Many of us today were born during a time when modern laundering techniques were already available. Have you ever asked your grandparents how they maintained their clothes white as fresh before the arrival of the washing machine and oxygen bleach?

For hundreds of years, the sun was every household’s natural bleach to remove stains from clothes. Locals in the Philippines call this kulá, or sun bleach, and involves wetting and soaping the soiled item and spreading it out evenly under the sun. This technique works best for sheets and white soiled items, while one must exercise caution when sun-bleaching colored clothes and delicates to avoid fading and deteriorating their physical properties.

Photo shows women doing laundry during the colonial period in the Philippines. Colorized image is courtesy of Kinulayang Kasaysayan (

When you hear your grandparents command, “Ikula mo na ang mga damit,” they call upon the unique ability of the sun to break down molecular bonds of stains that effectively remove dirt. The sun does this through ultraviolet light (UV). UV is a powerful form of electromagnetic radiation with wavelengths from 10 nm to 380 nm, stronger than visible light but weaker than X-ray.

When UV light hits a material, it triggers a chemical reaction. For your body, the skin reacts to shield itself from UV, thus the suntan. For ordinary materials dried out in the sun, UV affects chromophores, thereby causing photodegradation, or the fading of colors. This reaction is simply perfect for white clothes and linen. UV breaks down the chemical bonds of stains, causing them to fade. In addition, UV also potentially kills microorganisms.

Many agree that 2 to 3 hours is the ideal period for sun-bleaching. To achieve a whiter fabric, this could be extended by exposing the linen the next day. However, remember that UV light’s nature is to break down chemical bonds. Long exposure eventually causes damage to the fabric.

Today, you rarely see this practice around, although one may still find this done in provincial areas. With the fast-paced nature of the city, people have shifted their time from doing housework, like laundry, to other activities. The rise of the washing machine and powerful detergents and bleaching agents have replaced traditional ways.

Modern Techniques

Our modern bleach (such as sodium hypochlorite) makes use of the process called redox reaction. Bleach breaks the bonds of stains by releasing oxygen or chlorine when it comes into contact with water. Chlorine produces hydrochloric acid and atomic oxygen. The oxygen chemically reacts with the chromophores and changes the physical color of the stain. 

To make this process more powerful, hot water is used. Hot water has more kinetic energy than cold water, which more efficiently activates the properties of bleaches – especially chlorine-based ones.

In addition, we now have optical brighteners, also called fluorescent whitening agents or photo bleach. Used in laundry detergents, sour, and fabric conditions, optical brighteners create an optical illusion of sparkling whiteness by enhancing blue light and minimizing yellow light.

Brighteners are already added on clothes in the manufacturing stage, but repeated washing with detergents degrade the original brighteners. Thus, while optical brighteners (on detergents, fab con, and sour) do not help clean clothes, they make clothes appear new, clean, and sparkling white (or snappy for colored items).

Laundry is an art and science that our ancestors have long practiced (since the Roman times). As we tackle the science of laundry, we also look back at the history of humanity making our lives better through technology.

Read Next: The Chemistry of Laundry

Event Alert: If you want to learn more about the science and business of laundry, Is It Clean? is organizing the 3rd Laundry Masterclass on October 9, 2-5pm (Manila time). Register here today

Image credit: The featured image is the work of Max Liebermann called “The Bleaching Ground” (1882). The image is licensed under Wikimedia Commons