1. Scrub clam shells thoroughly under cold water running from the faucet. Use a sturdy scrubbing brush. Rinse thoroughly in the running water. Discard any that are even slightly opened.
2. Place the clams in a large kettle with the water and salt. Cover, bring to a boil and simmer 5 minutes, or until all shells have been opened.
3. Strain the liquid through scalded cheesecloth.