1 1/2 teaspoons citric acid
6 tablespoons lukewarm water
5 quarts skim milk
1/4 rennet tablet
6 tablespoons coarse kosher salt
16 cups water
8 cups cold water
4 ice cubes

In a glass or enamel bowl, dissolve citric acid in 4 tablespoons of the lukewarm water, stirring with a slotted stainless steel spoon. Pour the milk into a large enamel stockpot. Add dissolved citric acid, stirring for 1 minute with the spoon to distribute well. Heat to 88 degrees F (using a candy thermometer) over medium heat.

Dissolve rennet in remaining 2 tablespoons lukewarm water, crushing the tablet and stirring with the stainless steel spoon. When the milk mixture reaches 88 degrees F, remove from heat and stir in dissolved rennet. Cover the pot and set it aside for 20 to 25 minutes, until the milk has coagulated into a thick, custard-like mixture. Using a long knife, cut the milk into approximately 1/2-inch curds (cut through, but do not break up). Cover the pot and set it aside for 5 minutes more.

Uncover the pot and return it to a very low heat for about 15 minutes, stirring constantly with the stainless steel spoon, until the mixture reaches a temperature of 106 degrees F. Remove from heat and continue to stir for 20 minutes. By now, the curds will have hardened into pellets surrounded by the liquid they gave off.

Line a colander with a dampened double thickness of cheesecloth and place it in the sink. Pour the mixture into the cheesecloth and let the liquid drain for 15 minutes.

Meanwhile, bring the 4 quarts water to a boil.

The curds will have solidified while draining. Remove the mass from the colander. Cut into long strips about 1-inch square and place them into a large bowl. Add salt to boiling water and stir with a wooden spoon until salt dissolves. Pour salt water over the strips. With wooden spoon, stir the strips for 7 to 10 minutes, pushing down and then pulling up so as to stretch them, until a glossy, stringy mass is formed.

Transfer the mass to a cutting board and knead for about 2 minutes to form a ball. Place the ball in a bowl with the cold water and ice cubes for 5 minutes.

Remove the cheese and dry it with paper towels. The mozzarella is ready to be used. Store it, wrapped in plastic wrap, in the refrigerator for up to 2 weeks.

This makes 3/4 pound.