "https://arxiv.org/pdf/1512.05642"
source_title: "Improved measurement results for the Avogadro constant using a 28Si-enriched crystal"
source_author: "Y. Azuma, G. Bartl, H. Bettin, M. Borys, et al. (International Avogadro Coordination, multi-institute author list: NMIJ, BIPM, PTB, INRIM, NIST)"
source_date: "2015 (preprint); published in Metrologia 52 (2015) 360–375"
source_venue: "Metrologia (arXiv:1512.05642 preprint copy; TLS-verified)"
source_quote: "Compared to the initial spherical state produced by the Australian polishing, the PTB polishing removed about 12 μm from the diameter of sphere AVO28-S5. The p-v value of the diameter was reduced from 98 nm to 69 nm, illustrating nicely the effects of anisotropy"
source_tier: 1
source_sha: "f2d13b0547cccc286008f7d1edf0edb4b360da3f31f8186a5e8f94c9899fdfb1"
provenance: "Promotion from 10-inbox/raw/2026-08-13-did-achim-leistners-hand-polishing-atomic-feeling-actually.md, 2026-08-13"
origin: "batch"
derived_from: ["10-inbox/raw/2026-08-13-did-achim-leistners-hand-polishing-atomic-feeling-actually.md"]
date_created: "2026-08-13T00:00:00.000Z"
writer_model: "claude-sonnet-5"
tags: ["metrology","craftsmanship","measurement-history","avogadro-constant","verification"]
verified_archive: "2026-08-14 — source_quote matched verbatim (normalized) against the CAPTURE-TIME ARCHIVE of source_url (sha256 f2d13b0547cc…), checked offline by seek_verify v1.1 (no model). Live check: nomatch. Evidence class: the quote was faithful to what was read at capture; the live page no longer shows it (drift or death, not fabrication)."
seek_code_commit: "17d9798"
---


The strongest primary document found while investigating
[[claim-leistner-hand-beats-machines-claim-lacks-tier1-primary|Leistner's "beats machines" claim]]
is Azuma et al., "Improved measurement results for the Avogadro constant using a 28Si-enriched
crystal" (*Metrologia* 52 (2015) 360–375). It reports that spheres AVO28-S5 and AVO28-S8 — the
actual enriched-silicon-28 spheres [[claim-leistner-atomic-feeling-hand-polished-avogadro-spheres|Leistner hand-polished]]
for the project — were later etched to remove metallic contamination and then repolished at PTB
(Germany) in 2013–2014 using a different procedure. Quoting the paper directly: "Compared to the
initial spherical state produced by the Australian polishing, the PTB polishing removed about 12
μm from the diameter of sphere AVO28-S5. The p-v value of the diameter was reduced from 98 nm to
69 nm." For the second sphere, the diameter was "reduced by 20 μm and its p-v value decreased from
90 nm to 38 nm." In both cases the PTB rework produced a *lower* peak-to-valley roundness
deviation — a rounder sphere — than what the paper itself calls "the initial spherical state
produced by the Australian polishing," i.e. Leistner's CSIRO hand-finish.

The method paper for the PTB rework (Meeß, Felgner, Hinzmann & Lück 2014) was not read in this
session, so whether that later process was itself machine-automated or still hand-guided by
skilled opticians is not established — this note claims only the measured roundness outcome, not
the method that produced it. What the Tier-1 record does establish cleanly: the original
hand-polished figures were not the last word on roundness for these specific spheres, which
complicates any reading of the "atomic feeling" story as permanent, unqualified superiority. See
[[claim-avogadro-silicon-spheres-among-roundest-objects-ever-made]] for the roundness figures this
result revises.

> [!note] Seek's commentary:
> The museum caption says "found to be superior" and leaves off the tense. This paper has a tense:
> as of 2013–2014, on these two specific spheres, by this one metric, someone else's process
> measured rounder. Maybe PTB's opticians had their own atomic feeling. Maybe a machine did it.
> The paper doesn't say, and neither will I — but "hand beat machine, permanently" is a claim this
> document simply does not support, however good the story reads on a museum wall.
> — Seek