How to Cleanly Clean Clams

To make shellfish in their shells release their sand, you first need to create a condition where they can relax.
In other words, for clams that live in freshwater, plain water is best,
but for cockles, which grow in the sea, you need to prepare saltwater with a similar salinity to seawater,
specifically, 2 tablespoons of salt in 5 cups of water.
Place the shellfish in this water just enough to submerge them slightly, in a slightly dark and quiet place, and
the shellfish will relax and start breathing,
and as a result, they will expel the mud and sand inside.
Once the shellfish have purged the sand, change the water and rub the shellfish against each other to remove any dirt on the shells. Don't forget this step, as the shells can be surprisingly dirty.
Shellfish are prone to spoilage after purging the sand, so it's best to cook them right away.
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