How to Purge Sand from Clams

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Western littleneck clams, ready to purge
Photo by Hank Shaw

There is a library’s worth of bad information out there about how to purge sand from clams, ranging from mythical to downright scary. Hopefully I can set the record straight. Here’s what you need to know to get the grit out of your clams.

Let me start by saying that the vast majority of clams, mussels and oysters you buy in the market have been purged already. You will almost never need to purge your clams if you bought them at a supermarket. The exception is if you buy from a small purveyor, and in that case just ask: Have you purged your clams?

Wild clams and mussels are an entirely different story.

They should always be purged, clams especially. Different clams need different purging times, too, depending on how and where they live. Hard shell clams in clean sand, like Eastern surf clams, cockles and quahogs, tend to be easier to purge than open-shelled clams like steamers, horseneck clams and geoducks. The worst of them all is the Western bent-nosed clam, which lives in dense mud and can take days to purge.

Adding corn meal to the purging water does nothing. There, I said it. Think about the biology of a clam for a moment to understand why. Clams are filter feeders. The reason they have sand and grit in them is because they live buried in sand or mud. This proximity to grit naturally gets the stuff into the clams, which filter with their shells partially open — which is how the sand or mud gets in. Clams filter microscopic particles, not stones or grains of sand — or corn meal. Clams don’t have gizzards. They don’t need grit to do their jobs. Grit in your shell is just a side effect of being a clam.

The myth is that corn meal somehow causes a clam to “cough up” more grit than it normally would, or that the clam “eats” the corn meal and spits out grit. Well, to test that I did an experiment:

  • First, I let 50 Western littleneck clams purge themselves for 18 hours in seawater. They expelled about 47 grams of grit (weighed after drying) after about 18 hours.
  • Next, I added exactly 150 grams of coarse corn meal to the purging water and let another 50 Western littleneck clams purge themselves for 18 hours. After that, I carefully removed the clams, poured off the water and spread the corn meal out on a baking sheet to dry completely. Then I weighed it again. The corn meal plus grit weighed 196 grams. You would think that if clams had “eaten” the cornmeal, there would be a decrease in the dry weight of the meal after 18 hours, no?

If you were to bury clams in cornmeal, yes, some would get inside them the way sand does in the wild. But why bother?

Purging clams is mostly a function of time, with oxygen and temperature as ancillary factors.

The single most important ingredient you need to purge your clams of grit is seawater. This is not so hard to obtain if you are getting your own clams. Bring a 5-gallon bucket and fill it 2/3 of the way up with seawater as you leave the clamming grounds. Armed with this, you can purge virtually any clam. Oh, by the way, you cannot purge a clam in fresh water. Fresh water kills clams. And dead clams are, with few exceptions, no good to eat.

Why is bringing home seawater so important? Because clams live at different salinity levels. The average salinity of the ocean is 35 parts of salt per 1000, but in some wide, shallow clam beds the salinity climbs far higher through evaporation. In other beds, the salinity is lower because the clams are near an estuary where fresh water flows. If you bring seawater from where you dug the clams, you need not guess at how salty your soaking water should be.

Hank Shaw, digging a clam

If for some reason you forgot to bring back seawater, you can recreate it decently by remembering that 35 parts per thousand ratio. Go buy sea salt — actual sea salt, not rock salt, not iodized salt — and dissolve 35 grams of it (about 2 tablespoons plus another teaspoon) into each 1000 grams of non-chlorinated water, which is about 1 liter. You’ll need enough to submerge your clams.

If you want to get fancier, you can use a hydrometer, which measures water density. Where I do a lot of my clamming in Tomales Bay, the average salinity would read 1.024 in terms of specific gravity. This equated to 1/3 cup finely cut sea salt to a half-gallon of non-chlorinated water. Chlorine, needless to say, is not good for living things. What’s your area’s normal salinity? Google it. I bet some scientist somewhere has measured the salinity where you dig clams and put it online.

Temperature matters. Shock kills clams. Put clams living in 75°F water into the fridge and they will not be happy — and open-shelled clams will die. The reverse is also true.

Carry your clams home in your seawater and they’ll be fine. They will acclimate to the changing temperature as you drive home. If it’s really hot or cold out, put everything in a cooler. Keep in mind that clams are capable of filter feeding at temperatures as low as 34.5°F and as high as at least 78°F, which is realistically as warm as you will get in a normal indoor room.

If you’re clamming in winter, where the water is cold, go ahead and do your purge sand from clams in the fridge. But if it’s summer, keep your clams at room temperature, or, ideally, a place a bit colder, like a basement.

