Immersion circulators offer a tremendous amount of control over how we cook eggs, making it possible to maintain distinct water temperatures over long periods of time. In the chart at left, we see what happens to a large egg cooked for exactly 40 minutes at a range of temperatures. At the low end, the egg cooked at 130°F (54.4°C) appears raw, but if held at this temperature for a few hours, it will be pasteurized, meaning you can use it to make mayo or a classic Caesar salad dressing without fear of salmonella. As the temperature goes up, the whites begin to set more and more, until, at about 145°F (62.8°C), you finally achieve fairly solid whites and a runny yolk. At higher temperatures, the yolk and whites set more and more fully, until you end up with an egg that’s completely firm throughout.