Why would a white shirt look like porridge?

The bleach used in laundry does not make your shirt really white, and LED lamps with extremely efficient power consumption of the future will reveal their true nature.

Many advertised detergents will "whiten" fabric fibers, but they will not actually do so. Instead, these detergents use a very smart optical effect to make your clothes look whiter when viewed under the eyes.

When white clothes become old, they will stain. Some detergents solve this problem by leaving on a fabric a chemical called the optical whitener (FWA) . FWA is capable of reflecting more blue light and thus creating the effect that your clothes remain as white as the day they were purchased. In fact, the yellow stain on the clothes is still retained, but the yellow eyes are more difficult to detect because they are affected by blue light.

This type of FWA helps create this "fake white" effect that is also used a lot in other areas. For example, people use FWA to whiten their teeth since the discovery of these compounds since 1929. FWA is also used to whiten paper, found in hair dyes and makeup creams. For example, yellow hair dye that contains FWA will be brighter, and dark area makeup creams under the eyes also use FWA.

White surfaces will reflect more light when there are FWA substances , and thus create the feeling that they are brighter, less yellow than they really are. The reason is that FWA will reflect UV ultraviolet light that the human eye cannot detect becomes blue light visible.

Currently, about 90 types of commercially produced chemical compounds can produce this effect, such as tetra-snfolnat triazole-stilbene . Most of these substances will become ineffective after a period of exposure to ultraviolet rays and oxygen, and some may cause side effects to a small group of users.

But LED models can affect this optical brightening "trick." The optical brightening process of FWA substances cannot take place in LED lights, simply because LEDs do not produce light in the ultraviolet range. The FWA participle will not be activated, and therefore blue light will not be created to cause optical effects.

While this problem is still not really worrying about chemistry, garment and aesthetics, but when LEDs become popular in the future, the substances FWA will become useless. LEDs have many advantages compared to conventional electric lights: they have a longer life span and a much lower electricity consumption. The market share of LED lights is expected to increase 12 times in the next decade; Las Vegas has now converted 40,000 street lights into LEDs.

In a study published last month on LEUKOS (a magazine of the North American Lighting Technology Association), a team of Penn State University researchers led by Dr. Kevin Houser conducted an experiment to Find out the ability to identify human white fabric in different light conditions.

In this experiment, the scientists asked 39 participants to rank "white levels" of fabric fibers, each containing a different amount of FWA. Penn State's research shows that LEDs will reduce FWA's "whiter" effect .

At the same time, the research team also showed that high-light LEDs in the blue strip will also help the fabric look whiter than usual - just like the effect of FWA. This effect will occur on all fabrics, regardless of whether they are removed with FWA.

Therefore, "responsibility" for whitening clothes will no longer belong to chemical companies. Instead, they belong to lamp manufacturers: they will have to increase the intensity of blue light on their LEDs. However, if they do this, they will also make all other white materials (tables, cabinets, appliances, etc.) whiter. That is not the expected result in all cases.

Penn State also thinks that manufacturers can add ultraviolet rays to LED lights, so that people can continue to "whiten" clothes like before without worrying about affecting types. other materials.