Physics

Bring Up Fireworks—How Do We Make Colours Explode

/ Sylvie Blouin / Leave a comment

Living in Canada, I can say that Fireworks are directly associated with Summer. Now that we are in the heart of August, we are left with one last month to enjoy the rest of the season. Yet, in these earlier summer months, we have been fortunate enough to enjoy many fireworks displays and that despite our current COVID-19 pandemic restrictions. More precisely, in Quebec, Canada, we have been able to enjoy firework shows on St John the Baptist Day (24 June, provincial holiday), on Canada Day (1 July, national holiday) and in many festivals taking place around the province. For instance, there is one festival in my hometown, called ‘le Festival du Lac des Nations,’ which has been held every year except for, understandably, 2020. This year’s edition of the festival was held simultaneously in theatres with a prefixed number of people possible to accommodate, and virtually. Though, for the pyrotechnic display, only the date was known; its location remained secret. Yet, the organizers made sure to publicize a list of relevant sites to ensure that everyone could enjoy the spectacle. It was an excellent formula to avoid gathering, but something was missing….its associated music. 

Anna-Louise|Pexels.com

Typically five Canadian provinces compete throughout this festival with fireworks that must match a preset soundtrack. Each competitor also gets evaluated based on the complexity, diversity and placements of pyrotechnic explosions. Unfortunately, uncontrollable and yet understandable circumstances have led to the calling-off of the competition this year.  Luckily, we still had an opportunity to witness fireworks as the festival had planned for one spectacular pyrotechnic event. Conveniently, the show followed the conventional approach and the fireworks followed the rhythms of a preset soundtrack. We could listen to the playlist on popular radio channels that broadcasted the event. Even though this plan seems very well organized -giving people the chance to tune in to the music, or not- meant that we had to keep in mind the wishes of everyone nearby. Having chosen a particularly well-sought site, I had to comply with my surroundings and turn off the volume. Still, I should have thought more carefully about this whole thing and brought headphones. It simply didn’t occur to me to take them since I was with friends. Anyway, I’ll know better next time. Without the soundtrack, the fireworks display was still remarkable. It for sure lived up to its name of being the biggest in Sherbrooke yet. 

During the show, we saw smiley faces, hearts, planets, and many other intricate shapes. This demonstration made me gasp at the increased complexity and diversity that pyrotechnic companies had been able to create in such a short window of time. Not only did the shapes contribute to their complexity, but also did the colours of each firework. They were able to reflect the whole visible light spectrum from red to violet and sometimes gold and even white. One can only wonder about how this is even possible. We could even consider this whole technology as magic. If only I didn’t know any better, I sure could believe it.

Anyhow, I first learnt about the formation of the different colours in elementary school. Before jumping into the nitty-gritty of the mystery, my teacher told us about the nature of fireworks. Like any fire, you first need fuel and an oxidizer. For example, in a bonfire, the wood acts as fuel and the ambient air as the oxidizer.  In the fireworks’ case, you need a much more powerful oxidizer than air which can release more oxygen to interact with the fuel. Good choices of oxidizers are chlorate and perchlorates. Fuel will typically be charcoal or sulphur. In this case, wood would not be a good fuel source since they need much more power to propel in the air and explode. However, these two alone do not explain from where the colours originate. They are, in fact, resulting from the addition of colouring salts. If you never tried burning table salts, you should. It will produce a rich yellow-orange light. This colour is a result of the combustion of sodium. Yet, even with these three elements, one thing remains. A crucial binder is required to keep all those elements glued together in the form of a pellet. Usually, the binder is a type of starch known as dextrin. 

MATSUDA Akihiro|Pexels.com
Sami Anas|Pexels.com

So, many salts (or metals) are each responsible for producing different colours of fireworks, starting with sodium that makes yellow-orange light. Still, we are missing the information about what metal is responsible for the other colours, so here is a list. Strontium produces the dark red light; lithium, lighter red; calcium, orange; sodium, (you guessed it) yellow; barium, green; copper, blue; cesium, indigo; potassium, violet; and finally, rubidium, reddish-violet. Gold and white light, though, can be created by a wide range of metals. For gold, we may use charcoal, iron and lampblack, and for white, we may decide to burn titanium, aluminum, beryllium or magnesium. Actually, you may be surprised to know that aluminum is the metal used on the sparklers to produce silver and white flames. As for the sparklers that create gold flames, we use iron. Titanium can also serve to make pure white; and ferrotitanium, bright yellow.

Colour is only one facet of the intricacy of fireworks. As mentioned previously, shapes can also play an important role. It helps bring richness to the show and wonder to the spectacle. The pattern created comes from how our fireworks are assembled together. So, creating a smiley shape is as easy as arranging the small combustible pellets to form our dearly beloved emoji. Yet, there can be instances when the science goes wrong, and the firework doesn’t display the shape intended to present. These uncertainties are the reason why we fire several copies of the same fireworks. In this case, if one doesn’t show correctly, then at least one of the others can create the desired shape.

