Wash cucumbers thoroughly and scrub with a vegetable brush, if needed. Remove stems and cut off a slice from each end. (Enzymes at the blossom end of the cucumber may also cause softening.)

To prepare the brine, combine the water, vinegar, and salt in a saucepan. Heat until the mixture boils.

Pack the cleaned cucumbers loosely into hot, clean pint canning jars, leaving a 1/2-inch headspace. Measure the headspace from the top of the food to the rim of the jar with a clean ruler. Add 2 to 3 heads of dill or 3 to 4 teaspoons of dill seed and 1/2 teaspoon of mustard seed to each jar. Place a wide-mouth plastic funnel in the jar and ladle the hot brine over the cucumbrs. Remove the funnel. Release trapped air bubbles in the jar by gently working a narrow rubber spatula around the jar's sides. Add additional brine, if needed, to maintain the 1/2-inch headspace. Wipe the jar rim with a clean, damp paper towel. Any food on the rim prevents a perfect seal. Position a prepared lid and screw band on the jar and tighten according to manufacturer's directions. Place each jar into boiling water of a water-bath canner as it is filled. The jars should not touch. Cover the canner. Process filled jars in the boiling water for 10 minutes. Begin counting the processing time when the water returns to boiling.

When the jars have cooled, press the center of each lid to check the seal. If the dip in the lid holds, the jar is sealed. If the lid bounces up and down, the jar isn't sealed. Unsealed jars should be stored in the refrigerator and used within 3 days. Let jars stand 1 week before using. Label the jars with the contents and date. Store up to 1 year in a cool, dry place. Makes 6 pints (36 servings).