Monday, November 1, 2010

Understanding the Language of Color

As a manufacturer of 3DL Doors or components you are probably used to seeing color matches of solids and woodgrains. On occasion you may have even had a manufacturer to color match some item for you.

In this article I will delve into the technical side as it relates to color matching and color control. I will explain more about why different sources of light affect the color and cause metamerism and I’ll mention a lot of interesting facts such as how the size of a sample can actually change your perception of the color.

Since most people selling doors, components or Kitchens utilizing 3D Laminate thermofoils are selling color I think that there may be new and interesting facts as it pertains to colors.

There are three things that have the biggest impact in matching a 3D Laminate; the print, the texture and the gloss level. One interesting point is that under normal viewing conditions a sample with a higher gloss level will generally appear darker than a sample with a matte surface. This means that when matching colors it is critical to not only match the design but the gloss level needs to be similar. It also means that if you are working with two different products such as a melamine board and a 3D Laminate which has a different texture you will need to make some consideration in regards to how the different textures are contributing to the color.

When I visit a customer or when I am managing our sales staff I ask questions such as :

1. Who is the decision maker? Purchasing, Management or their client?

2. Does the decision maker have a window in their office and to which side is the window facing their desk?

3. Does the decision maker have flourscent lights or incandescent?

4. Does the decision maker hold the samples up in front of their face or look at them laying on their desk?

5. Does the client want ticking texture or a different texture than the target color?

The above questions are critical to being a good color matcher because all of these small things play into the quality of the match as I’ll describe below.

The surface texture will dramatically change the gloss level and affect the perceived color. An interesting pont is that the human eye is more critical of any color difference in a smooth texture than in a rough texture. So if a customer asks us for a smooth emboss on a solid color then it means that the accuracy will be more fragile. When matches are made to HPL (High Pressure Laminate) or TFM (Thermofused Melamine) typically there are various things that cause the materials to look differently. Firstly the process of impregnating papers with melamine resins can create a bit of a haze. Secondly the texture used on the press plates is often different that the embossing rollers used in a 3DL (3D Laminate). This affect is called metamerism. There are various definitions of metamerism however I feel the most accurate for our purpose is: “a metamerism occurs when the color standard and the submit do not match under all lighting conditions. This means that a solid color fabric when viewed under two different lights in a commercial light box, will appear to cast two different colors.”

Texture is the biggest refractor of light and this is the key source of metamerism. So the key point here is that the target match (paint, TFM, or HPL) typically is different than the surface texture of the 3DL so the match complication is dramatically increased. So for any manufacturer of steel, laminate, paint, carpet or whatever surface manufacturer, the difference in processes between manufacturers is a key complication in color matches.

Color – The Fundamentals
Since 3D Laminates are a plastic for you to better understand colorants it first requires basic knowledge of how color works for plastics. Color is not an absolute property as the perceived color of an object is dependent upon three elements. The elements are Illuminate, Observer and Object.

The illuminant used will affect the perceived color dramatically. Perception of color is unique as the human eye perceives colors differently under various light sources. The perceived color under a fluorescent light is different than that perceived under an incandescent light, and they will both be different to that perceived in daylight. Keep in mind that daylight is one of the most uncontrolled and variable sources of light, and will vary with time of day, weather, orientation, etc.

Perception of color requires an observer (either human or instrumental). What most people are unaware of is that every individual has a unique and different sensitivity to color that may be biased slightly towards a specific color. So they may be unaware that they believe a color is a good or poor match however the general population may in fact that it is a good match. This does not mean that they will always get it wrong but it can mean that as an individual you may perceive maples or yellow toned colors inaccurately however for cherries or solid whites your eye is highly accurate (based upon the populace). An interesting fact is that Men are approximately 16 times more likely to be color deficient than women. Approximately 8% of men and 0.5% of women have some degree of inherited color deficiency (200 million people worldwide). Red-green color deficiency is a hereditary disease, carried by the X chromosome of females. For this reason the daughter of a color deficient father can pass it to her sons. Women have two X-chromosomes and one defective X chromosome will be compensated for by the other non-defective. The chances of having two defective X-chromosomes are small.

Aside from men being 16 more times likely to be color blind, researchers have also found that there are in fact differences between men’s eyes and female’s eyses. As you may know humans have 3 different type of cone cells in our eye. Our eyes perceive color basically the opposite of a TV set. On a TV there are different color dots of red, green and blue. In the eye, con cells also have three different photo pigments that are generalized as red, green and blue but actually they are yellowish green, green and bluish violet.

What researchers have discovered was that over 50% of all women posess a fourth photo pigment that makes women more adept at detecting subtle spots of red light.

So in conclusion, women (on average) are superior at more accurately detecting colors.

Most are unaware that the target or object may appear to be relatively constant but in actuality the color perception can vary within an object. So large areas of a color appear brighter than small areas of a color. If a target is a solid white HPL that is 2 square feet the absorption of light will affect the perception to make the sample appear lighter than if a 3” X 4” color sample is used. That is why factories who produce color maintain internally strict color matching procedures such as the size of samples they are evaluating. This is called (the area effect). The next time you show a client your color match try to present samples of the same size so the customer can more accurately perceive the colors.

