Delta E & Why It Matters

In the world of plastic color matching, Delta E (ΔE) is the standard measurement for color difference—and one of the most important metrics for quality control. But what does it actually mean, and why should processors and OEMs care?

Delta E is a numerical value that represents the difference between two colors in a perceptual color space. It quantifies how much a sample color deviates from a target standard.

• ΔE = 0 means the colors are identical.

• ΔE < 1.0 is virtually indistinguishable to the human eye.

• ΔE 1–2 is considered acceptable in most industries.

• ΔE > 3 is easily noticeable and usually considered a mismatch.

Delta E is calculated using spectrophotometers that capture a color’s position in three-dimensional space—typically using the CIE Lab* color model. This allows for precise, repeatable measurement beyond what the eye can see.

• Line Speed Variability
  Faster or uneven extrusion speeds can affect pigment distribution, leading to inconsistent color bands.

• Melt Temperature Fluctuations
  Even slight temperature inconsistencies can alter color, especially with heat-sensitive pigments.

• Back Pressure and Screw Design
  Poor mixing due to improper screw design or settings can lead to streaking or uneven dispersion.

• Shear Heat During Injection
  High shear rates can degrade pigments or alter their tone.

• Hot Spots in Mold Cavities
  Uneven mold cooling can cause color variation from part to part.

• Short Shot or Flow Marks
  Improper fill can create visible color distortions or swirls.