Some restaurants celebrate customers鈥� special occasions by planting burning sparklers onto food, showering it with sparks. Sparklers typically contain an oxidising agent such as potassium nitrate, which yields nitrite as a combustion product. The European Food Safety Authority specifies a safety limit for nitrite ingestion of 3.7 milligrams per day per kilogram of body weight. How much nitrite would someone ingest by eating a slice of sparkler-enhanced birthday cake?
鈥� Sparklers used on cakes will conform to a British European Standard, BS EN 15947 category F1, which means they will contain less than 7.5 grams of explosive. In fact, sparklers used on cakes are likely to be somewhat smaller than this, containing, say, 3 grams of explosive. The black powder (sometimes called gunpowder) used as the explosive is typically about 75 per cent potassium nitrate, which amounts to about 2.25 grams per sparkler. If it all decomposes to potassium nitrite, it would yield about 1.9 grams of this chemical.
鈥淵ou could have three slices of sparkler-enhanced cake a day and stay within the safety limit for nitrite鈥�
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This would be scattered all over the place, but let鈥檚 say 1 gram goes onto the surface of the cake. If the cake is then cut into 12 slices, that is 0.08 grams of potassium nitrite per slice, which is just over 1 milligram per kilogram of body weight for a 70 kilogram person.
So you could have three slices of sparkler-enhanced cake per day and stay within the European Food Safety Authority ingestion limit of 3.7 milligrams per day per kilogram of body weight. However, it鈥檚 not likely that this amount of potassium nitrite is produced.
It is also worth noting that potassium nitrite is a food additive, often labelled as E249.
Peter Borrows, Amersham, Buckinghamshire, UK
鈥� I think we are all safe from normal sparklers fired off one at a time on a cake, even if we don鈥檛 cut off the black bits in the icing.
However, there are not only sparklers, there are also mega-sparklers. These are very dangerous 鈥� and illegal in some countries. I have only seen them at Australian New Year celebrations, on a beach. As they say: Don鈥檛 try this at home.
They consist of perhaps 150 normal sparklers bundled together with wire. One central sparkler is left sticking up, used as the ignition point. Combustion is almost instantaneous, a column of flame and smoke shoots up over a metre high and I suspect it forms a mushroom cloud, although it was too dark to tell.
Standing downwind with a glass of wine and a cupcake, as the mushroom cloud settles out, would surely mean that the wine and the cupcake would exceed a number of Australian and European food safety standards.
Andrew Carruthers, Beaconsfield, Quebec, Canada
鈥� The main nitrogen-containing chemical produced when using potassium nitrate in pyrotechnics is nitrogen gas, not potassium nitrite. I suspect the amount of nitrite produced is very small, if there is any at all.
Eric Kvaalen, Les Essarts-le-Roi, France
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