Colors will actually appear duller when in front of a bright background than when in front of a dark background. This is called (the contrast effect)

The next is that colors will appear different when viewed from different angles or when illuminated from different angles. This is called (the directional effect).

So image when a sales person presents a color match to a client and the light source is above head whereas another client may have a lamp on his desk or be sitting by a window. Imagine how all of these can affect a client’s perception of the quality of match.

Measuring color
Color measurement can be carried out either by what is called a human colorist or by instrumental means. Using a human provides exceptional differentiation between colors but is limited in how this information can be transmitted to others and used as a control mechanism. Instruments sacrifice some color differentiation, but have the advantage in that they are reproducible every time. Instruments map onto a “color space” to provide the numbers or symbols for comparison and specification.

Hue is the basic color and is generally divided into a color wheel which ranges through 5 principals that include (red, yellow, green, blue, and purple) and all the variations in between. A simple color wheel is shown below. The location of a color around the wheel obviously defines the ‘hue’ of the color.

Lightness (brightness or value)
Lightness is the vertical axis and runs from light at the top to dark at the bottom. The location of a color on the lightness scale defines how light or dark the color will be.

Saturation (chroma)
The saturation of a color is how far away from the light axis it is – colors which are far away from the value axis are pure colors and those close to the value axis tend to be grayer. Saturation defines how pure a color is. Various color measurement systems have been developed in order to locate the 3D space. The very first system was the Munsell system developed by American artist Albert Munsell and this is known as “the rational way”. They use indicators such as 7.5PBYR 6/6. This indicates a purble blue hue but closer to purple with lightness of value 6 , a saturation of 6. This is a pure visual eval system.

The next is the CIE (International Commission on Illumination) of the Yxy color space, the L*a*b* color by CIELAB and the Hunter Lab color space. In the L*a*b* system which is typically used by 3D Laminate manufacturers to color control colors it uses the following:

L* defines the lightness/darkness of the color.
a* defines the greenness/redness of the color.
b* defines the yellowness/blueness of the color.
The combination of L*, a* and b* can be used to define the relationship between colors and as a quality control tool by most laminate manufacturers.Please note that “E” is the average of L, a and b so it is common to have the E number listed as well.

Color measuring instruments
The two most common types of machines for the measurement of color are the tristimulus colorimeter and the spectrophotometer. The tristimulus colorimeter is a machine that directly measures the sample color and uses red, blue, and green receptors. This is simliar to the human eye.

The major disadvantage with this type of machine is that the results are only meaningful under the specific illuminant used for the machine. Different colorants respond to different lights in different ways (a phenomenon known as metamerism as mentioned earlier in this report)

The spectrophotometer measures light across the whole of the visible spectrum to produce the full reflectance curve that can be processed to give the tristimulus values and chromaticity for any desired illumination. The full reflectance curve for various colors can be investigated to determine if metamerism will be present under varying illuminants.

The use of spectrophotometers requires knowledge of the type of machine being used and the detailed geometry of the machine – the various types available can detect or exclude texture and gloss levels and even take into account special effect finishes such as mica or flake colorants.

Measurement problems Metamerism: Color perception of many colorants is often affected by metamerism. This is where colors that may appear the same under one set of lighting conditions will appear different under a different set of lighting conditions. Typically in our industry metamorism takes place between fluorescent light sources and natural sun light since most manufacturers using the 3D Laminates do not have an International Standard Light box on premises.

Temperature: Color is often ‘thermochromic’ and most colors will change with the temperature at which the measurement is made.

Humidity: Color is often ‘hydrochromic’ and most colors will change with the humidity at which the measurement is made.

Methods of Coloring Plastics 3D Laminates
Plastics are typically colored by the following methods of printing, painting, pigments, internal colorants, dyes and surface colorants. For pratical purposes please note that the color of a 3D Laminate solid color is in the base calendered film whereas in a printed woodgrain the color is adjusted by the printing primarily using 1 to 5 print cylinders. This process is known as gravure printing where the print rollers (rotate) dip into an ink pan and rotate while applying the ink to the print layer. Printing can be done by direct to a print layer or via reverse printing to a clear transparent print layer. The average amount of printing cylinders is 3 and each cylinder must turn in register to one another in order to give the print clarity. The second way to adjust the color is through the base layer which can affect the darkness or lightless behind the print layer.

I hope that after reading this post you have picked up something new in regards to color, perception, procedure or that you have a better feeling for how humans interact with color. In some small way I hope that this article can influence how you sell color or how you may be more careful of conveying color to your client. Try to be observant of your customer’s light source, to the size of the sample and pay specific attention to the texture of the surfaces. I know that for me I utilize the basics of color knowledge every day. I just hope my X Chromosome isn’t defective ! ;-)

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