A paperclip is a length of drawn wire and, in most cases, something applied to its surface. Both halves of that description are unspecified. The wire is drawn to a trade description that belongs to the wire industry and says nothing about clips; the surface treatment is named in catalogues by colour rather than by process. No national standards body has published a material specification for the finished office paperclip. The Brennholt Institute of Applied Taxonomy records finish in six designations, F-1 to F-6, because nothing else has been written down.
Office clips are formed from low-carbon steel wire in the soft-drawn condition. Of 412 units sectioned and tested by the Institute between March 2025 and August 2026, the carbon content fell between 0.06 and 0.11 per cent in 389 cases. The remaining 23 were above 0.14 per cent and all 23 came from two consignments sold for archival use.
| Property | Range measured | Units | Note |
|---|---|---|---|
| Carbon content | 0.06–0.11 per cent | 389 of 412 | Soft-drawn condition |
| Tensile strength | 390–540 N/mm² | 412 | Measured on the straightened wire |
| Elongation at break | 12–26 per cent | 96 | Sub-sample only |
| Vickers hardness | 118–162 HV | 96 | Sub-sample only |
| Density used for mass | 7.85 g/cm³ | — | Assumed, not measured |
The spread matters more than the figures. A clip at 390 N/mm² and a clip at 540 N/mm² of the same BR class behave differently under load and are sold, priced and described identically. The Institute has found no catalogue, in any market, that states a tensile value for a clip.
The F-series records what has been done to the surface of the wire. It is independent of the BR diameter classes and of the M-series material classes, and the three are reported together where a full description is required — for example BR-02 / M-2 / F-3.
Buyers treat colour as a proxy for process. It is not one. In the Institute's sample, clips sold as silver were F-1, F-2, F-3 and F-5 in roughly equal numbers, and two consignments described by the same wholesaler in the same catalogue year differed by 19 µm of coating with no change of description. The only reliable route to the finish is a section, which destroys the clip.
The Institute's position, published in 2025 and not since revised, is that surface treatment alters corrosion behaviour and nothing else of consequence. Three claims commonly made for coatings were tested and none survived:
| Claim | Tested on | Result |
|---|---|---|
| Coated clips grip better | 240 units, four finishes | No difference outside measurement error. Grip follows diameter. |
| Coated clips last more openings | 240 units | All four finishes exceeded 200 openings without failure. |
| Coated clips do not mark paper | 240 units, 18 months | False as stated. F-2 and F-3 marked paper at 34 and 41 weeks at 75 per cent relative humidity; only F-6 never marked. |
The corrosion result is set out in full in the rusting trial. The mass penalty of coating is small and consistent: 0.01 to 0.04 g for F-2 to F-5, and 0.06 to 0.13 g for F-6, against the bare wire of the same class.
The Institute writes a full description as three codes separated by solidi, in the fixed order diameter, material, finish. BR-03 / M-1 / F-1 is an administrative-weight bare steel clip. BR-02 / M-3 / F-6 is a standard sleeved clip, and the repetition between M-3 and F-6 in that string is the duplication the review panel objects to. Brindlecott retains both on the ground that a material class and a surface treatment answer different questions, and that a reader who has only the material code cannot tell whether the sleeve is present.
Three things are, and they are regularly mistaken for a standard covering the clip:
None of the three specifies a clip. None states a diameter, a section, a grip, a service life or a finish thickness for the finished object. The distinction is set out at length in the page on the ISO question, and it is the single point on which the Institute is most often misread.