Do you trust your eyes fully? Look at a photo with two gray squares. Is it easy for you to believe that they are of the same shade of gray? If you cover the middle seam with your finger, you can see that they are, in fact, the same shade. It is not our eyes causing the illusion. Rather, it is the brain’s processing of the information received from the eyes. Our brain is a fascinating organ, but it is not without its flaws. Outside and inside influences can affect the way the brain processes the information it receives. These influences can be environmental, such as lighting, background colors, etcetera. Within the optical system itself, things such as retinal fatigue, retinal damage, color deficiency, age or even dietary influences can change how our brain processes color and light. So after reading this, I can ask again: Do you trust your eyes fully?

When it comes to evaluating cleanliness of abrasive blasted metal, all the above factors can have the same effects. I routinely have the opportunity to visit many facilities that are involved in the coating process. One thing I can assure you from all those visits, is that one person’s SP5/NACE 1/Sa3 is SP10/NACE 2/Sa2.5 for someone else and vice versa, even within the same facility.

So why not adapt modern technology to perform this evaluation process and get more consistent results? Removing all the influences that effect our brain’s perception of color leads to more reliable measurements.

Enter spectrocolorimetry. Using the process of shining the three primary additive colors (red, green and blue) and combining the reflected light into a gray scale, you can accurately measure the level of cleanliness on blasted metal without all the outside influences that can affect the reading.

When it comes to light, there are three primary colors, red, green, and blue. If you had the old-school cathode-ray tube color tv’s growing up, and you looked really close at the screen (despite the warning from your parents), you would’ve seen those these colors. With these three colors of light, you can make up every possible color of the visible light spectrum, by adding different combinations. For this reason, these are called additive colors in reference to light.

Looking at the globe, it is a depiction of every possible color combination using the three primary additive colors of light. Now notice the north and south poles. They represent 100% of all 3 colors (pure white) or 100% absence of all those colors (black). For the purposes of measuring cleanliness on blasted metal, we only care about this axis. If you take that axis and split it into 100 equal segments, you have a 0-100 gray scale. This is the reading the spectrocolorimeter (WA Clean) presents.

Keep in mind, this technology is in no way meant to replace the Coating Inspection Professional who trained and tested through the professional organizations. Rather, it is meant to make their job easier by removing the environmental factors that can affect their personal perception of cleanliness.

If you would like to learn more about how spectrocolorimetry can help you in your blast operation, please feel free to reach out to me or your local Winoa rep.

Contact: chris.prouty@winoa.com

Contributing Editor for MFN and Technical Advisor at Winoa