FAQ: “I work the test laboratory where our QC department has recently purchased a ColorFlex EZ 4500L. Could you tell me if it is possible to measure light reflective values using this equipment, particularly for metal plates with various finishes such as bronze, stainless steel and polished chrome for example. Please find attached an image of the metal plate with a stainless steel finish. We are trying to measure the LRV of this plate.”
In color science there are rules or guidelines for how different types of materials should be measured for color and appearance. However, one of our main rules for color measurement applications is that “for every rule, there is a counter-rule… and sometimes 3 or 4 variations”.
The rule for measuring bare metal surfaces where the color is visually seen in the specular reflectance or shine off the surface is to measure the color on a diffuse d/8 sphere instrument such as the HunterLab UltraScan VIS.
Your situation offers the counter-rule which states that while a diffuse sphere is the optimal choice, a directional 45 degree illumination/0 degree viewing geometry instrument may be used if the plating surface is sufficiently roughened to spread the color signal into the collection angle of the ColorFlex EZ.
The first step is to verify you can get a repeatable measurement of the plated metal using your ColorFlex EZ 45/0 directional sensor.
- Standardize the CFEZ using its black and white standards.
- Take 2 or 4 readings of the plate, preferably in different locations, rotating the plate 90 degrees between each reading.
- Average and report the result.
- Do this 3 times on the same sample and verify the average measurement is repeatable.
Take a plate sample that is visually different (lighter/darker; more/less red; more/less yellow) from the first and measure it using the method above.
Verify the plate sample differences to the plated standard correspond to the visual differences.
If this works, you have a viable method of measuring your plated sample using the directional ColorFlex EZ 45/0 LAV that should work for most plated surfaces except for the most mirror-like where a sphere instrument will be required.