950 Pt/Ru vs Pt/Ir: US vs EU Alloys—Which Holds Micro-Pavé Better?

Intro: Micro-pavé depends on extremely small metal beads and thin walls holding tiny diamonds. The alloy under those beads matters more than most buyers realize. Two common platinum 950 alloys — platinum with ruthenium (Pt‑95/Ru‑5) and platinum with iridium (Pt‑95/Ir‑5) — behave differently. Below I explain how those differences affect micro‑pavé setting, longevity, and practical benchwork so you can choose the best alloy for a project.

First, a clear baseline: when you see PT950 stamped, it guarantees 95% platinum by mass. The remaining ~5% can be ruthenium, iridium, or other platinum-group metals. The hallmark does not tell you which one. In practice, many manufacturers in the US and Asia supply Pt‑95/Ru‑5, while several European houses traditionally favor Pt‑95/Ir‑5. Those choices reflect deliberate tradeoffs between hardness, ductility, and color.

How alloying changes metal behavior — why it matters for micro‑pavé

Micro‑pavé uses beads often 0.3–0.6 mm wide, with diamonds that can be 0.5–1.8 mm in diameter. Two mechanical qualities matter most:

• Yield strength / hardness: Higher yield strength resists the metal flowing under daily wear. That helps tiny beads keep their shape and retain stones over years.
• Ductility / toughness: The ability to deform cleanly when a setter pushes or burnishes the bead. Too little ductility and the metal can chip or develop micro‑cracks during setting.

Alloying with ruthenium tends to increase hardness and yield strength more than the same amount of iridium. Alloying with iridium tends to preserve more ductility while still improving strength relative to pure platinum. Those are the core differences that affect micro‑pavé.

Practical differences between Pt‑95/Ru‑5 and Pt‑95/Ir‑5

• Pt‑95/Ru‑5 — the “harder” alloy. Ru is an effective solid solution strengthener in platinum. A Pt‑95/Ru‑5 alloy will typically be noticeably harder and have a higher yield strength than Pt‑95/Ir‑5. That means edges and thin rails resist deformation better over time. For pavé in high‑wear locations (ring shanks, low‑profile collars that rub clothing), Pt/Ru gives better long‑term retention.
• Pt‑95/Ir‑5 — the “more ductile” alloy. Iridium strengthens platinum while retaining more ductility. That makes the alloy more forgiving when pushing tiny beads and burnishing without cracking. For ultra‑fine micro‑pavé with stones under 1.0 mm, or very thin bead walls (0.3–0.4 mm), Pt/Ir reduces the risk of chipping during setting.
• Setting effort and tool wear. Pt/Ru takes more force and sharper tools to shape. It work‑hardens quickly, so setters often need more frequent annealing or to use higher burnishing force. That also means increased burr and tool wear on gravers and burs.
• Long‑term behavior. Pt/Ru beads are less likely to slump after years of wear. Pt/Ir may need slightly larger bead profiles to give the same lifetime retention if subject to heavy abrasion.
• Color and finish. Both alloys remain white. Iridium tends to produce a slightly brighter, whiter surface; ruthenium can give a touch more gray. Practically this is only noticeable to a trained eye and does not affect stone appearance.

Which is better for micro‑pavé?

The honest answer is: it depends on stone size, wall thickness, and where the pavé sits.

• For very small stones (0.5–1.0 mm) and feather‑thin beads (0.3–0.4 mm): Pt‑95/Ir‑5 is often preferable because the alloy is more ductile. Setters can form consistent, clean beads without hairline cracking. The immediate fit and finish will be superior, and fewer stones will be damaged during setting.
• For slightly larger pavé stones (1.0–2.0 mm), higher wear areas, or very fine rails that must resist abrasion: Pt‑95/Ru‑5 gives better long‑term stability. Its higher hardness keeps beads from flattening and stones from working loose over years.
• When in doubt: If the job is high‑value but exposed to heavy wear (rings, bracelets), favor Pt/Ru. If the job is extremely delicate—very small stones in a fine head or openwork setting—favor Pt/Ir for safer hand‑setting.

Bench tips and best practices

• Always get the mill certificate: ask the supplier for composition and mechanical properties (Vickers hardness, tensile/yield, elongation). Don’t rely on the PT950 stamp alone.
• Make test strips and set practice stones. Do a burnishing test and a simulated wear test (ultrasonic, tumble, or manual abrasion) to check retention.
• If you use Pt/Ru for micro‑pavé, consider slightly beefing bead cross‑sections by 0.05–0.1 mm to ensure long‑term security without changing the visual scale.
• Control annealing: Pt alloys work‑harden quickly. For Pt/Ru you may need more frequent local anneals, but avoid over‑heating large areas which alters grain structure and finish.
• Choose burr sizes carefully. For micro‑pavé with 0.5 mm stones, start with a 0.6–0.65 mm cup and adjust for the alloy’s flow characteristics.

Final takeaway

If you need pure long‑term wear resistance and a slightly harder seat, Pt‑95/Ru‑5 is the better choice. If you need maximum setting control, minimal risk of metal chipping while forming tiny beads, and a smoother hand‑setting experience, Pt‑95/Ir‑5 is preferable. Neither alloy is universally “best” — the right choice depends on stone size, bead thickness, and whether short‑term setting ease or decades‑long wear is your priority. Always test the exact alloy batch before committing it to fine micro‑pavé work.