You have asked an interesting question! Most questions about cooking and food preparation can be rephrased as chemistry questions!Let's first think about what "pickling" is and then we'll get to "how long it takes" to pickle that egg (by the way, I love to eat pickled eggs - my grandmother, who is 96 years old, still makes them, pickling them in beet juice so that they look like bright purple Easter eggs!).

So, what is happening when we "pickle" a food?Basically, we use an acidic substance to modify the components of the food in such a way that we "preserve" the item, and this usually modifies the taste as well.Okay, so what happens when we put an egg in an "acidic substance" like vinegar (the most common pickling solution)? By the way, beet juice is also acidic, which is why that works for my grandmother.

There are two ways to set up this question. If we want to "pickle" a raw egg, which is a pretty common science classroom experiment, we take the egg (shell and all) and place it in a mixture of vinegar and water. The shell is made primarily of calcium carbonate. The acid reacts with this material, essentially dissolving it away. There is clear membrane left behind, allowing you to see inside the egg. The entire egg gets very rubbery feeling, and you can even roll it up in a cigar shape.

The second way to think about pickling is as the true food preservation method - you take a hard boiled egg, gently remove the shell, then place the cooked egg in the acid solution. In this case, the low pH of the pickling solution prevents bacteria from growing, and also modifies the taste of the egg slightly - the acid "reacts" with the egg proteins.

Now to the question of "how long?" Since we are essentially talking about a chemical reaction, let's think about what might influence that.Temperature maybe? The strength of the acid? The size of the egg? All of these!

In general, the "rubber egg" experiment will take roughly 24-48 hrs while typical pickling recipes for hard cooked eggs specify several days to weeks.

Pickling an egg involves hard boiling eggs, peeling them, and then immersing the eggs in a solution made up mainly of vinegar, salt, and spices ( this solution is also boiled before adding it to the eggs). Over time the eggs absorb the vinegar solution and become flavored by the spices. The vinegar and salt also help to preserve the eggs. While this definitely inhibits microbial growth, it is still possible to get food poisoning from pickled eggs that haven't been prepared or stored properly. To avoid this, it is very important that the eggs are fully cooked and that the pickling solution is thoroughly boiled. When pickling, the eggs should be stored in the refrigerator for a minimum of 2 days, although some people leave it for 1-4 weeks. After pickling, the eggs are traditionally stored at room temperature. But, to be safe, I would suggest keeping them in the fridge.