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How Does Scratch and Sniff Work?

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Scratch and sniff was born of the noble endeavor of making copies. In the dark ages before word processors, inkjet printers, and the Xerox machine, copies of documents were made by placing carbon paper between the sheet you were typing on and the sheet that would become the copy. In the early 1960s, an organic chemist at 3M named Gale Matson developed a way to make ink copies without carbon paper, using a process called microencapsulation.

The Matson process uses two sheets of paper "“ one for the original document and one for the copy "“ on top of one another. The top sheet of paper is coated with microcapsules of colorless ink. When someone writes or types on the paper, the capsules break and release their ink, which mixes with a developer chemical on the second sheet to create a copy.

Not wanting Matson's technology to be a one trick pony, 3M began to search for alternate uses for micro-encapsulation and found that it could be applied to scented oils as well as ink. Scratch 'N Sniff debuted in 1965 and is found in various forms, from stickers to pull-apart perfume sample strips and beyond.

How It Works

1. Scented oil is mixed with a solution of water and water-soluble (capable of being dissolved in water) polymer (3M uses polyoxymethylene urea) in a large vat called a reactor.

2. The mixture is blended at a high speed by a rotary blade. As the oil and polymer solution mix, the oil breaks into very small droplets. After about 12 hours of blending, the droplets are about 20 to 30 microns in size, invisible to the naked eye.

3. When the droplets are the right size, the blending is stopped and a chemical catalyst is added. The catalyst causes the molecular weight of the polymer to increase and become water insoluble. The polymer precipitates out of the water and forms a shell around, or encapsulates, each individual droplet of oil.

4. The reactor is stopped, and the microcapsules are collected and washed to remove any unreacted or unencapsulated materials.

5. The capsules are placed in a tank and mixed with a water base and an adhesive, forming a thick slurry.

6. The slurry is ready to be applied to paper, and there are four basic methods for doing this: silk-screening, web offset printing, flexo-graphic printing (this is what is used for scratch and sniff stickers) and extrusion (a fairly complex printing method used for making perfume and cologne sample strips).

Smelling the finished product is just like smelling anything else. When we scratch the surface of the paper, the microcapsules break and the scented oil travels to our nasal cavity, where the molecules are detected by the olfactory sensory neurons in the olfactory epithelium. A signal is sent to the brain, which translates it, and then we say, "Oooh, banana!"

Click & Sniff

We've come a long way since the birth of Scratch 'N Sniff, and now we don't need micro-encapsulation to smell exotic scents whenever we want. Heck, we don't even need to scratch. Here are some more recent developments in digital scent technology.

DigiScents Inc. in Oakland, California, created the iSmell scent synthesizer. You insert a scent cartridge into the iSmell, which is connected to a computer or video game console, and it releases the scent in short bursts at appropriate times, i.e. when you're playing a first person shooter and get into a firefight, you'll actually get whiffs of gunpowder as you fire rounds. Before you get too excited, PC World named the iSmell one of the 25 Worst Tech Products of All-Time.
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ScenTeck Technologies' Scratch-N-Sniff Pro software and System Scent Card replace the standard vibrating sound waves coming from computer speakers with unique vibrating tones that the brain recognizes not as a sound, but a scent.
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Unleashed, an album by Savannah, Georgia-based musician Zan, is the world's first scent-enabled CD. A gadget called a Scent-Dome plugged into your computer reads code embedded in the CD and releases different scents as the songs play.

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Big Questions
What's the Difference Between Vanilla and French Vanilla Ice Cream?
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iStock

While you’re browsing the ice cream aisle, you may find yourself wondering, “What’s so French about French vanilla?” The name may sound a little fancier than just plain ol’ “vanilla,” but it has nothing to do with the origin of the vanilla itself. (Vanilla is a tropical plant that grows near the equator.)

The difference comes down to eggs, as The Kitchn explains. You may have already noticed that French vanilla ice cream tends to have a slightly yellow coloring, while plain vanilla ice cream is more white. That’s because the base of French vanilla ice cream has egg yolks added to it.

The eggs give French vanilla ice cream both a smoother consistency and that subtle yellow color. The taste is a little richer and a little more complex than a regular vanilla, which is made with just milk and cream and is sometimes called “Philadelphia-style vanilla” ice cream.

In an interview with NPR’s All Things Considered in 2010—when Baskin-Robbins decided to eliminate French Vanilla from its ice cream lineup—ice cream industry consultant Bruce Tharp noted that French vanilla ice cream may date back to at least colonial times, when Thomas Jefferson and George Washington both used ice cream recipes that included egg yolks.

Jefferson likely acquired his taste for ice cream during the time he spent in France, and served it to his White House guests several times. His family’s ice cream recipe—which calls for six egg yolks per quart of cream—seems to have originated with his French butler.

But everyone already knew to trust the French with their dairy products, right?

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

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Big Questions
How Many Rings Does Saturn Have?
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NASA/JPL-Caltech/Space Science Institute

Of all the planets surrounded by rings, Saturn is the most famous. These planetary rings are massive enough that Galileo was able to see them using a simple telescope way back in 1610, though it wasn't until half a century later that another scientist was able to figure out what the "arms" Galileo saw actually were. NASA has since called them "the most recognized characteristic of any world in our solar system."

So how many rings does Saturn have, anyway? If you can see them from your backyard, there must be a lot, right?

Scientists don't know for sure exactly how many rings Saturn has. There are eight main, named ring groups that stretch across 175,000 miles, but there are far more than eight rings. These systems are named with letters of the alphabet, in order of their discovery. (Astronomers have known about ring groups A, B, and C since the 17th century, while others are newer discoveries. (The most recent was just discovered in 2009.)

The rings we can see in images of the planet—even high-resolution images—aren't single rings, per se, but are in fact comprised of thousands of smaller ringlets and can differ a lot in appearance, showing irregular ripples, kinks, and spokes. The chunky particles of ice that make up Saturn's rings vary in size from as small as a speck of dust to as large as a mountain.

While the gaps between Saturn's rings are small, the 26-mile-wide Keeler Gap is large enough to contain multiple moons, albeit very small ones. The largest ring system—the one discovered in 2009—starts 3.7 million miles away from Saturn itself and its material extends another 7.4 million miles out, though it's nearly invisible without the help of an infrared camera.

Researchers are still discovering new rings as well as new insights into the features of Saturn's already-known ring systems. In the early 1980s, NASA's Voyager missions took the first high-resolution images of Saturn and its rings, revealing previously unknown kinks in one of the narrower rings, known as the F ring. In 1997, NASA sent the Cassini orbiter to continue the space agency's study of the ringed planet, leading to the discovery of new rings, so faint that they remained unknown until Cassini's arrival in 2006. Before Cassini is sent to burn up in Saturn's atmosphere in September 2017, it's taking 22 dives through the space between the planet and its rings, bringing back new, up-close revelations about the ring system before the spacecraft dives to its death.

Though it's certainly possible to see Saturn's rings without any fancy equipment, using a low-end telescope at your house, that doesn't mean you always can. It depends on the way the planet is tilted; if you're looking at the rings edge-on, they may look like a flat line or, depending on the magnification, you might not be able to see them at all. However, 2017 happens to be a good year to see the sixth planet, so you're in luck.

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

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