# Pancake Day As You’ve Never Seen it Before

9th February, 2016 by

The science behind the perfect pancake could be useful in the effective treatment of glaucoma.

Every year we celebrate Pancake Day on Shrove Tuesday. Pancake Day is believed to have originated as a day on which to use up indulgent ingredients the day before the start of the fasting season of Lent. Another opinion on its origin is from the Pagan holiday celebrating the arrival of spring, within which the round warm pancakes were in effect symbolising the sun.

This years Pancake Day takes on a whole new meaning by becoming a mathematical model! UCL published an article today – Understanding the physics of pancakes to save sight” – which investigates the textures and patterns of pancakes with the aim of improving surgical procedures for treating glaucoma.

This might sound somewhat bizarre, but pancakes actually have a relationship with the eyes retina, the light sensitive layer of tissue inside our eye. The illness glaucoma – which can lead to blindness and has no cure – occurs when fluid builds up in the eye exerting pressure on the retina. In essence, glaucoma can be described by fluid dynamics. So a team of researchers at University College London, led by Ian Eames, is investigating how structure and pattern of tissue changes with the presence of liquid, and are hoping to use this research to treat glaucoma more effectively. Believe it or not, this phenomenon can be studied using the process of pancake making.

So how does it work? Ian Eames et al published a paper in Mathematics Today: How to make the Perfect Pancake, and are combining kitchen experiments with mathematical theory. A pancake is characterised by its aspect ratio (the ratio of its width to its height) and the bakers ratio (the ratio of mass of liquid (milk or water) to flour). The experiment is as follows: The patterns on the top and bottom of pancakes are analysed in a kitchen study and explained in terms of how the vapourised liquid in the batter escapes. We determine the properties of a perfect pancake.

Pancakes come in different shapes, sizes and thicknesses and are cooked by heating the batter, causing the liquid to evaporate. Understanding the cooking process, which is a conversion from a free flowing liquid to a soft solid, should lead to a method of making the perfect pancake. In the experiment the researchers kept the amount of flour and eggs per pancake constant while varying the amount of milk. A 24cm diameter pan was used to cook an equal mass of batter of each liquid variation. It was poured into the centre of the pan and left to flow freely. The heat source was always constant.

The two categories which were evaluated are the shape of the pancake, and the pattern on the top/bottom of it. They found five distinct patterns emerging in the cooking process: the escape path of vapour from the bottom of the pancake largely determines how the pancake cooks and the patterns.Depending on whether the vapour easily escapes or is trapped in the pancake batter leads to a change in pressure. The way of evaporation gives rise to the patterns such as radial spokes or a smooth pattern. These patterns depend on the thickness of the batter; in other words the fluid content decides the evaporation pattern.

The thicker batters created craters on the bottom surface caused by the vapour being trapped during cooking, lifting the pancake unevenly from the pan. The top surface was filled with craters due to the non-uniformity of the thickness. The thinner batters cooked to create an even colour on the bottom of the pancake as the evaporation of liquid is released smoothly. The very thin batters created dark spots on the bottom with tiny holes on top from the evaporation.

There were two main trends observed. Dr Yann Bouremel, co-author of the paper, said: If the batter spreads easily in the pan, the pancake ends up with a smooth surface pattern and less burning as the vapour flow buffers the heat of the pan. We found a thin pancake can only be created by physically spreading the batter across the pan and in this case, the vapour tends to escape through channels or diffusion.

So how does this relate to the treatment of glaucoma?

Professor Sir Peng Khaw, one of the co-authors of the pancake paperand the Director of the NIHR Biomedical Research Centre at Moorfields Eye Hospital and UCL Institute of Ophthalmology, said: We work on better surgical methods for treating glaucoma, which is a build-up of pressure in eyes caused by fluid. To treat this, surgeons create an escape route for the fluid by carefully cutting the flexible sheets of the sclera. We are improving this technique by working with engineers and mathematicians. Its a wonderful example of how the science of everyday activities can help us with the medical treatments of the future.”  (See more here). We suppose that the researchers are looking for the best possible escape path of the liquid trapped in the eye without damaging the retina surface.

This is very cool stuff! Who would have thought that a simple delight such as a pancake would have the ability to mimic a human eye condition? This is one of the things I love most about science – its part of everyday life without us sometimes being aware of it. Wishing everyone a Happy Pancake Day from all of us here at UK2!

Tweet us a picture of your best pancake effort @UK2!

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