A paint mixer matches paint almost exactly to the color that you want. Whether you use a paint card sample or bring an item from a room, paint is mixed to match. Some mixers can only go by the sample cards on display in the hardware store, and cannot take other types of color samples, but there are usually enough color samples to make a close approximation. Before this invention, basic colors were the norm and specialty paints had to be mixed by a professional with tints.
A spectrophotometer deciphers the colors and picks the one needed. A tungsten light bulb or LED light is used as the light source. White light is made up of all colors combined. This is seen when the light is refracted by a prism and causes a rainbow to be cast. A spectrophotometer works in the same way, breaking up the light into all the colors, so that the system is as accurate as possible when it analyzes the color.
Inside the spectrophotometer are interference filters. The color sample is processed through the filter and colors that do not match are reflected off of them. This creates an accurate reading of the color. The color then goes through the filters and is collected in the fiber optics to be sent to the photo diode. The diode transfers the reading into a signal that is read by the computer, which processes the correct amount of tint to be added to the paint. The number of tints depends on the brand and type of spectrophotometer being used. Some hold 12 tints, while others hold as many as 16. Tints are held in cylinders within the machine, and work like syringes, pressing tint through tubing and into the dispenser opening. The machine pushes the tints needed out of their cylinders and pours them out of the opening into the paint can waiting below.
After the tint is added, the lid is placed on the can, and the paint is placed in a mixer. Metal clamps hold the can in place, and the machine shakes the can extremely fast for several minutes. Afterward, the person on the paint counter opens the can and checks to make sure the paint is mixed thoroughly.