Blackened Silver — the dark side of STRUGA

By Dmitry Strugovshchikov, founder of STRUGA

Blackened silver is not a coating or paint — it is the metal's own chemistry, made deliberate. STRUGA treats the surface of 925 sterling silver with a sulfur-based solution, and the dark film that forms is silver sulfide (Ag₂S) together with copper sulfide (Cu₂S) from the 7.5% copper in the alloy — the very same compounds that appear as natural tarnish, only grown with control over depth and uniformity. The film is tens to hundreds of nanometres thick; below it the metal is still real 925, which is why a blackened piece can always be repaired, refinished, or re-blackened.

Updated August 22, 2026

- Blackened silver is 925 sterling silver whose surface is chemically darkened with a sulfur-based solution; the dark layer is a sulfide film grown out of the alloy itself — silver sulfide (Ag₂S) plus copper sulfide (Cu₂S) from the 7.5% copper — not a coating on top.

- The reagent is liver of sulfur, a mixture of potassium sulfide, polysulfide, thiosulfate and bisulfide; the artisan darkens the surface, then selectively polishes raised areas back to bright — dark recesses, bright highlights.

- Below the blackened layer the metal is still real 925, so repair, refinishing and re-blackening remain possible; STRUGA offers re-application as part of lifetime refinishing.

- The film adds no new metals — it is grown from the silver and copper already in the alloy, and STRUGA's 925 is nickel-free regardless of finish.

- With wear, contact points brighten and recesses stay dark; two identical pieces look different after six months on different wearers.

- STRUGA uses both intentional blackening (the Blackened Silver collection) and natural Living Silver patina — the 925 alloy and hand finishing are the same, only the surface treatment differs.

Blackened silver	Figure
Alloy	925 sterling — 92.5% silver, 7.5% copper
What the dark film is	Silver sulfide (Ag₂S) and copper sulfide (Cu₂S)
Film thickness	10 to over 100 nm — colour follows thickness
Reagent	Liver of sulfur, hot bath held below boiling
Blackened objects at STRUGA	17, from 1.6 g to 40 g
Made to order	About two weeks

How blackened silver gets its color

Blackened silver is silver that has been treated with a sulfur-based solution to chemically darken the surface. The active layer is silver sulfide (Ag₂S), the same compound that forms naturally as tarnish — applied deliberately, with control over depth and uniformity, as a design choice rather than a defect.

What the reagent actually is

The working reagent is liver of sulfur — not a single compound but a loosely defined mixture of potassium sulfide, potassium polysulfide, potassium thiosulfate and, most likely, potassium bisulfide. It is capricious. The bath has to be hot but held below boiling: at the boil the reagent breaks down within minutes. Left open to air and light it decays into potassium carbonate and potassium sulfate, neither of which darkens anything — which is why a workshop mixes small and mixes often.

The artisan immerses or paints the solution onto the piece, watches the surface darken to the intended depth, and then selectively removes the darkening from raised surfaces with fine abrasives. The result: dark recesses with bright highlights — the light-and-shadow contrast that defines the aesthetic.

How deep the darkening goes

Depth is measured in nanometres, and the colour reports it. The Sheffield Assay Office describes the same progression that a silversmith watches in the bath: while the sulfide film grows from 10 to 100 nm, thin-film interference paints it in sequence, and only past roughly 100 nm does it settle into the true black of silver sulfide.

Film thickness	What you see	Where it is used
10–30 nm	Warm yellow cast	Barely-there ageing on smooth surfaces
30–70 nm	Red-brown	Antiqued look, warm shadows
70–100 nm	Blue-grey	Cold grey treatment, soft contrast
Above ~100 nm	Solid black	Full blackening — the STRUGA register

This is why «lightly oxidised» and «blackened» are not two products but two stopping points on one clock. The artisan pulls the piece out when the colour is right.

The technical depth of blackened silver

• The dark layer is real silver chemistry. Silver sulfide is structurally part of the metal surface, not a coating sitting on top.
• Depth is controllable. Light treatment produces grey; longer treatment produces near-black. Different artisans calibrate the depth based on the design intent.
• The treatment doesn't seal the metal. Below the blackened layer, the underlying silver is still real 925. Repair and refinishing are possible.
• Selective removal creates contrast. The artisan polishes raised surfaces back to bright while leaving recessed areas dark. This is sculpture, not just chemistry.
• Each piece's blackening is unique. The same design treated by different artisans, or by the same artisan on different days, produces subtly different results. Variation is part of the character.

How blackened silver ages with wear

Over time, the blackened surface interacts with skin contact and ambient conditions:

• Contact points brighten. Where skin touches the silver regularly — knuckles on rings, contact areas on bracelets — friction wears through the surface darkening over months and exposes the brighter metal beneath.
• Recesses stay dark. Areas that don't contact skin retain their darkening almost indefinitely.
• The pattern is unique to the wearer. Two identical blackened pieces will look different after six months on different wearers.
• Re-blackening is possible. If the contrast fades too far, the piece can be sent back for re-application. STRUGA offers this as part of lifetime refinishing.

STRUGA's specific approach

STRUGA uses both intentional blackening (the Blackened Silver collection) and natural Living Silver patina (most other pieces). The choice is design-led: pieces where the design intent is a hard light-shadow contrast get intentional blackening; pieces where the design intent is gradual character development get Living Silver.

What is blackened in the catalog, in numbers

Blackening is not applied across the board here. Of the whole STRUGA catalog, 17 objects carry the blackened finish, and they run from a 1.6 g ear cuff to a 40 g necklace — the Brutalism Ear Cuff V.3 at the light end, the Asymmetric Destroyed Necklace at the heavy one. Between them sit the Brutalism V.3 Ring at 9.6 g and the Signature Cross V.3 at 9.0 g. Every one is made to order in Bali by master silversmiths, roughly two weeks from order to finished object, because the darkening is the last operation and cannot be stockpiled.

The technical approach is consistent across both. The 925 sterling alloy is the same. The hand finishing is the same. Only the surface treatment differs. A buyer who wants to switch a Living Silver piece to blackened, or vice versa, can have it done — both directions are possible through the workshop.

Care for blackened silver

• Gentle cleaning only. Aggressive polishing removes the darkening from intentionally darkened recessed areas.
• No silver-dip solutions. Commercial silver dips strip all darkening — designed for bright pieces only. Will permanently remove intentional blackening.
• Selective polishing only. Use a polishing cloth on the highlighted bright areas if you want to refresh contrast, but never on the recessed dark areas.
• Re-application possible. If the darkness fades unevenly, any competent silversmith can re-apply liver of sulfur to restore the original character.
• Avoid pool water and salt water. Chlorine and salt accelerate uneven wear on blackened surfaces.

This page is about the finish itself — what it is, how it is made, how it moves. Step-by-step cleaning, storage and the oxidised-versus-rhodium comparisons live in the oxidised silver care guide.

The reference object for this finish in the catalog — the Brutalism V.3 Ring, 9.6 g of blackened 925.