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Why Is Laundry Detergent Blue?

September 1, 2020

Jennifer M. Woodson is a textile expert and consultant in the fashion industry.

Wash. Dry. Fold. Repeat. Every week you spend time doing laundry, but have you ever thought about what chemicals are working hard in the steel drum (that's your washer) to remove the grass stains from your kids' shorts and at the same time the color of your lucky football jersey? How about those beautiful white linens? What is keeping those white, fluffy towels from turning grey or yellow?

In 2018, Americans spent over $3 billion on laundry detergent -- yes, Tide is king in laundry detergent world and that may have something to do with the "cleaning power" you often hear referenced in Tide adverts. So what contributes to cleaning power?

Two of the most common detergent components are surfactants and optical brighteners. Surfactants are also referred to as wetting agents-- these chemicals reduce the surface tension of water to improve the wettability of the garments being laundered; simply stated, it helps the fabric get wet so the other other parts of the detergent can get to work removing stains. Surfactants also serve as emulsifiers-- they have an affinity for oil and dirt so during the wash cycle the surfactants will attach to the oil and dirt and hold on to it so that during the rinse cycle it is not redeposited on your garment.

Optical Brightening Agents (OBAs), also referred to as Fluorescent Whitening Agents (FWAs), are another component of laundry detergent and is why most laundry detergents are the color blue. In essence, a very light blue tint on a white piece of fabric will emit more visible light than that which shines on it, making it appear brighter. This is what keeps your garments from looking dingy gray or yellow after repeated washings. The concept of using blue to create the appearance of bright white has been around since at least the mid-1800s-- at that time, it was referred to as "Bluing".

Optical Brightener Under Normal Light (Left) and UV Light (Right)
Optical Brighteners are commonly used in the textile industry to produce fabrics that have bright whites and even bright colors (the colors of a dyed fabric will appear brighter and more vibrant if the fabric is first treated with an OBA).

The next time you do your laundry, check your detergent label to see if you recognize the Surfactants and Optical Brighteners that we reviewed today.