How long? Even an hour will help. But you can purge your clams as long as there is oxygen in your seawater. Leave your clams too long, and they suffocate and die. Overnight is what I normally do with a 50-clam limit of Western littlenecks and 4 to 10 horseneck or Washington clams. I submerge the clams by about 1 1/2 to 3 inches of seawater and cover the container they’re in — clams spit water, so you don’t want them sprinkling the inside of your fridge or basement.

purging clams, with expelled grit in the water
Photo by Hank Shaw

So, to sum up, this is how I purge sand from clams:

  • When you are done digging, fill a large bucket full of seawater to take home. Put your clams in it for the drive. If the temperature is very different between the water and your car, put everything in a cooler.
  • At home, quickly wash every clam under cold tap water to remove mud or grit on the outside of the shell. Put the clams into a large non-reactive container (galvanized steel will kill them, for example). I use a big Tupperware-style container.
  • Either let the seawater you brought home settle for 20 minutes or so, or filter it through a paper towel. You want it as grit-free as possible. Pour the water over the clams, covering by 1 to 3 inches. If you are purging especially muddy clams, hold back any remaining seawater — you’ll need to change it in a day.
  • Set the clams in the fridge, at room temperature or in a cool place — somewhere where the temperature is reasonably close to the water they were in — and leave for at least an hour, and up to 20 hours. Check on them once in a while: Most of them should have their siphons out. You will see a lot of icky stuff all over the bottom of the container. Repeat this process for especially muddy clams.
  • When you are ready, rinse the clams again. Hard-shelled clams can go into the fridge. Open-shelled clams need to be eaten or shucked.

There you have it. Now you are ready for some tasty clam recipes!

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About Hank Shaw

Hey there. Welcome to Hunter Angler Gardener Cook, the internet’s largest source of recipes and know-how for wild foods. I am a chef, author, and yes, hunter, angler, gardener, forager and cook. Follow me on Instagram and on Facebook.

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95 Comments

  1. Soaked up to two hours in heavily-salted water (i’m nowhere near any ocean!). Rinsed, repeat, rinse again.

    Clams still gritty! So discouraging!

  2. Funny how many often I end up on this site when searching for cooking and prep info and recipes. I’ve always added pepper in the water to encourage clams to spit out their sand – perhaps some experimentation is in order. Thanks for the tips, definitely learned a few things as usual!

  3. Hank, I own a small seafood market near Scranton PA at least 2.5 hrs from the Atlantic coastline. I want to provide degritted/ purged clams to my customers but I can’t find a system to clean large quantities of clams. Right know I sell about 3,000 clams a week. do you know of any larger systems and can I effectively treat freshwater with sea salt to achieve the oceans/bays salinity? Also, after the clams are purged, does that reduce their shellfish.

  4. Too salty: boil clams ONLY long enough to open; then remove from shell.
    Give a final rinse in fresh water before adding to recipe.
    Also, only add at the very end; as the longer you cook em the chewier the clams get.
    Use fresh grated Parmesan instead of craft or any other plastic-bottled park.
    Unsalted butter in your recipes may also be a good choice.

    Hope this helps 🙂

    1. Patrick: Um… that’s all fine for cooked recipes, but this is for on the half shell. I agree with you on freshly grated cheese, although I rarely use cheese with seafood. And I never use salted butter.

  5. I went clamming, dug a peck of clams, brought home 3 gallons of seawater to purge the clams (normally I use fresh water with corn meal, but have been dissatisfied with the amount of sand left in the clams). I made stuffed quahog and clam pesto. Both recipes turned out too salty. I did not add any salt. Only thing I can think of is the salty sea water used to purge the clams instead of the fresh water and cornmeal. On the positive side, there was much less sand in the clams.

    1. Robert: Fresh water kills clams. If you purge using it, they will close up tight as long as they can, then die. So if you’ve had success before, it’s because you pulled the clams before they died. Sorry it was too salty for you. Maybe scale back the parmesan for the pesto, as it’s salty, too. Stuffies should be salty — what crackers did you use with them? Saltines and Ritz are both salty.

  6. The best (andI mean the absolute best) crab cakes I ever had was at the Biltmore Estate Hotel in Asheville, NC. Here’s the recipe (and the Tartar Sauce to go with it)
    Biltmore Estate Carolina Crab Cakes
    2 Pounds Crab Meat
    2 Eggs
    1/4 Cup Panko Bread Crumbs (Japanese Style Bread Crumbs)
    2 Tablespoons Minced Chives
    Freshly Squeezed Juice of 1/2 Lemon
    1/2 Teaspoon Freshly Grated Lemon Zest
    1/3 Cup Mayonnaise
    1 and 1/2 Tablespoons Dijon Mustard
    1 and 1/2 Tablespoons Whole Grain Dijon Mustard
    1 Tablespoon Old Bay Seasoning
    Kosher Salt
    Freshly Ground Black Pepper
    2 Tablespoons Olive Oil or Unsalted Butter
    Preheat oven to 325 degrees Fahrenheit. Pick through the crab meat to remove any bits of shell. Combine with eggs, bread crumbs, and chives in a medium bowl. Add the lemon juice, mayonnaise, Dijon mustard, whole grain mustard, Old Bay seasoning, salt, and pepper; mix well with a wood spoon or gloved hands. Shape tightly into balls and flatten gently to form cakes, placing on a baking parchment lined pan sprinkled with additional bread crumbs.
    Heat a medium skillet over medium heat and add the olive oil. Add the crab cakes in batches of 4 or 5 and cook until golden brown on the bottom. Turn the cakes and cook for one minute longer. Remove to a baking pan lined with parchment. Bake for 15 minutes or until cooked through.

