Gloss/color - How much does gloss affect the appearance of color?

[gpainter]

How much does gloss affect the appearance of color? I was told that a 10 gloss unit difference may make the color match appear different(lighter/darker, even if the color matches) to the Customer's eye. Any color/gloss experts?

[Jim Wynne]

Originally Posted by gpainter

How much does gloss affect the appearance of color? I was told that a 10 gloss unit difference may make the color match appear different(lighter/darker, even if the color matches) to the Customer's eye. Any color/gloss experts?

The angle of reflectance is a critical component in gloss and color evaluation. In all cases where color matching is important, it's critical to specify the rules for evaluation, including angle of viewing and the light source to be used. You can find some good information on this subject by Googling for "gloss vs. color" (without the quotes).

[tomvehoski]

Not an expert, but many factors, including gloss, will affect perception of color. Back when I worked with paint we had constant accept/reject/accept again/reject again.... fights because we did not have clear evaluation techniques. Designers would pick a color based on a pantone chip, then be upset when it did not look the same painted on plastic, steel, in powdercoat, etc. Quality would approve components later to have the shop floor question because they did not look the same as other components - shop lighting was not the place to inspect color.

Make sure you have a clear specification for how color is to be checked - light booth, spectrophotometer, etc. and that both sides agree.

[Adriane]

In my limited experience, the higher the gloss (the smoother the surface) the darker the color. A sample with a higher gloss would appear darker than an identically colored sample at a lower gloss.

As was said before, the angle of observation does play into the exact measurement of gloss. A good spectrophotometer allows you to view from a variety of angles. But to the naked eye the above is a general rule.

Adriane

[wslabey]

Originally Posted by Adriane

In my limited experience, the higher the gloss (the smoother the surface) the darker the color. A sample with a higher gloss would appear darker than an identically colored sample at a lower gloss.

As was said before, the angle of observation does play into the exact measurement of gloss. A good spectrophotometer allows you to view from a variety of angles. But to the naked eye the above is a general rule.

Adriane

Welcome to the world of subjective evaluations always over-riding measurement tools. With all the tools available to measure color and paint quality it still ends up being subjectively reviewed by the customer in daylight.

[Craig H.]

Try this link:

http://www.goldenglowpaints.com/Arti...cles/GLOSS.htm

Also, Technidye has a good explaination of the C.I.E. colorspace on their web site. If you ever get a chance to go to their seminar, it is worth the time. And, no, I don't own stock.

[Randy]

As a painter of cars (commercially) in days gone by I recall that gloss adds depth to the color as opposed to darkening it (actually a touch of black in white paint deepens the white). You need to have a dark base to begin with that can be "roughened up' prior to the overlay of your gloss coats. Some folks liked to sand every coat of gloss as well, but I found that sanding every other coat really made the colors deepen (darken) and bust out. A viewing perspective of 90+/- a couple degrees was normally the optimum for full color richness (acute angles tend to reflect too much "white" light thereby lightening the color.

At least that's what I remember....Oh yeah, we used DuPont materials exclusively.

[Scott G]

I am no color expert, but use a color spectrophotometer a few times a month to evaluate color in plastics.

There are several types of spectrophotometers with the 45°/0° and the spherical being two of the most common. The 45°/0° will take gloss into consideration and will call two samples of different textures different colors due to the gloss / even if they are the same pigments.

The spherical spectrophotometer has two ways of evaluating color spectural included or excluded (SPIN and SPEX). This is how it compensates for gloss. Measuring in SPIN mode the spectrophotometer will detect changes in color regardless of changes in gloss. SPIN mode allows us to compare the color of a glossy paint chip to a dull matte finished plastic. SPEX mode is similar to the 45°/0° results.

The spectrophotometer converts light (color reflectance) into a mathematical formula (CIE LAB or other scale). It compares hue, saturation, lightness / darkness and plots the values on a 3-d graph. The results are then reported as a delta E value. In plastics the typical specs require a SPIN delta E value of less than 1.

When we first started using a spectrophotometer I was curious about how gloss would effect measurements. I took a molded texture sample plaque and compared different texture samples. This plaque was on one solid piece of plastic with multiple textures. I compared a rough texture to a polished glossy texture. SPIN mode was slightly influenced by the texture and reported a Delta E of less the 0.1. SPEX mode on the other hand reported a Delta E of over 7.

So even though the two textures sampled were identical in color visually the glossy sample looked darker and the SPEX mode confirmed this.

Debating color with vendors / our production / and customers is hard, because even using CIE LAB scale color can be subjective. Sometimes a color can have a Delta E value of over 2 but to the eye look like a close match, other times a Delta E of 1 looks like a horrible match.

One major aerospace customer of ours uses a spectrophotometer only to confirm what the eye has told the Inspector. The default is to look at the color match in a light booth under 6500 Kelvin lighting and only use a spectrophotometer in SPIN mode if the Inspector visually rejected the color match.