Leave it on the shelf too long and honey begins to crystallize. Heating the honey returns it to its original condition, but if you add water, you could ruin the honey completely. That’s because honey, which is a preservative in its original state, ferments once it’s diluted. In ancient times, honey was used as a food preservative. It works as a preservative because the high concentration of sugar in honey forces the water out of any yeast or bacteria cells that could otherwise contaminate the food. This process, known as “osmosis,” is also what makes salt such an effective preservative. Eventually, the process of osmosis destroys those cells by drawing out all their water–in other words, by drying them up.