How to Determine Dry Optical Pigment Loading for Custom Automotive Finishes

Selecting the right dry optical pigment loading is an important step in creating custom vehicle finishes using optical pigments for automotive coatings. The amount of pigment added can affect effect intensity, the contribution of the base color, and the practical application performance of the coating system. This guide explains the key factors that influence dry optical pigment loading decisions in custom automotive finishing.

1. Pigment Coverage on the Surface: Balancing Effect Visibility and Basecoat Contribution

Dry optical pigment loading determines how much the pigment layer influences the final automotive finish. Higher loading increases pigment presence on the surface, while lower loading allows more contribution from the underlying basecoat.

For PVD optical pigments, loading also affects particle distribution and orientation within the coating film. Excessive pigment concentration may reduce the spacing between individual particles, affecting optical alignment and the consistency of the final effect.

In a BOSCOM Pigments application test, OP10101 Ruby Scarlet, OP40101 Emerald Green and TP60101 Ocean Sapphire were applied on black speedshapes at 0.15% and 4% loading levels.

The comparison demonstrates how loading level changes the relationship between the optical pigment layer and the black basecoat. At lower loading, the dark background contributes more strongly to the final appearance, while higher loading creates a more pigment-dominant effect.

2. Pigment Form: Why Flakes and Powders Require Different Loading Levels

The physical form of dry optical pigments influences the loading level required to achieve the desired automotive effect. Optical flakes have a thin platelet structure and high surface area, allowing them to create strong reflective effects at relatively low addition levels. Powder-type optical pigments generally require higher loading to achieve a similar level of visual impact.

As a general reference, custom coating applications may use around 10 g/gal for optical flakes, while powder optical pigments are often used around 25 g/gal, depending on pigment type, coating system and target appearance.

3. Basecoat Selection: How Background Color Influences Optical Pigment Loading

Basecoat color is an important consideration when determining dry optical pigment loading because the background layer affects how strongly the optical effect is expressed. For translucent optical pigments, especially color-shifting effects, the basecoat can significantly influence the final color appearance by changing contrast, depth and color transition.

Darker basecoats, particularly black, usually provide stronger contrast and allow optical effects to appear more vivid at lower loading levels. Lighter or metallic basecoats create different reflection and color interactions, which may require loading adjustments to achieve the desired effect strength.

For this reason, the same optical pigment may require different loading levels depending on the selected basecoat. Understanding the relationship between base color and optical pigment appearance helps custom automotive professionals select appropriate pigment concentration for different finish designs.

4. Vehicle Geometry and Surface Curvature: Adjusting Loading for Custom Finishes

Custom automotive finishes are not evaluated on flat panels alone. Body shape, surface curvature and viewing angle changes all influence how optical pigments are perceived after application.

In the custom paint industry, terms such as color travel, flop, sparkle movement and visual impact are commonly used to describe how an effect changes across different areas of a vehicle. These characteristics become especially important on highly curved surfaces, including motorcycle tanks, fairings and sculpted custom body panels.

Optical pigments create their appearance through angle-dependent light interaction. On a flat panel, the viewing angle changes are relatively limited, while curved surfaces continuously expose different areas of the coating to different viewing angles. This can make color-shifting effects, brightness changes and reflective movement appear stronger across the surface.

For example, a color travel pigment applied on a motorcycle fuel tank may show more dramatic transitions because the tank shape creates continuous angle changes across a relatively small area. In contrast, a large flat automotive panel may display a smoother and more controlled effect.

Therefore, loading decisions for custom finishes are often adjusted based on the desired visual balance. Higher pigment loading can increase effect intensity and visual impact, but on highly curved surfaces it may also create stronger transitions and a more aggressive appearance. Lower or more controlled loading can help maintain a smoother effect across complex body shapes.

5. Spray Equipment and Nozzle Size: Defining the Practical Loading Range

Spray equipment influences the practical loading range of dry optical pigments. The effects of spray application may require adjustments to pigment concentration depending on the spray system, nozzle size and application purpose.

Therefore, loading should be selected not only for optical intensity but also for whether the pigment mixture can be applied consistently with the selected spray equipment.