Blending is the “Holy Grail” of eyeshadow application, and the quality of the blend is entirely dependent on the Density Gradient of the brush head. This is one of the most technically demanding products for a factory to manufacture.
The Science of “The Fluff”
The perfect blending brush must be dense at the base (the ferrule) but incredibly airy and soft at the tip. To achieve this, factories use a Fiber Blend Ratio:
Support Fibers (60%): Thicker, shorter fibers that provide the “backbone” of the brush.
Action Fibers (40%): Ultra-fine, long-tapered fibers that extend beyond the support fibers to do the actual blending.
Tapering Techniques
Factories use two main methods to create the “Dome” shape essential for blending:
Vibration Molding: The hair bundle is placed in a metal cup (the mold) and vibrated at high frequencies until the fibers settle into a perfect, symmetrical dome. This ensures no individual fiber is longer than the others, which would cause “streaking.”
Graduated Layering: Artisans manually layer different lengths of hair before binding them. This creates a “feathered” edge that allows the eyeshadow to transition from high pigment to a “smoke-like” finish on the skin.
Performance Testing
A “Blending Torque Test” is used in QC. The brush is rotated against a pressure sensor; it must maintain its shape without “splaying” (spreading too wide), which would result in a messy application.