Why do we wear light colors in summer?

Come on, I'm sure you've already asked yourself this question: where does our habit of taking colorful shirts out of the closet at the first rays of sunshine come from?

If the origin of this custom is not easy to determine, I can still take you on a tour of the few reasons which, combined together, give us a global explanation.

In this article, we're going to play with a glass prism, flip through a few pages of history, and get inside your head. Are you ready ?

Reason #1: Because light colors often feel less warm

This is a first reason often mentioned, which results in a systematic thought pattern:

“Light color = less hot in summer”

With a champion in the field (unless the latter is synthetic, of course!) the white t-shirt.

Our common sense has therefore always instinctively led us to wear light-colored clothing when it is hot in summer. All this, keeping in mind the equally automatic reciprocal for us:

“Dark color = warm in summer”

With public enemies at the top of the podium in summer: the black t-shirt (photo: white essentials).

On a large scale, it is therefore quite logical that this idea, as stubborn as a wine stain on your white shirt, played its role in the invasion of light colors in summer.

But where does this information come from? Is it systematically true?

Well it comes to us from the laws of physics. But we will see that the diagram is not so simple, and that nothing is all black or all white.

Colors and warmth: why are they linked?

What is a color?

To answer this question, we must first define what light is.

Light, particularly that of the sun, is electromagnetic radiation which is broken down into a spectrum of colors.

Of the entire spectrum, a central part is called the "visible spectrum". A portion of the latter is reflected on objects to allow us to distinguish their color.

The rest of the spectrum not visible to the naked eye is made up of infrared and ultraviolet rays. These can also be reflected on an object, but without influencing what we see.

This is how sunlight breaks down. (Photo credit: expertoptic.com).

Of course, you don't literally see a rainbow starting from the sun. But if you decompose the light through a glass prism, it is this “visible” part that you will distinguish.

This legendary cover from the Pink Floyd group will be able to explain it to you better than me: direct a ray of white light onto a glass prism, and it will "disperse" into several colors that compose it. (Album: Dark side of the moon).

These colors correspond to different wavelengths, as you can see here:

Each color that makes up light is a wave that will have a certain length, measured in nanometers.

An object illuminated with light will therefore receive the entire spectrum and:

• Will absorb a certain part
• Will reflect the rest

The reflected part is therefore the part that our eye will perceive. The waves, and therefore the colors reflected by the object, will together give rise to the color that our eye will perceive on this object.

For example, if a t-shirt reflects a red and green part of the visible spectrum, it will be yellow to our eyes.

And if we see it yellow, it is because the sensors located in our retinas will interpret it as follows:

1. Our eye perceives waves of different lengths ,
2. Our sensors, based on the three primary colors, interpret these waves,
3. The information is sent to our brain, which will somehow interpret the meeting of these primary colors.

When we see white clothing, it is in fact because it reflects the entire visible spectrum to us. .

Conversely, a black object decides to absorb the entire visible spectrum, leaving nothing visible other than an absence of color.

In principle, the lighter a color is, the more it reflects a large part of the visible spectrum. Conversely, the darker a color, the more it will absorb.

All right. But how will a body choose which wavelengths to reflect or absorb?

He could have flipped a coin, but he prefers to rely on its atomic and molecular properties, the structure of its surface, and the angles with which light hits it.

This is why you can barely distinguish the color of objects in a dark environment: they do not have enough visible spectrum to reflect. The rails at the bottom only have the red part of the spectrum to reflect back to us. (Photo credit: Andre Benz - Unsplash).

Now that you know more about light and what color is, let's look at how it relates to heat.

What is heat?

Heat corresponds to the movement of the molecules that constitute a body: the more they move, the hotter the body in question will be.

And this heat can be transferred from one body to another in three ways:

• By conduction, via the friction of molecules. The atoms will move from a cold region to a warmer region when the two bodies come into contact. Example: when you leave an object on a hot plate, it will heat up in turn.
• By convection, when within a fluid in contact with a solid, molecules move from hot regions to cold regions. Example: we’ll come back to this later.
• By radiation, when the body emits more or less intense energy radiation depending on its temperature. This energy can be light. Example: the sun.