However, even if fireworks are impressive and merit every single one of their applause, we shouldn’t try to reproduce a show in our very own backyard. Fireworks can be pretty hazardous and, if carelessly handled, can produce serious harm; sometimes, even death. We all need to remember that these pyrotechnic tools include flammable and explosive materials, and as such, can release tremendous amounts of energy, like heat. For instance, you should never ignite fireworks during a heatwave as it may trigger a forest fire. Moreover, handling fireworks might not be the only hazard that these carry. 

We should be aware that the sounds produced from the explosion are loud enough to frighten and stress both humans and animals nearby. A typical animal behavioural response to stress is to hide or flee. These behaviours could lead new parents to abandon their offspring in exchange for safety. Chemical pollution also shouldn’t be ignored. Upon explosion, the heavy metals used to produce the colours of the fireworks can escape into the environment. The release may have detrimental effects and possibly neurological impacts on both us and our surrounding fauna. For instance, some fishermen have previously observed that some fishes were distraught following fireworks, particularly antimony sulphide-based fireworks. It is wise to understand that all parts of the firework composition may involve the presence of toxic chemicals. Thus, airing on the side of caution, we should resist the temptation to fire them. Yet, this does not mean that we shouldn’t enjoy the fleeting moments when fireworks happen in our vicinity. 

Peter Spencer|Pexels.com

I can’t resist feeling both respect and admiration for this technology. The former comes from the power it holds that is enough to cause harm, and in consequence, we should all keep a reasonable distance from it. The latter because of the technological advances scientists helped create. Pyrotechnic shows do not only require chemists and scientists, but they also need artists. They need art to produce a marriage of shape and colours that can’t help but produce awe in anyone watching. And now, even knowing about its underlying conception, I can’t repel the idea that fireworks are just entirely magical.

I thank you infinitely for reading this post and if you would like to know more about the mysteries that surround us, please join my subscription list to keep up with my newest content. If you have any questions, please add them to the comment section and I’ll make sure to answer them as soon as humanly possible.

Get new content delivered directly to your inbox

Environment

Bring Up Biophilia—What makes us particularly attracted to nature

No one can dismiss the amazing feeling we get after spending some time in nature. We instantly feel relaxed and reinvigorated. Some might attribute this effect to time spent far away from work, and even though they could be correct, it is not the whole picture. Biophilia is a relatively new concept that brought the…

Physiology

Bring Up Blood—How our oxygen gets carried throughout our body

Good evening my dearest followers, Please, take a moment to enjoy this excerpt for my newest post (Bring Up Blood). We could most certainly not live without blood. It is absolutely essential for the survival of our most distant limbs and organs. Even though almost all of our respiration is thanks to our respiratory organs,…

Advertisement

Bring Up Hearing—Where is this sound coming from

/ Sylvie Blouin / 1 Comment
Andrew Mckie|Pexels.com

The type of stimulus that first recruits my awareness in the morning is most probably auditory. The sound may be coming from outside, like bird songs, or it could be coming from indoors, like my scheduled alarms. It certainly sounds more pleasant to be awakened by the tweeting of the birds, but living in Montréal, hearing the rumblings of heavy machinery is definitely more likely, which is sincerely irritating. This observation raises a particular question about the pleasantness of sounds and its origin. To answer the how and where its pleasantness comes from, we must know the differences between music and noise. However, it may not be as straightforward a question as it may seem.

The nature of sound is quite interesting as it doesn’t have any material constituents. Nobody was ever able to grab sound, to see sound or to taste sound. We cannot do any of those because a sound is a product of vibrations that spread through the air (or water) as acoustic waves. Depending on the properties displayed by the acoustic waves, the sound can be perceived differently. On the one hand, we can interpret a sound to have different levels of loudness which is attributed, in most parts, to the amplitude of the waves. The greater the amplitude (the height from the resting point to the top of the wave), the louder we recognize the sound to be. On the other hand, a sound can also have a different pitch depending on the specific period, frequency and wavelength it displays.

Acoustic waves generally follow the pattern dictated by sinusoidal functions, which we probably all encountered at some point in High School. For acoustic waves, the amplitude -determined by the height between the maximum and the x-axis- is still conserved. We only need one tiny adjustment; the x-axis now becomes known as the resting point. A period becomes the time it takes for the sound to complete its cycle. The frequency becomes the number of cycles completed within a specific time, which we typically calculate in Hertz (Hz; cycle/second). The wavelength is then the amount of distance sound can travel per period. They (all three) remain closely related to one another; the frequency is inversely proportional to both the period and the wavelength.

