Motivated By Curiosity And A Desire For The Truth – Part Twenty Eight
Can you fry an egg on a pavement?
“It is so hot outside, you could fry an egg on the pavement”. A curious phrase indeed and one I have always taken as being figurative rather than one grounded in fact. Leaving aside considerations of hygiene – after all, you can never be quite sure what has been on the pavement before – to the enquiring mind, the obvious question is whether it is really possible.
The starting point in our investigation is the humble egg. In order to cook, the proteins in an egg need to have their molecular structure modified by a process known as denature and then coagulate. For the process to start and be maintained to ensure the egg is perfectly cooked, temperatures need to be around 144 and 158 degrees Fahrenheit. This would seem to rule out conducting the experiment in Blighty as temperatures rarely rise above 100 degrees and even then it is so rare that you could be waiting a long time to even attempt the experiment.
The next ingredient in the experiment is the pavement and its particular characteristics. Here I am indebted to some research conducted by Robert Wolke in his book, What Einstein Told His Cook: Kitchen Science Explained. Wolke found that temperatures of pavements can vary depending upon the composition of the pavement, whether it is in direct sunlight or not and on the ambient air temperature. Dark pavements consisting of tar or similar materials absorb more light than concrete ones and so would be the pavement of choice. But, disappointingly, Wolke found that pavements rarely reached a temperature above 145 degrees, frustratingly just short of the minimum temperature needed to cook an egg.
The next problem is that when you crack an egg and pour its contents on to your pavement of choice, the egg will cool it slightly and as the pavement is a poor conductor of heat you will be lucky, without an additional source of heat, to get the temperature back up to a point where the egg will be cooked evenly. The reason we fry an egg in a frying pan is that metal is a good conductor of heat and gets hotter, allowing the optimal temperature to be more easily achieved. If you really wanted to fry an egg al fresco using the natural power of the sun, then you would be better off using the bonnet of a car. As they say, make sure you have the owner’s consent before you try as the mess it leaves may cause offence.
Arizona is a state where temperatures are regularly high and humidity is low. The conditions are such that on 4th July each year – a day when we Brits celebrate the departure of the American colonies from the benevolent British Empire – the good citizens of Oatman hold an annual Solar Egg Frying Contest. As it says on the tin, the contestants have 15 minutes to fry an egg by harnessing the power of the sun. However, to illustrate and confirm Wolke’s findings, they are allowed to use artificial aids such as mirrors, magnifying glasses and reflectors to aid the process. The lack of humidity also helps because liquids evaporate more quickly and so the eggs dry out faster.
So, I suppose, the answer to our question is yes but only with some additional assistance.
Filed under: Science Tagged: can you fry an egg on a pavement, denature, Oatman in Arizona, Robert Wolke, the annuall Solar Egg Frying Contest, What Einstein Told His Cook: Kitchen Science Explained
