Effectively, they are steel containers submerged in water baths used to slowly bring food up to a constant temperature and keep it there. They are extremely useful when you need to serve the food over a longer period of time, but want to make sure customers are receiving the same consistent product. Caterers will usually have a number of Bain Maries for storing and serving a selection of food and they’re often used for transporting and serving at events away from the preparation area - particularly useful when the food temperature needs controlling. They range in size from a single bain marie to a 9 container bain marie.