Combine the vinegar, sugar, and salt in a small saucepan and heat just to dissolve the sugar. Remove from heat and pour vinegar mixture into a bowl to cool. Set aside.

Place rice in a heavy bottomed pot, and add water and kelp. Cover and heat over medium high heat just until the boiling point. Remove the kelp and cover again. After 30 seconds, lower the heat and simmer 12 to 13 minutes, or until all the water has been absorbed.

Turn off the heat and let the rice stand, covered, for 10 to 15 minutes. Turn rice into a wide, shallow wooden bowl. Using a flat wooden spoon or rice paddle, spread the hot rice in a thin layer. Toss rice with horizontal cutting strokes to keep grains from separating or getting mashed. While tossing, sprinkle rice with vinegar mixture. While fluffing the rice, cool it quickly with a hand fan. The tossing and fanning will take about 10 minutes. For easy handling, use vinegared rice before it becomes cold. Cover the bowl with a damp cloth to keep warm.