How Do Fireworks Actually Work?

iStock
iStock

by Sarah Dobbs

Each year, as the Fourth of July approaches, the sound of explosions starts to become a normal part of the evening. Fireworks have existed in one form or another for around 1000 years, and they show no signs of going away anytime soon. But how do they work? Most of us just know to light the fuse and stand back. Let’s take a closer look …

ROCKETS

fireworks over new york city
iStock

Rocket-type fireworks can produce all kinds of different effects when they go off, but the basic structure of an aerial firework stays more or less the same. Each rocket is made up of the following parts: a mortar, fuses, propellant powder, a shell, a bursting charge, and a collection of "stars." The mortar is the outer container, and the fuse is, of course, the piece that you light. When the fuse burns down, the propellant ignites and shoots the firework into the air.

When it’s airborne, a second explosion is triggered inside the shell by a time delay fuse. The bursting charges set off the stars—small, explosive pellets made of fuel and metallic compounds that create the lights in the fireworks display. Different metals create different colors when they ignite: barium goes green, calcium salts go orange, magnesium goes white, copper is blue, lithium turns red, and sodium becomes gold. And the arrangement of the stars will determine the shape of the explosion—so if they’re packed in a heart shape, they should reproduce that heart shape in the sky.

Other effects can also be built in by adding various ingredients; different kinds of fuel can create sound effects, for example, like the whistling or screaming noises some rockets make as they shoot into the sky. Stars can be made up of layers of different metallic compounds, to create multicolored explosions. And in some more complex fireworks, there may be several stages of explosions; in that case, there are generally multiple fuses inside the shell, and as each burns down, a different explosive goes off.

FOUNTAINS

fountain type fireworks
iStock

Of course, not all fireworks are of the shoot-into-the-air-and-go-bang variety. Fountains don’t take off, and generally don’t go bang, either; instead, they stay where they’re placed and give off a cascade of sparks—like a fountain, but with pyrotechnics instead of water.

Usually conical in shape, fountains consist of a paper or plastic tube, with clay plugs at either end. Inside the tube are a couple of different kinds of fuel, plus the metal compounds that create the sparks. When the fuse is lit, the fuel ignites, and sparks are forced out of an aperture in the top of the fountain.

Again, different metals create different colors and effects. Multi-stage effects can be created by bundling multiple tubes together, so that as one finishes another starts, adding different colors or sound effects to the display.

CATHERINE WHEELS

wheel firework
iStock

Catherine wheels are another common type of firework, and again the same kinds of ingredients are used to create a slightly different effect. Named for the unfortunate Saint Catherine, these fireworks are generally fixed to a pole or a mount, so that they can spin as they burn, creating a spiral of sparks.

Bigger Catherine wheels tend to have a plastic disk at their center, with “gerbs” attached around the edge. The gerbs are similar to fountains, in that they’re tubes filled with the mixture of ingredients that create the effects; when lit, the thrust from the explosives makes the wheel turn as they burn. And again, the effect can be made more elaborate with multi-stage effects and different colors; each gerb might be different, so that the wheel changes as each one ignites in turn.

Smaller Catherine wheels might, instead, be made up of a single long, thin tube coiled into shape around a smaller central disk. Again, the thrust of ignition makes the wheel spin.

SPARKLERS

person holding sparkler
iStock

The only firework you should ever hold in your hand once it’s lit is a sparkler—a Fourth of July staple. Unlike most other fireworks, they don’t explode with a bang, but gently fizzle for around a minute, as a ball of sparks makes its way down a metal wire. And they’re pretty simple: basically, the metal wire is dipped into a pyrotechnic compound that’s made up of a metallic fuel, an oxidizer, and a binding material.

The metallic fuel is what creates the sparks; it’s usually aluminum or magnesium, which creates white sparks, but some sparklers may use iron or ferrotitanium for gold sparks instead. The oxidizer, which provides the oxygen to keep the spark going, is generally potassium nitrate. And then a binding material, a kind of flammable starch, keeps the mixture together, and burns away once the sparkler is lit.

Hopefully, none of that has taken away any of the magic of a good fireworks display. If nothing else, you’ll be able to impress your friends by quietly musing “oooh, barium” next time you see a green firework.

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

Why Do Fruitcakes Last So Long?

iStock
iStock

Fruitcake is a shelf-stable food unlike any other. One Ohio family has kept the same fruitcake uneaten (except for periodic taste tests) since it was baked in 1878. In Antarctica, a century-old fruitcake discovered in artifacts left by explorer Robert Falcon Scott’s 1910 expedition remains “almost edible,” according to the researchers who found it. So what is it that makes fruitcake so freakishly hardy?

