For syrup, in a medium saucepan combine sugar, corn syrup, 3/4 cup water, and the 4 oz. strawberries.

Bring to boiling over medium-high. Reduce heat to medium and stir until sugar is dissolved, about 1 minute. Remove from heat. Let cool 30 minutes. Pour mixture through a fine-mesh sieve. Discard solids. Chill syrup before using. You can store it in an airtight container in the refrigerator up to 2 weeks.

For strawberry puree, in the bowl of a large food processor combine the 2 lb. strawberries and the citric acid. Cover; process until smooth. (You should have about 4 cups.) Transfer to an 8-cup freezer container. Cover; freeze until firm, 3 hours to overnight. You want the puree to be firm enough to hold its shape when broken into chunks with a fork. If frozen overnight, let stand at room temperature at least 30 minutes to soften slightly. Using a fork, break frozen puree into 1-inch chunks.

In the bowl of a large food processor combine chunks of frozen puree, strawberry syrup, and the ice. Cover and process until the mixture has an even, icy texture, 3 to 5 minutes. Return to freezer container. Cover; freeze 1 to 2 hours before serving to allow mixture to "reset." For serving, the texture should be like a fine, relatively soft slush. Water ice can be reblended up to three times.