What Makes #2 Pencils So Special?

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Most of us pick up pencils—and lose them—without giving them a second thought. Pencils are a bit more interesting than you might, think, though. Here are a few not-so-frequently asked questions about everyone's second-favorite writing implements, including the story of a time when pencil sharpeners were illegal.

WHAT MAKES #2 PENCILS SO SPECIAL?

When it comes to pencils, #2s are actually the absolute middle of the road. While we number our various grades of pencils in the U.S., the rest of the world uses a system of numbers and letters to describe how hard and how black a pencil's lead is. An American #2 pencil (roughly) corresponds to an HB pencil on the rest of the world's scale. The lead is not too dark and not too light, and it's not too hard or too soft.

Pencils numbered higher than 2 have harder leads and are often used by engineers, architects, and draftsmen because of their harder points. The underlying logic here is that the harder point gives the user greater control of the lead. You'll find softer leads in pencils numbered below 2, which are popular with artists because they can help create a wider spectrum of tones than one would achieve by sticking solely to a #2 pencil.

ACK! I USED A #3 PENCIL ON THE SAT! IS MY LIFE OVER?

A student takes a test with a pencil
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No ... but you're probably destined for a life of hard labor rather than college. No, not really. It's hard to get a straight answer on this question, but there are quite a few reports from people online who messed up by using the wrong grade of pencil and still did just fine on their SATs. The general consensus seems to be that the SAT's scanners will read a #3 pencil's mark just the same as it would read one from a #2 pencil. Some people do feel, however, that the harder lead in a #3 pencil makes erasing tougher and ups the chances that a stray smudge or incompletely erased mark will be read by the scanner and end up hurting your score. So it's probably best to err on the safe side and double-check your pencil type before heading into the exam.

IF THE REST OF THE WORLD USES A SYSTEM OF NUMBERS AND LETTERS TO GRADE PENCILS, WHY DO WE USE JUST NUMBERS?

Thank Henry David Thoreau and his old man. When graphite was discovered in New Hampshire during the 1820s, John Thoreau and his brother-in-law Charles Dunbar built their own pencil factory. The only problem was that New Hampshire graphite was pretty crummy; it smeared and made for pretty poor pencils.

Enter a young Henry David Thoreau. Before he wrote about civil disobedience and spent his time at Walden Pond, he worked at the family pencil company. Thoreau perfected a process of using clay as a binder to make the soft, loose graphite hard and suitable for pencils. Suddenly the New England graphite could be used to make a pencil that didn't leave giant smears, and the Thoreaus' business took off. By the middle of the 19th century, the Thoreaus were selling pencils with varying graphite hardness, which they numbered one through four.

IF THE CENTER OF THE PENCIL HAS BEEN MADE OF GRAPHITE FOR SO LONG, WHY DO WE CALL IT "LEAD"?

Photo of the tip of a pencil
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Blame shoddy 16th century chemistry for this one. When a giant graphite deposit was found in England during the 16th century, it eventually found a use as a writing implement. However, early chemists weren't exactly sure what the useful gray substance actually was. They assumed it was some sort of lead, and the term "pencil lead" came into use—even though there wasn't any lead involved.

WHY ARE PENCILS PAINTED YELLOW?

According to most stories, our pencils are yellow as a result of a clever marketing gimmick. In 1889, the Hardtmuth company of Austria introduced a new line of fancy pencils at the World's Fair in Paris. The pencils were named Koh-i-Noor after a famed Indian diamond, and they contained the world's finest graphite from the Far East. They were also painted yellow, which was unusual at the time.

Some historians claim that the Austrian company painted their pencils yellow as a subtle nod to the yellow on the flag of Austria-Hungary. Others claim the yellow was an even subtler nod to the Far Eastern graphite in the pencils; the color yellow is associated with royalty in China. In either case, the new yellow pencils were a hit, and soon other companies began painting their own wares yellow in an attempt to swipe some of Hardtmuth's business.

DOES THE LITTLE METAL BAND THAT HOLDS THE ERASER ON THE PENCIL HAVE A NAME?

A pencil eraser
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It sure does. It's called a ferrule, a combination of the Latin words viriola ("small bracelet") and ferrum ("iron").

HAVE PENCIL ERASERS GIVEN US ANY COMMON WORDS?

You bet. According to records from the 18th century, the elastic substance from tropical plants got its name thanks to its common use of being rubbed over pencil marks to erase them. Since using this substance as an eraser required a lot of rubbing, people began calling it rubber. Another name for rubber from the same era that didn't catch on quite as well was lead-eater

WHEN WAS IT ILLEGAL TO OWN A PENCIL SHARPENER?

If you owned a pencil sharpener in early 20th century England, you had a hot little piece of contraband. At the time, the supply of the red cedar that had historically been used in pencils was getting perilously low, so the government briefly outlawed pencil sharpeners in order to limit waste from overzealous sharpening. Eventually the mechanical pencil and the discovery of incense-cedar's usefulness in making pencils solved this problem, and pencil sharpeners became street legal once again. Phew!

Why Does Humidity Make Us Feel Hotter?

Tomwang112/iStock via Getty Images
Tomwang112/iStock via Getty Images

With temperatures spiking around the country, we thought it might be a good time to answer some questions about the heat index—and why humidity makes us feel hotter.

Why does humidity make us feel hotter?

To answer that question, we need to talk about getting sweaty.

As you probably remember from your high school biology class, one of the ways our bodies cool themselves is by sweating. The sweat then evaporates from our skin, and it carries heat away from the body as it leaves.

Humidity throws a wrench in that system of evaporative cooling, though. As relative humidity increases, the evaporation of sweat from our skin slows down. Instead, the sweat just drips off of us, which leaves us with all of the stinkiness and none of the cooling effect. Thus, when the humidity spikes, our bodies effectively lose a key tool that could normally be used to cool us down.