Charles Parker|Pexels.com
Sunsetoned|Pexels.com

These properties mean that the longer the wavelength (smaller Hz) is, the lower the frequency becomes. And as for the pitch, the inverse is also true. Although, there exist limitations to this observation. Namely, the limit of our human ear. They only possess the ability to detect sound within the range of 64 Hz to 23 kHz. However, some animals can perceive sound in much greater ranges than we can. Dogs are one of these animals with a hearing capacity between 67 Hz to 45 kHz. Nevertheless, cats take the lead here with their remarkable hearing sensibility ranging from 45 Hz to 67 kHz. This characteristic may describe their incredible success at hunting little prey such as rodents, which can emit sound as high as 100 kHz.

Depending on what the sound passes through, the speed and its direction can and will vary. Water, being thicker than air, will most definitely slow down sounds and redirect at a much greater angle than what we can observe with air. This redirection is also called refraction, which is the same phenomenon that is responsible for the shift of the image when seeing an object immersed in water. If, for whatever reason, you absolutely have no idea of what I am referring to, try this: take a transparent glass of water and partly submerged an opaque object in it (could be anything). You can see that the object seems broken when it passes through water, and that is refraction.

Agung Pandit Wiguna|Pexels.com

Even though there are many properties characterizing sound, the ear is principally reactive to one, frequency. Amplitude will only play a background role to infer loudness to the sound. Our ear, which is our hearing organ, seems particularly attuned to pitch and loudness. As sounds are created, through the contact of objects causing vibration, it produces the acoustic waves as mentioned earlier. Upon hitting the auricle, the sound will be amplified and modulated before reaching the eardrum. The vibration, amplification and modulation create a chain reaction in the middle ear, which activates the ossicles (Malleus, Incus, and Stapes). The ossicles will then transmit the sound wave to the cochlea in the inner ear. In the cochlea, we can find plenty of hearing nerves, which connect to the brain. Once at the brain, the signal becomes interpreted to allow identification, classification and interpretation of the sounds.

It is the brain that is responsible for determining the pleasant nature of the sound we hear. Some people are affected by a condition that renders them unable to enjoy or derive any pleasure from music. This condition is known as musical anhedonia. It is a neurological condition caused by reduced connectivity in subcortical regions related to reward. Although these people might not be able to enjoy music, they can most definitely identify it, unlike those suffering from music agnosia. Despite their ability to hear, the latter cannot even tell the difference between music and noise. Individuals typically acquire this condition following an injury to at least one of the temporal lobes or after a unilateral stroke. These two conditions splendidly reveal the importance of the brain’s interpretation role in the perception of music.

Anna Shvets|Pexels.com

There is one more aspect of sound that I haven’t introduced yet: timbre. This term is often replaced by “sound quality” as it refers to the nature and distinctiveness of a sound, in other words, the pattern of harmonics. For instance, a violin will never sound exactly like a piano, even though you decide to play the same note at the same loudness level. Now, despite having described all these aspects and properties of sound, we still fall short when it comes to explaining where the pleasantness of music originates. However, what we have discussed so far was more related to sound itself and not music. What makes music is its rhythm or tempo, which creates sound arrangements through time, that can either be pleasing or not. When considering music perception, rhythm and pitch are the most central aspects involved.

Christa Grover|Pexels.com

Now that I have introduced rhythm, we can start approaching closer to an answer. There are many factors involved; familiarity, distortion and reverb. As a general rule, we prefer sounds and/or patterns of sound that we are more familiar with; the ones we heard before. Usually, music acquires its different alluring attributes over relatively long periods. Music is pretty conservative as a general rule. However, beyond familiarity, there are distortion and reverb, each responsible for some aspect of pleasantness. Distortion comes from making the tone of the sound imperfect by changing its original form. Reverb is pretty much like echo, but instead of having the sound coming back to you in two parts, it comes back to you almost immediately. Although, not fast enough for merging with the original sound. The result becomes a continuation of the sound. We can often witness reverb in churches or even (ahem!) the shower. Reverb partly explains why it’s so delightful to hear ourselves signing in the shower. Yet, I cannot say I do much of that; my showers are always too short for that. How about you?

I thank you infinitely for reading this post and if you would like to know more about the mysteries that surround us, please join my subscription list to keep up with my newest content. If you have any questions, please add them to the comment section and I’ll make sure to answer as soon as humanly possible.

Get new content delivered directly to your inbox.

Art

Bring Up Tattoo—How it can be possible to mark our skin permanently

Not all appearance alterations are created equal; some may be more short-lived and others more permanent. If you think of tattoos, they mostly belong to the second category. So thinking carefully about certain aspects of the tattoo becomes imperative. Things like the symbolism or the artistry behind your new piece shouldn’t be random. Choosing a…

Human Development

Bring Up Grad School—What Is the Reality Behind Higher Education

For people who want to pursue studies after completing high school, university studies may look very attractive. So, undergraduate studies may lead to graduate studies. However, undergraduate studies are not the same as graduate studies. The latter is not only more complicated, but it is also very different. First of all, contrary to your undergrad,…