½ cup ripe berries (blueberries, cherries, blackberries, strawberries, elderberries, raspberries, etc.)
½ teaspoon vinegar
½ teaspoon salt
Fill a strainer with the berries and hold it over a bowl. Using the rounded back of a wooden spoon, crush the berries against the strainer so that the berry juice strains into the bowl. Keep adding berries until most of their juice has been strained out and only pulp remains. Add the salt and vinegar to the berry juice. The vinegar helps the ink retain its color and the salt keeps it from getting too moldy. If the berry ink is too thick, add a tablespoon of water. Store in a baby food jar. Only make a small amount of berry ink at a time and, when not in use, keep it tightly covered.