Lift it out of the water each time. Do not let the fruit stand in water. The amount of fruit needed to yield the amount of juice called for in the recipe varies with the juiciness of the particular fruit used. The method of juice extraction differs with various kinds of fruit. Juicy berries may be crushed and the juice pressed out.
Heating is needed for firmer fruits to start the flow of juice.
Usually some water is added when the fruit is heated. Put the prepared fruit in a damp jelly bag or fruit press to extract juice. Restrain pressed juice through a double thickness of damp cheesecloth or a damp jelly bag. In a saucepan, soften gelatin in grape juice and lemon juice. Remove from heat.