It comes down to the ingredients. Fruitcake is notoriously dense. Unlike almost any other cake, it’s packed chock-full of already-preserved foods, like dried and candied nuts and fruit. All those dry ingredients don’t give microorganisms enough moisture to reproduce, as Ben Chapman, a food safety specialist at North Carolina State University, explained in 2014. That keeps bacteria from developing on the cake.

Oh, and the booze helps. A good fruitcake involves plenty of alcohol to help it stay shelf-stable for years on end. Immediately after a fruitcake cools, most bakers will wrap it in a cheesecloth soaked in liquor and store it in an airtight container. This keeps mold and yeast from developing on the surface. It also keeps the cake deliciously moist.

In fact, fruitcakes aren’t just capable of surviving unspoiled for months on end; some people contend they’re better that way. Fruitcake fans swear by the aging process, letting their cakes sit for months or even years at a stretch. Like what happens to a wine with age, this allows the tannins in the fruit to mellow, according to the Wisconsin bakery Swiss Colony, which has been selling fruitcakes since the 1960s. As it ages, it becomes even more flavorful, bringing out complex notes that a young fruitcake (or wine) lacks.

If you want your fruitcake to age gracefully, you’ll have to give it a little more hooch every once in a while. If you’re keeping it on the counter in advance of a holiday feast a few weeks away, the King Arthur Flour Company recommends unwrapping it and brushing it with whatever alcohol you’ve chosen (brandy and rum are popular choices) every few days. This is called “feeding” the cake, and should happen every week or so.

The aging process is built into our traditions around fruitcakes. In Great Britain, one wedding tradition calls for the bride and groom to save the top tier of a three-tier fruitcake to eat until the christening of the couple’s first child—presumably at least a year later, if not more.

Though true fruitcake aficionados argue over exactly how long you should be marinating your fruitcake in the fridge, The Spruce says that “it's generally recommended that soaked fruitcake should be consumed within two years.” Which isn't to say that the cake couldn’t last longer, as our century-old Antarctic fruitcake proves. Honestly, it would probably taste OK if you let it sit in brandy for a few days.

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

What’s the Difference Between Crocheting and Knitting?

djedzura/iStock via Getty Images
djedzura/iStock via Getty Images

With blustery days officially upon us, the most pressing question about your sweaters, scarves, hats, and mittens is probably: “Are these keeping me warm?” If you’re a DIY enthusiast, or just a detail-oriented person in general, your next question might be: “Were these knitted or crocheted?”

Knitting and crocheting are both calming crafts that involve yarn, produce cozy garments and other items, and can even boost your mental well-being. Having said that, they do have a few specific differences.

To knit, you need needles. The size, material, and number of those needles depends on the project; though most traditional garments are made using two needles, it’s also possible to knit with just one needle, or as many as five. But regardless of the other variables, one or both ends of your knitting needles will always be pointed.

While crocheting calls for a similar long, thin tool that varies in size and material, it has a hooked end—and you only ever need one. According to The Spruce Crafts, even if you hear people refer to the tool as a crochet needle, they’re really talking about a crochet hook.

crotchet hook and garment
jessicacasetorres/iStock via Getty Images

Part of the reason you only use one hook brings us to the next difference between crocheting and knitting: When crocheting, there’s only one “active loop” on your hook at any given time, whereas knitting entails lining up loops down the length of your needles and passing them between needles. The blog Darn Good Yarn explains that since each loop is attached to a long row of stitches, accidentally “dropping” one off the end of your needle might unravel the entire row.

Of course, you have a better chance of avoiding that type of manual error if you’re using a knitting machine or loom, which both exist. Crocheting, on the other hand, has to be done by hand. Since machines can create garments with extremely small stitches, some knit clothes can be much more lightweight or close-fitting than anything you’d be able to crochet—and knitted clothes can also be mass-produced.

When it comes to what the items actually look like, crochet stitches characteristically look more like knots, while knit stitches seem flatter and less bulky. However, materials and techniques have come a long way over the years, and now there’s more crossover between what you’re able to knit and crochet. According to The Spruce Crafts, socks and T-shirts—traditionally both garments that would be knitted—can now technically be crocheted.

knitting needles and garment
Sedan504/iStock via Getty Images

And, believe it or not, knitting and crocheting can even be used to depict complicated mathematical concepts: see what a crocheted hyperbolic plane, Lorenz manifold, and more look like here.

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

SECTIONS

arrow
LIVE SMARTER