What Are Pearlescent Pigments? 

Pearlescent pigments are partly translucent powders formed by depositing titanium dioxide and/or iron salts onto mica, layered with metal oxides.¹ They provide fascinating visual effects and color to a range of coatings, plastics, and printing ink. These shiny pigments are translucent and easily reflect light because of their smooth surface. The luster of light reflected off the platelets changes depending on the size of the piece. Smaller particles typically have a satin sheen, while bigger ones tend to have glitter or in some cases sparkles.

Substrate-free pigments and layered pigments are the two most common types of pearlescent pigments. Pigments in the first instance are made up of only one optically homogeneous substance, whereas pigments in the second case are made up of at least two optically distinct materials. The two-layered style of pigments is represented by natural mica with thin layers of various metal oxides. The mica-based pearlescent pigment was originally created in the 1970s, and its development was accelerated up to the 1990s when multilayer mica systems were effectively achieved.²

As pearlescent pigment suppliers, our products are of the highest quality using solid manufacturing practice, and their features and benefits are outlined below, including a background to pearlescent pigments, how they work, and certain restrictions you should be aware of.

Substrate-Free Pearlescent Pigments

Natural pearl luster, basic lead carbonate, bismuth oxychloride, micaceous iron oxide, and TiO2 flakes are the most common substrate-free pearlescent pigments. Natural pearl essence is a pearl pigment dispersion made up of high-aspect-ratio platelet-shaped particles extracted mostly from fish scales or skin. Guanine makes up 75-97 percent of these particles, whereas hypoxanthine makes about 3-25 percent. There is currently no commercial synthesis of this pigment, therefore natural pearl essence manufacturing is solely dependent on natural supplies. This pigment is highly costly, yet it has certain unique properties, like low brittleness, a high and soft sheen, and a low density.

Considering the benefits and drawbacks of this pigment powder type, it is mostly employed in high-end cosmetic applications.

Layered Pearlescent Pigments

The dominant class of a pearlescent pigment is represented by natural mica coated with thin films of different metal oxides. Natural muscovite mica is a very affordable crystal that can be easily split into smaller flakes of about 250 nanometers. Mica pigments swiftly monopolized the special effect pigment industry due to these advantages, capturing 90% of the total market. The deposition of metal oxide layers on the mica surface is a simple way to make this pigment.

How Do Pearlescent Pigments Work?

The term ‘white light’ refers to light that encompasses all colors of the spectrum. You will notice the reflection of blue light when you view something like a blue pigment. Similarly, you will notice the reflection of red light when you observe a red pigment.

Mica platelets are transparent to a high degree, allowing white light to travel through the platelet. The refraction index of the titanium dioxide layer is greater than that of the mica and the surrounding area. Light is refracted and reflected in various angles at contact.³ The interference color – the fundamental characteristic of a pearlescent effect, is formed as a result of this phase shift. Even in tiny layers on a mica substrate, iron oxide takes on its distinctive color.

Formulators may fine-tune the reflection of certain wavelengths of light by manipulating the metal oxide and its thickness, resulting in personalized and distinctive colors. But even small modifications in the platelet can have a significant influence on the pigment and apparent colors.

Key Characteristics

The luster and appearance of a final coating are influenced by several elements. Among the most significant are flake orientation, particle size, pigment concentration, and coating film transparency.⁴

• Particle Size – Pearlescent pigments are available in a variety of particle size ranges. Coatings’ luster, coverage, and appearance will be influenced by their size.
• Flake Orientation – Only when the platelets are consistently orientated parallel to the substrate, can maximum reflection and color travel be attained. This is accomplished mostly by film shrinkage and coating leveling when the coating dries. The size of the particles might also have an impact.
• Pigment Concentration – While a specific quantity of pigment is required to provide a color effect and adequate concealment, using too much pigment may actually damage the overall appearance. When too much color is introduced, the pigment particles collide and hinder platelets from freely orienting, resulting in a loss of shine and a dull appearance. Edge scattering is another element to consider. Edge scattering occurs when light scatters off the platelet’s edge, increasing diffuse reflection rather than dazzling, specular reflection. The ideal pigment loading is 10-20% pigment based on the total solids of paint. To achieve delicate, soft effects, use a smaller quantity. In order to get a pearlescent look over a colorful base coat, it may be more cost-effective to use less pigment (1-1.5 percent).
• Film Transparency – Because of the optics of pearlescent pigments, it’s critical that light passes through the film without being impeded. As a result, any pigment or additive that adds opacity to the film or reduces light transmission (i.e. light scattering) will decrease or destroy the shine. Pigmentary titanium dioxide, calcium carbonate, and talc are among examples. 

Uses And Restrictions

A mica based pearlescent pigment is exempt from certification and may be used as a color additive in foods in amounts up to 1.25 percent by weight in cereals, confections and frostings, gelatin desserts, hard and soft candies (including lozenges), nutritional supplement tablets and gelatin capsules, chewing gum and even to create impressive drinks. For celebrations, it can be used to create cocktails in amounts up to 0.07 percent by weight in distilled spirits containing not less than 18 percent and not more than 25 percent alcohol by volume[1].

They can also be safely used to color ingested drugs in quantities up to 3 percent by weight of the final drug product. The maximum amount of iron oxide to be utilized in the manufacture of these pigments is not to exceed 55 percent by weight in the finished pigment – this is in accordance with the Code of Federal Regulations.¹

Summary 

A pearlescent pigment is a flexible type of effect pigment that may be utilized in a variety of coatings. Because of its unique physical structure and composition, its color is caused by light interference. Mother-of-pearl effects and fascinating color journey combinations are created by their semi-transparent nature and specular reflection. Pearlescent pigments come in a variety of sizes and colors, and they’re simple to make and apply if you follow a few simple guidelines. If you would like a sample of any pearlescent pigments, be sure to contact us today.

References:

1. https://iacmcolor.org/color-profile/mica-based-pearlescent-pigments/

2. https://encyclopedia.pub/805 

3. https://www.pcimag.com/articles/105225-pearlescent-pigments-in-coatings-a-primer

4. https://www.naturalpigments.com/artist-materials/pearlescent-pigments-how-they-work/