It is this third case that will interest us here.

Because a picture is worth a thousand words: here is a situation that well represents the three modes of heat transfer. (photo credit: jeretiens.net).

What is the relationship between color and heat?

When an object absorbs part of the spectrum that constitutes light, it is not just absorbing waves. It also absorbs the energy associated with it.

We are therefore in the middle of a process of transfer by radiation: the electromagnetic waves of the absorbed spectrum agitate the molecules and generate heat.

The more waves an object absorbs, the more energy it will store and heat up. However, as we have seen, dark colors are quite selfish, since they keep a greater part of these waves for themselves.

For example, a black object will absorb approximately 90% of the energy arriving at it from the sun.

And once this energy has been absorbed, it is through conduction that your dark clothing will release this heat partly onto you.

According to these principles, dark-colored clothing is actually supposed to keep you warmer in summer via its absorption of light. With a difference that can exceed 6 degrees on the surface. .

This is what the sun sees when you leave the house in a black t-shirt. (Photo: Pixabay).

But as I said just before, the truth is not that simple.

A rule far from absolute

In fact, everything will depend on the climatic conditions.

Firstly, our body also emits heat by radiation, heat which will be:

• Absorbed in a black t-shirt
• Reflected back to ourselves by a white t-shirt

Enough to moderate the temperature difference explained above.

Faced with summer heat, what will determine the real winner between light and dark will mainly be the wind.

If it is strong enough, the heat absorbed by your black clothing from your body and exterior light will be properly evacuated. Making the dark garment more effective than its light counterpart.

Conversely, without wind, the heat that your dark clothing will propagate by radiation or conduction will not be evacuated: it will remain on you. You will therefore be heated by the latter, and white or light clothing would have been more effective in this case. The latter reflects the waves instead of absorbing them. So this is the basic rule that will apply here.

So, to dress in summer, I check the wind speed in the morning and advise accordingly?

I can already see some coming from afar with their anenometer. (Photo credit: Météoshopping).

No.

Of course, these comparisons are made with equal clothing. And above all, the color of the clothing has significantly less influence than the other factors:

• the nature of the fiber
• weaving
• the cut of the garment

The Bedouins: the exception that proves the rule

A black dress in more than 30 degrees, or how to question an entire scientific reasoning in a single photo (photo credit: Getty).

The case of the Bedouins in black robes is an excellent counter-example to qualify the "dark color = warmth" shortcut. It has also aroused the curiosity of many researchers who have looked into it. The most famous study being that carried out by Israeli researchers Amiram Shkolnik, C. Richard Taylor, Virginia Finch and Arieh Borut.

We compare, under equal climatic conditions, the temperatures observed in the case of wearing a white dress and a black dress.

Although the temperature of the black coat rose to 47 degrees compared to 41 for the white coat, that of the body remained at 33 degrees in both cases. So what is their secret?

Remember: I told you above that I will return to an example of heat transfer by convection. Here we are.

In fact, the air heated between the black dress and the lower layer of clothing becomes less dense than the surrounding air and escapes through the top, creating a draft of air under the dress. The latter will bring in cooler air, and will therefore ensure natural ventilation before the heat reaches the body.

Under sunlight, the energy gain (and therefore heat) of the black dress was approximately 200 watts higher than that of the white dress ("radiation gain"). However, the loss of energy via convection (“convection loss”) is twice as effective for the black dress.

This convection phenomenon is also at the origin of the effectiveness of Bedouin black tents. (photo credit: Wikipedia).

Reason #2: Story comes into play

White: king of summer in America

The general preference for light colors in summer also has some historical origins. More particularly in the case of white clothing. And to be original: we find these origins in the United States.

At the beginning of the 20th century, white clothes were not the most practical to wear in the city.

