Color is an important feature of every grease in the marketplace. While it typically does not impart any performance properties (see Never Judge a Grease by Its Color, LubesnGreases Sept. 2016), color is often used as the initial indicator of a products quality by the end user.
When a grease appears to be off-color, it is viewed as potentially contaminated or missing a key component in the formulation and deemed unfit for use. When such color concerns arise, theyre often not due to the quality of the product, but rather the quality of the evaluation method.
Considering the level of sophistication involved in todays grease formulations-from innovations in advanced chemistry to the exacting precision of cutting-edge production processes-its unfathomable that merely eyeballing two samples to compare their color remains the most common way customers evaluate a greases quality upon delivery. Without question, this old-school, industry-wide approach leaves far too much room for error and inconsistency.
Perception vs. Reality
Color and how its perceived have been topics of conversation and study dating back to the days of Pythagoras (left), Aristotle and Plato. However, it wasnt until the 18th century that Moses Harris developed the concept of the color wheel, a means of demonstrating that all colors are composed of combinations of the primary colors of red, yellow and blue.
With this RYB color model, scientists began developing theories on the inner workings of the eye and how colors are perceived. Throughout the 19th century, great strides were made in understanding the anatomy of the eye, which ultimately included the discovery of three types of photoreceptors, each responsible for detecting a particular color.
As a physiological process, eyesight and color perception can vary greatly from one person to the next. The slightest physical or neurological variances between individuals can impact how color is perceived. Factors like age can make the same color appear quite differently to two different people. In fact, even the way one person sees a particular color from one day to the next can change based on their level of stress, fatigue or even their mood.
Beyond differences in physiology, the environment in which an object is viewed can greatly impact how color appears. Most notably, the type and angle of the light illuminating the object can make a dramatic difference. Have you ever noticed how a dark green car might appear black as you view it from various angles? Perhaps youve left the house thinking you were wearing black pants only to discover they were actually dark blue when you walked out into the sunlight.
The human eye is certainly a wondrous apparatus, but with so many physiological and environmental factors affecting how it works, its not the most reliable tool for making important decisions based on color.
Numbers Dont Lie
If color is indeed going to remain a means of comparing a test sample of grease with a quality standard sample, a more definitive method is needed that provides more black-and-white results, so to speak. If youve ever gone to the paint or hardware store with a swatch of fabric to find a matching paint, youre likely already familiar with the technology.
In 1938, Richard Hunter developed the Hunter Color theory, which laid the groundwork for the Hunter L, a, b color space ten years later. Just as the earliest color theories were based on breaking down colors into three components, so too does the Hunter L, a, b space.
In the simplest terms, this methodology is designed to objectively assign numerical values to three elements of a color: L* for the lightness-darkness value, a* for the red-green value and b* for the yellow-blue value. An L* value of 100 would be perfectly white, whereas an L* value of 0 is perfectly black. Positive a* values connote red and negative a* values signify green. Lastly, positive b* values are in the yellow region of the space and negative b* values are in the blue. (See chart below.) Using this method, every color can be converted to numerical values.
To capture this data, the HunterLab company developed a spectrophotometer known as the Hunter ColorFlex instrument. The unit operates by emitting astandardizedwhite light source as a flash onto the surface of the sample being tested. The standardized light source is characterized as D65 by CIE (International Commission of Illumination).D65 is an artificial representation of noon daylight. The sample reflects the light back to the spectrophotometer where a reflectance spectrum is generated and the numerical values are assigned.
To achieve consistent, accurate measurements, proper setup of the equipment is necessary, includingstandardizedanglesof 10 degrees forthe light source and the spectrophotometer. In terms of complexity, however, the Hunter ColorFlex equipment is quite simple to set up, calibrate and run.
A New Tool of the Trade
The ColorFlex works as a means of making accurate, objective and measurable lot-to-lot comparisons. While careful calibration and operation of the equipment by a human being is still required, the tool completely eliminates the guesswork and subjectivity of the final evaluation, an issue inherent in the current method of making a simple thumbs-up or thumbs-down visual comparison.
The Quality Control team at Chemtool Inc. has been incorporating the use of the Hunter ColorFlex instrument to adjust in-process production batches to meet required color specifications with tremendous success. Additionally, when questions about color arise, these concerns can be alleviated using objective L*a*b* data rather than subjective data provided by the customer.
The L*a*b* report contains data that illustrates that the product clearly meets the standard color specifications, which can be shared with customers to quickly put the matter to rest. For instance, since incorporating the test, Chemtool has seen a dramatic decrease in color-related customer questions, with a 70 percent reduction from 2016 to 2017 and on track to achieve another 50 percent reduction by the end of this year.
Imagine a manufacturers entire product portfolio being backed up with solid L*a*b* data, eliminating customer color concerns altogether. Adding up the costs associated with returned off-color products and the manpower and resources spent on remedying those situations, the savings of utilizing the ColorFlex test can be quite significant. Furthermore, while this testing method is all about hard data, the way it can bolster customer confidence and strengthen relationships is immeasurable.
Unlike many related industries, the grease industry currently does not have a quantitative method for determining the color of a grease. Chemtools work demonstrates that the Hunter ColorFlex could be the tool that provides the new method of developing quantitative industry standards. It can be described as a QUECHERS method, meaning quick, easy, cheap, effective, rugged and safe.
The ColorFlex requires a sample size of only 25-30 grams of grease, its nondestructive and takes only about three minutes (including sample preparation) to obtain results. With issues pertaining to color being a prevalent customer complaint throughout the industry, use of the Hunter ColorFlex tool to develop industry-wide standards should be given serious consideration.
Andrew L. Heimer is a chemist and research manager at Chemtool Inc., a subsidiary of Lubrizol Corp., where he oversees all grease R&D projects. He played a leading role in the development of the Hunter ColorFlex machine. He can be reached at Andrew.Heimer@Chemtool.com or 815-389-0370.