Clean the ramps, keeping only the bulbs. Pack them tightly in sterilized jars. Add 1/4 teaspoon of the alum to each pint. Combine the water and vinegar and bring to a boil. Pour over ramps. Continue making enough liquid to cover all ramps to be pickled. Put the sealed jars in a water bath. Boil 3 to 5 minutes to seal lids.