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enter image description here

We were letting our kids play with sparklers on New Year's Eve, and my friend's son asked his Dad:

What would happen if we threw the sparkler into the water? Would it keep burning under water.

My friend pondered that for a moment - and said it depended if the reaction was based on magnesium or not.

My question is: Are children's sparklers based on a magnesium reaction?

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    $\begingroup$ Probably not, but it would depend on the sparkler. The most common metal is iron powder. $\endgroup$ – MaxW Jan 1 '18 at 4:47
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    $\begingroup$ Many sparklers use aluminium as far as I know. $\endgroup$ – Shoubhik Raj Maiti Jan 1 '18 at 5:45
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    $\begingroup$ Just going by my assumptions on how the world works: water is the standard household method to put out fires. If a product should not be extinguished with water, I would assume big, fat labels on the packaging ‘do not put burning product under water!). $\endgroup$ – Jan Jan 1 '18 at 11:30
  • $\begingroup$ en.wikipedia.org/wiki/Sparkler $\endgroup$ – Nilay Ghosh Jan 1 '18 at 13:00
  • $\begingroup$ Not only will water put out the sparklers, but its recommended to put them into water after use to both rule out any uncombusted material later catching fire and to cool them as a common source of injuries with them is children (and indeed adults) grabbing them by the burnt portion when they are extinguished but still hot. Dousing in water removes that risk. $\endgroup$ – Jon Hanna Jan 1 '18 at 16:25
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What would happen if we threw the sparkler into the water? Would it keep burning under water.

Most likely, not. Water is an effective coolant, so a wet sparkler wouldn't be able to propagate a burn front. Pyrotechnic compositions often severely degrade in a wet air (some might self-ignite and some might loose the ability to burn).

Are children's sparklers based on a magnesium reaction?

The most common sparkler composition I'm aware about is

  • fine $\ce{Al}$ powder as a fuel,
  • $\ce{KNO3}$ as an oxidizer
  • dextrin or other combustible binder
  • Iron coarse powder for orange-ish sparks.

$\ce{Ti}$, $\ce{Al}$ or $\ce{Sb2S3}$ in coarse powder can be used for producing white sparks. Charcoal powder or potassium poly-sulfides can produce redder sparks. To my knowledge, there is no way to produce purple, blue or green sparks.

Exact composition is a delicate balance between gases produces (so sparks were thrown away at meaningful distance) stability and temperature of burn, amount and color of sparks produced, safety and cost.

Please, note. While a common sparkler cannot burn in water, a big slag with same composition and water-proof coating certainly can. But you don't want to be nearby when it happens. Like, at all. An example with a much tamer fuel here:

https://www.youtube.com/watch?v=czwBWB5u6Hg

Also, magnesium is usually avoided in pyrotechnic compositions in favor of aluminum. Magnesium usually produces a lot of thick, white smoke and is more sensitive when stored in real conditions. If aluminum doesn't burn good enough, $\ce{Mg/Al}$ alloy might be used.

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  • $\begingroup$ It is easy to tell sparklers don't keep burning in water. Throw sparklers into water and they go out. The core reaction is an oxidiser + fuel and not a bulk metal burning in air. Oxidisers like potassium nitrate are not water-proof unlike some burnin metals. $\endgroup$ – matt_black Jan 1 '18 at 14:28
  • $\begingroup$ The relevant part of the youtube video starts at 2:37. Ultra slow motion at 3:30. $\endgroup$ – Ben Crowell Jan 1 '18 at 19:00
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To answer the question, let us understand sparkler chemistry. A sparkler consists of:

  1. An oxidizer: potassium nitrate or potassium chlorate. They burn off a mixture and are part of oxidation-reduction reaction: $$ \begin{align} \ce{\underset{potassium nitrate}{2 KNO3 (s)} &-> \underset{potassium nitrite}{2 KNO2 (s)} + O2 (g)}\\ \ce{\underset{potassium chlorate}{2 KClO3 (s)} &-> \underset{potassium chloride}{2 KCl (s)} + 3 O2 (g)} \end{align} $$
  2. Fuel: firework fuel is charcoal and sulfur. Both sulfur and carbon (charcoal) are reducing agents forming sulfur dioxide and carbon dioxide.
  3. Metal powder: aluminum, iron, steel, zinc, magnesium, titanium or ferrotitanium dust or flakes. These metal flakes become incandescent and shine brightly in the presence of oxidizers. If temperatures are high enough, these metal flakes burn. The temperatures of these sparks range from 1800 °F to 3000 °F (1000 °C - 1600 °C)(Ref. I). Many elements heat up and emit at a characteristic wavelength (Ref. II). enter image description here

  4. A combustible binder: binders hold oxidizers, fuel and metal powders together. Common binders are dextrin (a sugar) dampened by water.

  5. Colorants: aluminium, magnesium and titanium all give near brilliant white sparks. Iron produces orange sparks.

Putting all together: these chemicals are mixed together to form a slurry. The slurry is coated on to wire and allowed to dry. When ignited the metal flakes aluminum, iron, steel, zinc or magnesium dust or flakes create the bright, shimmering sparks. As to your question, children sparklers are based on metal oxidizing reactions.

References

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    $\begingroup$ Does the oxidising agent mean that atmospheric oxygen is unnecessary? Including this auxiliary information would make this answer more useful. $\endgroup$ – wizzwizz4 Jan 1 '18 at 13:15
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    $\begingroup$ @wizzwizz4 Yes, sparklers should be able to burn in absence of oxygen, but sparks might be a lot dimmer, since they are partially heated by reaction with oxygen from the air. Also, magnesium generally doesn't give sparks, it usually gives a bright, blinding flame. Magnesium (just like zinc) has rather low vaporization temperature and so is unsuitable for producing of small, bright sparks. Aluminum, iron and sometimes antimony sulfide or titanium are usually used for this. Magnesium usually also produces a lot of white smoke. $\endgroup$ – permeakra Jan 1 '18 at 13:53
  • $\begingroup$ @wizzwizz4 ,depending on the composition of the sparkler ,raecting with atmospheric oxygen is possible.In which case ,it is a combustion reaction.Explosives ignited by gunpowder have their own oxygen.If a sparkler mixture has gunpowder with metal flakes , then oxygen is from Potassium nitrate.Thankyou. $\endgroup$ – Chakravarthy Kalyan Jan 1 '18 at 13:55
  • $\begingroup$ Your conclusion ("children sparklers are based on metal oxidizing reactions.") doesn't match the content you wrote. The primary reaction is based on gunpowder (fuel+oxidant) and the metal burning is a side effect not the primary combustion taking place (at least that's what you described earlier in your answer). So it won't work under water. $\endgroup$ – matt_black Jan 1 '18 at 14:25

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