This week’s cover story tackles the legend that New York water is what makes the city’s pretzels and pizzas so good, and asks whether DC Water can create that same sense of pride about the tap here.

In the story, food scientist Chris Loss, a professor at the Culinary Institute of America in Hyde Park, N.Y., says water pH levels and mineral content, particularly calcium and sodium, can affect flavor and texture in foods. For example, hard water, which contains more calcium and magnesium, tends to produce a firmer dough, and soft water produces a softer dough. New York’s water is predominantly soft, while D.C.’s is moderately hard.

But it’s not just baked products that are affected by the water. Ted Russin, a CIA food scientist who focuses on modernist cuisine, says commonly used ingredients in molecular gastronomy—like gellan gum and pectin—are hyper-sensitive to the mineral content of the water.

That means recipes like José Andrés‘ famous liquid olives, which use another calcium-sensitive ingredient called sodium alginate, might work with water from one part of the country and not in an another—unless the recipe is tweaked. Other famous dishes that use gellan gum: the fried mayo at Wylie Dufresne‘s wd~50 in New York and the flaming sorbet at Heston Blumenthal‘s The Fat Duck in the U.K.

“If you have ingredients that are extremely sensitive to calcium, you can see it very literally from city to city,” Russin says. “And that is indicative of the fact that the water you’re using is different from city to city.”

For chefs who travel the world doing demos of their modernist recipes, Russin says it’s probably best to avoid the tap. “A good strategy is to use bottled water to know that your ingredient will behave the same way in that liquid matrix.”