Klett 420 Color Scale


FAQ: “Do you know about a scale used for liquid detergents called Klett? Can we measure it somehow on HunterLab equipment?”

The Klett Color Scale, based on the old Klett-Summerson transmission filter colorimeter, is usually used for measuring transmission color of liquids.

This unit can select any of a dozen colored, filters peaking at different points across the spectrum. The most common filter used peaks at 420 nm and is measuring yellowness in clear transparent liquids. This Klett 420 specification has almost faded from industrial use but is still found in a few applications.

HunterLab does not have a correlation to this legacy Klett 420 Color Scale as there is insufficient demand from our customers. Our recommendation for an equivalent and modern metric would be to measure Yellowness Index E313 D65/10 or C/2 in TTRAN Total Transmission using a ColorQuest XT (transparent liquids only) or ColorQuest XE (can be used for multiple products).

HunterLab sphere instruments can measure full L*, a*, b* color, Y Transmission, Yellowness Index, APHA Color and Transmission Haze% can be provided from a single measurement.

A transmission cell of a defined path length (10-mm, 20-mm, 50-mm) and a transmission cell holder will also be needed.

  • C02-1004-481 Transmission Cell Holder
  • 13-8573-40 Transmission cell, 10-mm (best for highly chromatic samples)
  • 04-4592-00 Transmission cell, 20-mm (best for medium chromatic or best for overall)
  • 13-8573-20 Transmission cell, 50-mm (best for low chroma samples)

Measurement Method for Yellowness of Transparent Liquids

  • Standardize the ColorQuest XE in TTRAN mode with the cell (10, 20 or 50-mm) filled with distilled water in the optical path.
  • After standardization, read water as a standard sample as a PQ Performance Qualification step and verify that the YI E313 (C/2 or D65/10) Yellowness Index reads 0, indicating no yellowness.
  • Proceed to make measurements of samples and report the values. Higher YI E3131 values indicate higher yellowness in the sample. The user will define an acceptable range.
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