How Does Scratch and Sniff Work?

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 Do Morticians Do With the Blood They Take Out of Dead Bodies?
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Zoe-Anne Barcellos:

The blood goes down the sink drain, into the sewer system.

I am not a mortician, but I work for a medical examiner/coroner. During an autopsy, most blood is drained from the decedent. This is not on purpose, but a result of gravity. Later a mortician may or may not embalm, depending on the wishes of the family.

Autopsies are done on a table that has a drain at one end; this drain is placed over a sink—a regular sink, with a garbage disposal in it. The blood and bodily fluids just drain down the table, into the sink, and down the drain. This goes into the sewer, like every other sink and toilet, and (usually) goes to a water treatment plant.

You may be thinking that this is biohazardous waste and needs to be treated differently. [If] we can’t put oil, or chemicals (like formalin) down the drains due to regulations, why is blood not treated similarly? I would assume because it is effectively handled by the water treatment plants. If it wasn’t, I am sure the regulations would be changed.

Now any items that are soiled with blood—those cannot be thrown away in the regular trash. Most clothing worn by the decedent is either retained for evidence or released with the decedent to the funeral home—even if they were bloody.

But any gauze, medical tubing, papers, etc. that have blood or bodily fluids on them must be thrown away into a biohazardous trash. These are lined with bright red trash liners, and these are placed in a specially marked box and taped closed. These boxes are stacked up in the garage until they are picked up by a specialty garbage company. I am not sure, but I am pretty sure they are incinerated.

Additionally anything sharp or pointy—like needles, scalpels, etc.—must go into a rigid “sharps” container. When they are 2/3 full we just toss these into one of the biotrash containers.

The biotrash is treated differently, as, if it went to a landfill, then the blood (and therefore the bloodborne pathogens like Hepatitis and HIV) could be exposed to people or animals. Rain could wash it into untreated water systems.

This post originally appeared on Quora. Click here to view.

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Big Questions
Why Does Asparagus Make Your Pee Smell Funny?
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The asparagus has a long and storied history. It was mentioned in the myths and the scholarly writings of ancient Greece, and its cultivation was the subject of a detailed lesson in Cato the Elder's treatise, On Agriculture. But it wasn't until the turn of the 18th century that discussion of the link between asparagus and odorous urine emerged. In 1731, John Arbuthnot, physician to Queen Anne, noted in a book about food that asparagus "affects the urine with a foetid smell ... and therefore have been suspected by some physicians as not friendly to the kidneys." Benjamin Franklin also noticed that eating asparagus "shall give our urine a disagreeable odor."

Since then, there has been debate over what is responsible for the stinky pee phenomenon. Polish chemist and doctor Marceli Nencki identified a compound called methanethiol as the cause in 1891, after a study that involved four men eating about three and a half pounds of asparagus apiece. In 1975, Robert H. White, a chemist at the University of California at San Diego, used gas chromatography to pin down several compounds known as S-methyl thioesters as the culprits. Other researchers have blamed various "sulfur-containing compounds" and, simply, "metabolites."

More recently, a study demonstrated that asparagusic acid taken orally by subjects known to produce stinky asparagus pee produced odorous urine, which contained the same volatile compounds found in their asparagus-induced odorous urine. Other subjects, who normally didn't experience asparagus-induced odorous urine, likewise were spared stinky pee after taking asparagusic acid.

The researchers concluded that asparagusic acid and its derivatives are the precursors of urinary odor (compared, in different scientific papers, to the smell of "rotten cabbage," "boiling cabbage" and "vegetable soup"). The various compounds that contribute to the distinct smell—and were sometimes blamed as the sole cause in the past—are metabolized from asparagusic acid.

Exactly how these compounds are produced as we digest asparagus remains unclear, so let's turn to an equally compelling, but more answerable question:

WHY DOESN'T ASPARAGUS MAKE YOUR PEE SMELL FUNNY?

Remember when I said that some people don't produce stinky asparagus pee? Several studies have shown that only some of us experience stinky pee (ranging from 20 to 40 percent of the subjects taking part in the study, depending on which paper you read), while the majority have never had the pleasure.

For a while, the world was divided into those whose pee stank after eating asparagus and those whose didn't. Then in 1980, a study complicated matters: Subjects whose pee stank sniffed the urine of subjects whose pee didn't. Guess what? The pee stank. It turns out we're not only divided by the ability to produce odorous asparagus pee, but the ability to smell it.

An anosmia—an inability to perceive a smell—keeps certain people from smelling the compounds that make up even the most offensive asparagus pee, and like the stinky pee non-producers, they're in the majority.

Producing and perceiving asparagus pee don't go hand-in-hand, either. The 1980 study found that some people who don't produce stinky pee could detect the rotten cabbage smell in another person's urine. On the flip side, some stink producers aren't able to pick up the scent in their own urine or the urine of others.

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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