Gold Bronze Pigments

Technical Description

Gold bronze pigments belong to the metallic pigment category alongside aluminum paste and copper powder. The base material is a copper-zinc alloy — brass — with the zinc content adjusted to shift the color from reddish-copper (high copper, low zinc) toward pale gold (higher zinc). Tin is included as a minor alloying element in some grades, providing additional hardness and contributing to color stability. The alloy is mechanically milled into flat, leafing or non-leafing flakes, with the milling conditions controlling particle size, flake thickness, and the resulting color and luster characteristics.

The surface chemical treatment applied during or after milling serves two functions: it passivates the reactive copper surface to slow oxidation, and it controls whether the pigment is leafing (flakes float to the surface of the coating film, forming a continuous metallic layer) or non-leafing (flakes distribute throughout the film depth). Leafing grades produce a more mirror-like, high-opacity metallic surface; non-leafing grades produce a metallic effect with more depth and transparency. The choice between leafing and non-leafing is a formulation decision that affects both appearance and performance.

Unlike mica-based pearlescent pigments, gold bronze pigments are opaque and electrically conductive. They provide strong hiding power and a warm, saturated gold metallic appearance that mica-gold pearlescents — which achieve their gold color through iron oxide interference — do not replicate. However, the copper content means they are subject to oxidation in aggressive environments and should not be used in alkaline systems without confirming compatibility, as copper alloys are susceptible to alkaline corrosion.

Particle size in mesh refers to the sieve opening through which the powder passes: 200 mesh (approximately 75 µm opening) is a coarser grade suitable for screen printing and decorative coatings; 1500 mesh (approximately 10 µm opening) is a fine grade suitable for gravure inks, flexo, and applications requiring smooth film formation. Finer grades generally produce a smoother, more satin metallic finish; coarser grades produce more visible individual flake reflections and higher luster intensity.

Key Features & Benefits

Note: Copper-zinc alloys are electrically conductive. Not suitable for applications requiring electrical insulation. Confirm compatibility with alkaline formulation systems before use, as copper alloys can react with strongly alkaline media.

Applications

Mesh-to-micron conversion is approximate and varies by measurement standard. Contact us for particle size distribution data by grade.

Industry Solutions

Gold metallic effects in coatings and inks can be achieved through two fundamentally different material types: mica-based gold pearlescents (iron oxide coated mica) and copper-zinc alloy bronze powders. Each serves a different visual and performance requirement, and specifying the wrong type for the application is a common and costly formulation mistake. Mica-gold pearlescents produce a semi-transparent, pearl-depth gold with angle-dependent shimmer. Bronze powders produce an opaque, high-coverage warm metallic gold with a continuous surface appearance. For applications where the design intent is a solid, opaque gold — high-end packaging print, decorative furniture lacquer, traditional gilding effects — bronze powder is the technically correct choice, and mica-based alternatives will not achieve the same coverage or color saturation regardless of loading level.

A secondary challenge is oxidation stability: untreated copper-zinc powder darkens and loses luster on exposure to air and moisture, which limits shelf life and in-use stability in water-based formulations. Surface treatment quality is therefore a meaningful differentiator between suppliers, but it is rarely quantified by manufacturers without buyer inquiry.

Kolortek's Gold Bronze Pigment series uses copper-zinc alloy with surface chemical treatment specifically to address the oxidation stability issue — the treatment passivates the reactive copper surface to slow tarnishing and extend usable formulation life. The series covers the full mesh range from 200 to 1500 mesh, allowing buyers to source coarse decorative grades and fine ink grades from a single supplier with consistent alloy chemistry. Both leafing and non-leafing grades are available, so formulators can select the film-formation behavior appropriate for their coating system without sourcing from a secondary supplier. With 20 years of effect pigment manufacturing experience, Kolortek maintains consistent alloy composition and surface treatment quality across production batches — the two variables that most directly affect color tone consistency and oxidation resistance in bronze pigment applications.

Samples by color tone and mesh grade, leafing/non-leafing grade options, TDS and SDS, and pricing are available upon inquiry. Contact Kolortek's technical team with your formulation system type, target color, and mesh requirement for grade-specific recommendations.