How Do Fireworks Get Their Colors?

deymos, iStock / Getty Images Plus
deymos, iStock / Getty Images Plus

Want to impress your friends while you wait for this year’s fireworks display to begin? Wow them with your knowledge of basic chemistry and let them in on the secrets to the rainbow beauty of the night sky on the Fourth of July.

Small pellets, charmingly named "stars," are the key to the fireworks's colors, EarthSky reports. The stars are filled with different combinations of metal salts that each add a bright color to the firework when it explodes.

Different chemical elements correspond with different colors: strontium carbonate for red, calcium chloride for orange, sodium nitrate for yellow, barium chloride for green, and copper chloride for blue. Purple fireworks are created much like you might create purple paint—by mixing red and blue.

According to LiveScience, when you light the fuse on the outside of the fireworks's thick tube, the flame ignites a pouch of black powder inside known as the lift charge, which causes the shell containing the stars to catapult into the air. As it rises, a time-delay fuse begins to burn within it and, by the time it reaches its maximum height, the shell bursts, causing the stars inside to color each strand of the explosion.

Paul Nicholas Worsey, fireworks expert and professor of mining and nuclear engineering at the University of Missouri at Rolla, told LiveScience that red and green are the easiest colors to create, while blue is more difficult. Worsey says gold is best if you want your firework to keep its color for a long time, maybe even until it hits the ground.

The trick behind those especially crowd-pleasing fireworks that change color after they explode is simple: The stars are simply coated in multiple metal salts. Once you see the firework’s second color, that means the stars burned through their outer layer and reached a different metal salt—kind of like licking a Gobstopper.

For another way to impress your friends this fireworks season, learn the names of these 10 fireworks effects so you can call them out as they burst.

[h/t EarthSky]

The Reason Why No Photography is Allowed in the Sistine Chapel

Wikimedia Commons
Wikimedia Commons

As the home of some of the greatest works of art produced by humanity, the Sistine Chapel in Vatican City is a popular tourist destination (to put it mildly). If you've been one of the 4 million visitors to the famous landmark each year, you've probably learned of one aspect of the room filled with Michelangelo's beautiful, biblical frescos that tends to come as a surprise to first-time guests.

There's no photography or video allowed in the Sistine Chapel.

Yes, despite the rules that encourage quiet contemplation of the fantastic, eye-popping art that adorns nearly every inch of the walls and ceiling of the Sistine Chapel, visitors to the chapel will find their experience peppered with terse shouts of “No photo! No video!” from security guards. The prohibition against photography has been in place for several decades, and while many assume that the no-photography rule is in place to prevent the flashing of cameras from affecting the art, the real reason dates back to the restoration of the chapel's art that began in 1980 and took nearly 20 years to complete.

Restoration of Daniel in the Sistine Chapel
Michelangelo, Wikimedia Commons // Public Domain in the United States

When Vatican officials decided to undertake a comprehensive restoration of Michelangelo's art in the chapel, the price tag for such an endeavor prompted them to seek outside assistance to fund the project. In the end, the highest bidder was Nippon Television Network Corporation of Japan, whose $3 million offering (which eventually ballooned to $4.2 million) was unmatched by any entity in Italy or the U.S.

In return for funding the renovation, Nippon TV received the exclusive rights to photography and video of the restored art, as well as photos and recordings of the restoration process by photographer Takashi Okamura, who was commissioned by Nippon TV. While many initially scoffed at the deal, the high-resolution photos provided by Nippon offered a hyper-detailed peek behind all of the scaffolding that hid each stage of restoration, and eventually won over some critics of the arrangement.

As a result of the deal, Nippon produced multiple documentaries, art books, and other projects featuring their exclusive photos and footage of the Sistine Chapel restoration, including several celebrated collections of the photographic surveys that informed the project.

The ban on photography within the chapel remains in effect despite the waning of the terms of Nippon's deal. In 1990, The New York Times reported that Nippon's commercial exclusivity on photos expired three years after each stage of the restoration was completed. For example, photos of Michelangelo's epic depiction of Last Judgment were no longer subject to Nippon's copyright as of 1997, because that stage of the restoration was completed in 1994.

For the record, Nippon has stated that their photo ban did not apply to "ordinary tourists," but for simplicity's sake—lest some professional photog disguised himself in Bermuda shorts and socks and sandals—authorities made it an across-the-board policy.

Last Judgment in Michelangelo's Sistine Chapel
Michelangelo, Wikimedia Commons // Public Domain in the United States

The “No Photos! No Video!” rule remains in place for the Sistine Chapel (though as some recent visitors can attest, its enforcement isn't exactly strict). Given the damage that can be caused by thousands of cameras' flashes going off in the chapel each day, it's no surprise that Vatican officials decided not to end the ban when Nippon's contract expired.

After all, the chapel houses some of the greatest art in the world—and a gift shop stocked with souvenir photos, of course.

Where Do Cobwebs Come From?

S847/iStock via Getty Images
S847/iStock via Getty Images

It’s a hallmark Halloween decoration: Sticky, burdensome cobwebs that stretch across ceilings and walls, remnants of spider occupations gone by. Some homes don’t need the artificial version, with real cobwebs a persistent nuisance that requires perpetual prodding with a duster. Where do these cobwebs come from?

The term cobweb is used to describe any web spun by a member of the Theridiidae family of spiders, made up of a number of species that tend to be found in residential homes. But colloquially, people tend to use the phrase to refer to abandoned threads of webbing they wind up clearing with brooms. When in use, these cobwebs tend to be sticky but unstructured, lacking the amazing and intricate design of webs woven by other species. Spiders make webs in the hopes of trapping prey, but if one location isn’t proving fruitful, they’ll move to another. That—along with the death of the web owner—can lead to abandoned cobwebs that eventually fall apart, dangling listlessly from room corners, collecting and trapping dust.

It’s that flypaper characteristic that likely results in you noticing a cobweb for the first time. As particles accumulate, the cobweb becomes more visible. You may also notice single web strands in isolation. These are likely from a spider’s interior travels as they search for a place to settle in.

If you want to reduce the cobweb clutter, regular dusting will reduce both their visibility and their existence. You can also look for and seal cracks around windows or doorways that might provide access. Maybe wait until after Halloween, though.

[h/t realtor.com]

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