And to give you an idea of ​​why, I'll let you imagine the state of cleanliness of a city in full industrialization, where horses are still used as a means of transport:

• abundant use of coal,
• horse droppings at every road crossing,
• dust and dirt of all kinds,

In winter and mid-season, sprinkle everything with a little rain and wind. You will quickly understand the lack of motivation of the inhabitants to take care of light-colored clothes, on which any stain would be easily seen. White being an extreme case, it was quickly banned during the year.

As Charlie Scheips, author of the book American Fashion, says in this Time article, this was the case for journalists, for example. Sources of significant influence at the time, the latter put aside their white outfits in the fall.

I guess you wouldn't go for a ride on that muddy road in white pants? (Photo: Main road in Goulcester, Massachusetts - 1900, Wikipedia).

So, the great opportunity to treat yourself by putting on a white outfit was when you left the city in summer to go to your country house, so clean and well maintained. Of course, this was the case for the wealthiest populations, who had the necessary means to be able to stop working in the summer, go on vacation, and have a second home.

Then, once Labor Day past, we put on our dark clothes to tackle the formality of the working world.

This is how white clothing has become a symbol of summer, relaxation, but also of relative wealth.

If we see so much white in summer today, it is partly due to these ladies and gentlemen. (Photo: Tysto.com).

Although the cleanliness of cities subsequently made great progress, this symbolism of white clothing has persisted. It has even become a factor of social demarcation, with the wealthy classes relying on this tradition to defend their position in society.

This type of clothing rule allowed them to assert their legitimacy against the “nouveau riche” of the time. Making this custom a real barrier to entry, as Valerie Steele, director of the Fashion Institute of Technology museum, explains in the Time article.

For Coco Chanel, white is all the time

From the 1920s, the designer went against the codes by wearing white during the year. She will make it a trend that will soon moderate the “dictatorship” of dark clothing in winter. Not without resistance from wealthy populations.

For the great seamstress, white clothing had no timetable. (Photo: Horst P. Horst/Conde Nast via Getty Images)

Nevertheless, we can still see the traces of the social anchoring of white in summer. Accompanied by the general thought on the relationship of colors to heat, this historical origin is therefore far from being negligible.

Reason #03: our psychological perception of colors

A color is also a language: it represents a symbol that intrigues the historian as well as the sociologist, the psychologist... or the fashion designer.

Each civilization has built its own culture around colors, accumulating a set of notions to which they refer.

The meaning of colors is also widely used in the fields of communication and advertising: brands do not choose their logo at random. (Photo credit: creanico.fr).

Let's take the example of black.

Black was the color worn by ecclesiastics during the Protestant Reformation. During the 19th century, people representing authority also wore black: firefighter, clergy, etc...

Result ? In the eyes of Western populations, black was therefore linked to respect, formality, and austerity. We therefore find here the formalism given to dark colors.

Later, notably with the arrival of Coco Chanel , black clothing will be associated with luxury, elegance and chic.

Do you see the idea? (Audrey Hepburn in a Givenchy dress, Breakfast at Tiffany's - 1961).

The palette of bright colors that we may wear in the hot season are therefore not without connotation either:

• After referring to the notions of gambling, luck, and negative superstition , green was associated to nature, and to life.
• Yellow is linked to flowers and spring rebirth
• Orange can bring to mind emotion, optimism or even the sun
• Blue is identified with the sky, the ocean, and escape

Nature, flowers, sun, ocean, escape, optimism... so many notions that we easily associate with summer or vacation.

Little exercise: what does this shirt make you think of? Have you often come across these kinds of colors and patterns in the middle of winter? (Photo: Black Flag).

In Western culture, it is therefore often by consistency with the semiological universe of light or bright colors that we wear these in a summer setting.

An extreme example, from the eccentricities of haute couture, where we find the total: greenery, flowers and the sun. (Photo: still the Dior spring/summer show).

Now you know why your pale pink shirts blend in better when they're in the sun .