Do You Know Why Toilets Must Be White?

[Asia Economy Reporter Jin-kyung Lee] Have you ever seen a purple toilet? Can't imagine it? Most of the items we use are often associated with specific unique colors. Toilets are white, basketballs are orange, for example. Since when and why have certain colors become commonly used for each item? Let's take a look at the stories and backgrounds behind the colors of various objects.

1. Why are most toilets white?

Toilets have been white since their initial development to make it easier to check health. By looking at the toilet after using it, one can check if there is blood mixed in the urine or if the condition and color of the stool are normal, thus monitoring health. Additionally, white toilets have economic advantages in terms of pigment and processing costs compared to colored toilets. Furthermore, there is a perception that bathrooms should be clean, so white, symbolizing cleanliness, is used.

2. Why are many pencils overseas yellow?

When you go to a stationery store, you can see many yellow pencils. Why is that? In the 19th century, American pencil manufacturers, from the world's largest pencil industry country, wanted to highlight that their pencils used high-quality Chinese graphite. They painted the pencils yellow, a color symbolizing Chinese royalty at the time, to give a luxurious feel and to make consumers associate the pencils with China. Even now, about 75% of pencils sold in the U.S. are yellow.

3. Why are children's buses yellow?

The reason children's buses are yellow is safety. Yellow attracts people's attention faster than other surrounding colors. In fact, even in dark or foggy environments, our eyes detect yellow first. Therefore, to easily catch drivers' attention, children's vehicles, road warning signs, and center lines are yellow. (*In 1939, yellow was designated as the color to protect children safely. In Korea, this has been implemented since 1997.)

4. Why are most airplanes white?

Many airplanes have a white base color. Why? Cracks, scratches, corrosion, and other signs of abnormalities often appear as dark colors, so white makes it easier to spot these issues. Also, in case of unexpected crashes or night flight accidents, white makes the aircraft more visible and easier to identify from afar. When flying above clouds, airplanes receive a lot of sunlight; white reflects UV rays more effectively than other colors, keeping the interior cooler and preventing surface color changes caused by sunlight. There is also an economic benefit: among special paints used on airplanes, white is the cheapest. Airlines can easily display and identify their logos on white surfaces.

5. Why is tunnel lighting yellow?

Although new tunnels with white LED lighting are being built, most tunnels still maintain yellow lighting. Why? Tunnel interiors are dark and visibility is reduced due to smoke and exhaust gases. To secure visibility and prevent accidents, yellow lighting with a long wavelength is used. The lighting used in tunnels is sodium lamps, which appear yellow but actually emit wavelengths that the human eye perceives as green. Sodium lamps have the advantage of attracting fewer insects but consume more power and have higher maintenance costs. Therefore, tunnels with LED lighting, which offer better visibility and higher luminous efficiency, are increasing.

6. Why do different types of alcohol bottles have different colors?

Makgeolli undergoes secondary fermentation during distribution, producing gas that expands the volume inside the bottle. If a glass bottle expands, it could burst, so Makgeolli is stored in safer white PET bottles.

Beer is a fermented beverage made by sprouting barley malt, filtering the juice, adding hops, and fermenting with yeast. Since hops can change the taste when exposed to sunlight, beer is stored in brown bottles that block ultraviolet rays.

Soju is obtained by heating fermented liquor and cooling the collected vapor. Therefore, it is less affected by sunlight and is stored in green bottles that give a clean image and feel.

7. Why are baseball players' eye patches black?

Our facial surface is uneven, but due to sebum and sweat during games, the reflectivity of light increases, causing a phenomenon similar to reflection on a smooth surface. This can cause severe glare for players, so baseball players attach eye patches under their eyes. Most are black because black absorbs all light and does not reflect sunlight. Thus, the eye patch absorbs light, reducing glare and allowing players to concentrate on the game.

8. Why is the basketball orange?

The basketball is orange to ensure visibility. Unlike other sports, basketball is played in a confined space with many players moving quickly. Using a white ball, although visible, can reflect light and cause eye fatigue for players. Therefore, an orange ball, similar in color to the brown court floor, is used to reduce eye fatigue and increase concentration.

9. Why are tennis balls fluorescent yellow?

Originally, tennis balls were white or black. The color changed to the current one in 1972. Why? The reason was the advent of color TV. In the late 1960s, Wimbledon was broadcast in color TV for the first time. The white tennis ball blended with the white lines on the court, causing confusion for TV cameras. Also, while white balls were easy to see on black-and-white TVs, they were hard to see on color TVs. Eventually, the International Tennis Federation decided to change the ball color and, after comparing various colors, chose fluorescent yellow, officially adopted in 1986.

10. Why are warships mostly gray?

Warships seen in news or photos are mostly gray. Why? When fog forms near the horizon at sea, gray warships are hard to detect. But did you know the bottom of the ship submerged in water is red? This is because aquatic organisms like shellfish attaching to the hull increase resistance, leading to higher fuel consumption and slower navigation. To prevent this, anti-fouling paint is applied. One component of this paint, copper(I) oxide, is red, giving the paint its red color.