    Tartar Sauce
    1 Egg
    1 Tablespoon Garlic, Grated and Made Into a Paste
    2 Tablespoons Freshly Squeezed Lemon Juice
    1 Tablespoon Freshly Grated Lemon Zest
    1 Tablespoon Chopped Fresh Flat Leaf Italian Parsley Leaves
    1 Tablespoon Capers
    2 Tablespoons Chopped Scallions
    1 Cup Olive Oil
    1 tablespoon Creole or Whole Grain Mustard
    1 Teaspoon Kosher Salt
    1/4 Teaspoon Cayenne Pepper
    Nick

  7. This is a nice article Hank and thank you for writing it.
    Today we are eating Bean clams. I’ll be extracting the nectar and filtering it through a coffee filter. Then I’ll boil the remains in salt water until the meats float.
    Add it together with ginger, garlic, tomatoes and butter and serve over JASMINE rice.
    Jasmine rice is a superior white rice.

    Poor poor math skills and reading comprehension amongst some of the commenters.

  8. Hi Hank,

    thanks a lot for the speedy response! We’ve purged them for about 16 hours now, refreshing the salt water three times, but the water still got pretty muddy. So we might let them sit till tonight (already had to buy new salt).
    Thanks again!

  9. Hi Hank,
    we just had our first foraged cockles (picked from a nice English beach 🙂 We cooked the first batch of slightly smaller ones after having purged them in salt water for about two hours. Quite a few were still a bit sandy. Now we’re wondering if we can leave the bigger ones in over night? We took them out of the first batch of water to separate the smaller ones and then put them back in new salt water. But leaving them till tomorrow would mean about 14 hours in water. Will they survive? Don’t wanna ruin them. Thanks for the great website!
    Viv

    1. Viviane: I always leave my clams for at least 12 hours in saltwater, so they will be fine. Just left some western littlenecks, which are a sort of cockle, for three days in saltwater in the fridge. They were fine.

  10. Hi Hank, I live in Point Arena and I am wondering if there is a map of clamming places or could you point? I am obviously a novice and have not a clue. Trying to learn

    1. Lisa: No idea, but I know your areas are excellent for clams. Start by just looking around your local beaches at low tide. You want protected places, not rocky areas with open surf from the Pacific. Bays, inlets, that sort of thing.

  11. Good words for once, I’ve had some bad purges in my time, your words make sense. I’ve been at one spot in the UK for five years now seeing the changes is interesting. Less Mussels, possibly due to fishermen using them as bait, over collecting. More clams today less cockles, not sure why , but the water seems warmer and there is more seaweed where the clams are. This may be hiding them from the birds? All guesses.

  12. Hi there, Hank.

    Thanks for the excellent instructions!

    I have a clam quandary: I placed a half pound of bent-nose clams in seawater in a cool corner of the kitchen yesterday evening. When I went give them fresh seawater this morning, it looks like they dropped their siphons. The bowl is littered with grit and little noodle-parts. On the other hand, they’re still closed tightly and a few are bubbling in the new seawater. Do you know what might have happened?

    1. Victoria: Huh. That’s a new one. I rarely mess with bent-nosed clams, though. I’d cook them today.

  13. Elijah,
    Where did you get gapers on the oregon coast at? Yes they will be fine on ice for a few hours as long as ice doesn’t melt causing them to sit in freshwater. Most clams do great in a large glass bowl in the fridge with a damp cloth over them for the first 24 hours

  14. hi Hank,

    I got some gapers off the Oregon coast, we knew we were gonna be busy and not go home immediately so we threw them in some ice (no water just ice). Is this OK if they’re still alive? I am going to try to mix up some salt water now that I’m home (about 4hrs later) and purge them. Thanks!

  15. Hi there. I have left my razor clams overnight in fresh water. This morning they look dead. Are they still ok to eat?

  16. Ok Hank, I have been looking every where and can not find an answer. I live in Mississippi and fish in Biloxi. I want to know if you have any idea if clams out of the Gulf of Mexico, oil spill aside, can be eaten. I believe they can, I just want one person to say yes or even that they have experience eating them and they did not taste like you were chewing bayou mud. I can’t even find info on clam limits in my area, lol.

    1. Tony: Damn. Can’t help ya. I don’t know anyone who clams in the Gulf. Surely the state Fish & Game departments have limits and seasons, right?

  17. My grandfather buy store bought clams alive but on ice and wants to keep them alive for a long time should I change the temperature of the water due to the ice

  18. Thanks for the guidance. I had put the clams in fresh water with salt, for 12 hours. Very little activity. Today I got sea water… Within 10 minutes, the water with the clams looked like a dance party! It made a huge difference. It for sure works. Cheers