What's relative about relative humidity?

We all know that humidity refers to the amount of water contained in the air. However, as the air’s temperature changes, so does the amount of water the air can hold. (Air can hold more water vapor as the temperature heats up.) Relative humidity compares the actual humidity to the maximum amount of water vapor the air can hold at any given temperature.

Whose idea was the heat index?

While the notion of humidity making days feel warmer is painfully apparent to anyone who has ever been outside on a soupy day, our current system owes a big debt to Robert G. Steadman, an academic textile researcher. In a 1979 research paper called, “An Assessment of Sultriness, Parts I and II,” Steadman laid out the basic factors that would affect how hot a person felt under a given set of conditions, and meteorologists soon used his work to derive a simplified formula for calculating heat index.

The formula is long and cumbersome, but luckily it can be transformed into easy-to-read charts. Today your local meteorologist just needs to know the air temperature and the relative humidity, and the chart will tell him or her the rest.

Is the heat index calculation the same for everyone?

Not quite, but it’s close. Steadman’s original research was founded on the idea of a “typical” person who was outdoors under a very precise set of conditions. Specifically, Steadman’s everyman was 5’7” tall, weighed 147 pounds, wore long pants and a short-sleeved shirt, and was walking at just over three miles per hour into a slight breeze in the shade. Any deviations from these conditions will affect how the heat/humidity combo feels to a certain person.

What difference does being in the shade make?

Quite a big one. All of the National Weather Service’s charts for calculating the heat index make the reasonable assumption that folks will look for shade when it’s oppressively hot and muggy out. Direct sunlight can add up to 15 degrees to the calculated heat index.

How does wind affect how dangerous the heat is?

Normally, when we think of wind on a hot day, we think of a nice, cooling breeze. That’s the normal state of affairs, but when the weather is really, really hot—think high-90s hot—a dry wind actually heats us up. When it’s that hot out, wind actually draws sweat away from our bodies before it can evaporate to help cool us down. Thanks to this effect, what might have been a cool breeze acts more like a convection oven.

When should I start worrying about high heat index readings?

The National Weather Service has a handy four-tiered system to tell you how dire the heat situation is. At the most severe level, when the heat index is over 130, that's classified as "Extreme Danger" and the risk of heat stroke is highly likely with continued exposure. Things get less scary as you move down the ladder, but even on "Danger" days, when the heat index ranges from 105 to 130, you probably don’t want to be outside. According to the service, that’s when prolonged exposure and/or physical activity make sunstroke, heat cramps, and heat exhaustion likely, while heat stroke is possible.

Have you got a Big Question you'd like us to answer? If so, let us know by emailing us at bigquestions@mentalfloss.com.

This article has been updated for 2019.

Is the Heat Index Real?

MarianVejcik/iStock via Getty Images
MarianVejcik/iStock via Getty Images

Complaining about the humidity is a mainstay of small talk. “It’s not the heat that gets you, it’s the humidity” is a common refrain around the South, just as “it’s a dry heat” is a go-to line in the desert Southwest. The clichés aren’t wrong on this one—a hot and humid day can have a dramatic effect on both your comfort and your health. We can measure this very real impact on your body using the heat index. 

The heat index is the temperature it feels like to your body when you factor in both the actual air temperature and the amount of moisture in the air. If the heat index is 103°F, that means that the combination of heat and humidity has a similar physical impact on your body as it would if the actual air temperature were 103°F. Even though it’s tempting to think of the heat index as an exaggerated temperature that only exists to make the heat sound worse than it really is, scientists came up with the measurements after decades of medical and meteorological research devoted to studying the impact of heat and humidity on the human body. It’s the real deal.

The dew point is an important component of the heat index. The dew point is the temperature at which the air would reach 100 percent relative humidity, or become fully saturated with moisture like on a foggy morning. Since cooler air can’t hold as much moisture as warmer air, lower dew points reflect lower moisture levels and higher dew points indicate higher moisture levels. Dew points below 60°F are comfortable, while readings reaching 70°F and even 80°F range from muggy to downright oppressive.

Measuring humidity on a hot day is important because moisture is how your body naturally cools itself off. Your sweat cools the surface of your skin through a process known as evaporative cooling. If the air is packed with moisture, it takes longer for your sweat to evaporate than it would in more normal conditions, preventing you from cooling off efficiently. The inability to lower your body temperature when it’s hot can quickly lead to medical emergencies like heat exhaustion or heat stroke, which is why the heat index is such an important measurement to pay attention to during the summer months.

The heat index is generally considered “dangerous” once the value climbs above 105°F, and your risk of falling ill increases the higher the heat index climbs.

Dry climates can have the opposite effect on your body, with the distinct lack of moisture in the air making it feel cooler to your body than it really is. Summers get oppressively hot in places like Arizona and Iraq, but the heat doesn’t affect residents as severely because the air is extremely dry. Dew points in desert regions can hover at or below 32°F even when the air temperature is well above 100°F, which is about as dry as it can get in the natural world.  

In 2016, a city in Kuwait measured the all-time highest confirmed temperature ever recorded in the eastern hemisphere, where temperatures climbed to a sweltering 129°F during the day on July 21, 2016. The dew point there at the same time was nearly 100 degrees cooler, leading to a heat index of just 110°F, much lower than the actual air temperature. That’s not necessarily a good thing. Extreme heat combined with extreme aridity can make your sweat evaporate too efficiently, quickly dehydrating you and potentially leading to medical emergencies similar to those you would experience in a much more humid region of the world. 

Have you got a Big Question you'd like us to answer? If so, let us know by emailing us at bigquestions@mentalfloss.com.

This story has been updated for 2019.

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