Purging clams means freeing them of any sand and grit that is held inside of their shells. Clams must be purged before cooking so that you don’t end up with sand in your food!   To purge clams, fill a large bowl with a mix of cold (never hot!) water and, ideally, fine sea salt. In order to match the salinity of seawater, mix about ¼ cup salt into 3 to 4 quarts water. Then, carefully immerse the clams in the salted water and let them soak for about one to two hours to allow the clams to purge sand from their shell.  Remove the clams from the water– do not run the clams through a strainer because you will cover the clams in sand. You should see sand in the bottom of the bowl. Repeat this process if you think necessary (i.e., if the water is very cloudy with sand.)   Rinse the clams with cool water and then they are ready to use!