Merck Iriodin Pigments Alternative — Silver White Series

Iriodin from Merck has long been the reference line for this category. Many formulators have built their color standards around it. But lead times, pricing volatility, and MOQ constraints push technical teams to qualify alternatives — without compromising on the performance parameters that matter.

Kolortek's KT-100 (natural mica) and KT-7100 (synthetic mica) series were developed with that substitution scenario in mind. Particle size distributions, substrate types, and coating compositions are aligned to the Iriodin reference grades. In practice, side-by-side evaluations show comparable goniometric profiles for most grades — though, as with any substitution, your application and dispersant system will determine final performance.

KT-100 Series — Natural Mica Substrate

The KT-100 series covers the standard range of silver-white effects on natural mica. These are anatase or rutile TiO₂ coatings depending on the grade — the distinction matters for weather resistance and brightness. Rutile grades (those with tin oxide in the coating layer) deliver higher refractive index and better exterior durability.

KT-7100 Series — Synthetic Mica (Fluorphlogopite) Substrate

Synthetic mica — fluorphlogopite — is worth specifying when the application demands higher purity, cleaner color, or elevated temperature stability. Natural mica carries trace mineral impurities that can introduce a faint yellowish cast and occasional dark specks; synthetic mica eliminates most of that. The difference is subtle in mass-tone but more visible in fine-particle grades or highly transparent systems.

For high-temperature plastics processing or exterior architectural coatings, the thermal stability advantage of the KT-7100 series is a genuine differentiator — not a marketing claim.

Application Fit

These grades are suitable across a broad application range, though the appropriate particle size range shifts significantly depending on the process and substrate.

Paints & coatings: Mid-range particles (10–60 μm) are the standard choice for solventborne and waterborne decorative coatings. Rutile grades handle exterior exposure better than anatase. In metallic effects, blending with aluminium paste can push brightness while the pearlescent component maintains the white-silver undertone.

Printing inks: Fine-particle grades (<15 μm) are the practical choice here. Anything coarser causes plate wear, rheology issues, and inconsistent lay-down. KT-110, KT-111, KT-7101, and KT-7121 are the grades to evaluate for gravure and flexo.

Cosmetics, soap, and nail: Both mica series are applicable where formulations allow. Synthetic mica grades are often preferred in leave-on cosmetics given their cleaner profile. Consult applicable regional regulatory frameworks for your specific end-use.

Epoxy flooring and countertop / artificial marble: Coarser grades — KT-154, KT-163, KT-183, and the large-particle KT-7100 series — work well here. The particle size contributes directly to the visual depth and sparkle dimension in clear epoxy layers. Uniformity of dispersion matters more than concentration at this end of the particle size range.

Craft applications: The broader sparkle grades offer maximum visual impact at low loading levels, which suits hand-blended or small-batch craft media.

Performance Characteristics Worth Knowing

The optical effect of these pigments comes from specular reflection and partial transmission through the TiO₂-coated mica layers. In practice, this means the effect is highly angle-dependent. Viewing geometry matters — what looks bright silver at 45° can appear translucent white at high angles. This is expected behavior, not a defect.

When blending with transparent colorants or dyes, the base pearl color carries through but is tinted by the colorant — a useful technique for pastel metallic effects. Blending with carbon black shifts the appearance toward silver-grey metallic, often more convincing in automotive or industrial contexts than a straight silver pearl alone.

Rutile grades (those containing SnO₂ as a nucleating agent for the rutile TiO₂ phase) offer meaningfully better UV stability and are the appropriate specification for exterior or sun-exposed applications. Anatase-coated grades are fine for interior or non-UV-exposed use cases where the brighter, slightly cooler white tone is preferred.

Synthetic mica grades are stable to higher processing temperatures than natural mica equivalents — relevant for engineering plastics or powder coatings processed above 200°C.

Formulation and Handling Notes

Pearlescent pigments are shear-sensitive. High-speed dispersers, bead mills, and ultrasonic processors will fracture the flakes and reduce particle size — killing the sparkle effect. Low-shear mixing, gentle paddle or anchor agitation, or direct addition late in the process are the right approaches for most systems.

Typical loading levels run 2–8% in coatings and inks, and up to 15–20% in epoxy or polyester casting applications. Higher loadings in transparent systems can produce the "layered stone" appearance used in artificial marble effects.

These pigments are chemically inert under normal use conditions and compatible with most resin systems — polyurethane, epoxy, acrylic, alkyd, polyester, and nitrocellulose. Wetting agents can improve dispersion in waterborne systems where the pigment surface may need some treatment to reduce flotation or sedimentation.

Worth noting: larger particle grades (above 100 μm) will settle in low-viscosity systems. Thixotropic additives or gel-phase pre-dispersion helps maintain suspension in liquid applications.

Frequently Asked Questions

Q: How close is the match between these grades and the corresponding Iriodin effect equivalents?

A: For the directly mapped grades — KT-100 vs. Iriodin 100, KT-103 vs. Iriodin 103, KT-151 vs. Iriodin 151