What is color and how do we see it?

When we describe an object one of the first things mentioned is its color. To see color we need light. Light travels in wavelengths called nanometers and each wavelength is a color. When light is shone into a prism we can see the individual wavelengths as color. When an object is exposed to light, it absorbs some of these wavelengths and reflects others. What we see as color are are the reflected wavelengths.

Dispersion of white light diagram

What is the best way to read or measure color?

It has been stated that our eyes are the best method for seeing and interpreting color however, many things can influence color vision. The surface, or emboss can change how we see the same color, lighting, and even certain medications can cause our eyes to interpret the same color differently. So what is the solution?

A method that controls the type of light, the angle of light, and is capable of measuring the absorption and reflection of light, with the means of storing all of this information. In other words, eliminate the potential for outside influences and maintain constant parameters.

A spectrophotometer can do all of this.

 

Visible light diagram

Spectrophotometers and how they work.

Spectrophotometers use a lamp for the light source. A beam of light strikes a diffraction grating, which works like a prism and separates the light into its individual wavelengths. The grating rotates so that only a specific wave length of light reaches the exit slit. Then the light interacts with the sample. A detector measures the samples transmittance and absorbance of the sample. Transmittance is the amount of light that passes through the sample reaching the detector. Absorbance is the measurement of light that is absorbed by the sample. The detector senses the light transmitted through the sample and converts this information to a digital display.

 

Spectrophotometer software image

How to Maintain Color Consistency

To maintain lot to lot consistency, first a standard and specification must be developed and stored into the spectrophotometer. Typically, a standard is established based on a control sample from your customer. The control sample is read by the spectrophotometer and the data results are stored in the database. This data is now available at any time and remains constant. The next step is to establish an acceptable range that the color can fall within and still be “on color”.

The best and possibly most important action to take to ensure color consistency is to establish color specifications on the raw materials. Confirm that raw material suppliers can meet the required specifications. Then develop evaluation tests for incoming raw materials.

Check your production! Schedule color evaluations throughout the production process to keep the color within specification.

Color is great until it is “off” and by monitoring materials and data your color will be “on” more often than not.

About the Author

Angie Schlabach Headshot

Angie Schlabach is Snyder Manufacturing’s Research & Development Supervisor/Colorist.