So, what had happened? ... Well, egg shells are made of calcium carbonate – a hard mineral that is similar to calcium phosphate, the substance which our teeth are made of. Acids react with calcium carbonate, breaking it apart into calcium (which is carried off in the water) and carbon dioxide gas. The more acidic a liquid is, the faster the reaction and the more the shell will weaken. The bubbles and froth that form on the egg and on the surface of the liquid are carbon dioxide gas, showing that the mineral is quite literally ‘fizzing’ away in the tart-tasting liquid. Orange juice, which is typically seen as a ‘healthy’ drink, is naturally high in citric acid and therefore causes more dramatic changes than Cola. Commercial soft drinks are extremely corrosive because manufacturers add extra acids to give them a ‘tang’. However, it is energy drinks that are consistently among the worst offenders, typically being as acidic as vinegar! This reinforced how important it is that teeth are well-brushed at least twice a day and any drink, other than water, should definitely be kept to a minimum.