How to Make Salt From Local Seawater

Capture an abundance of the sea’s briny, bitter and butter-sweet trace minerals with these experimental techniques for how to make salt from local seawater.

How to Make Salt

The process proved surprisingly easy, and the yield was much higher than we had expected. And our salt looked pretty (pure white), smelled fresh, tasted exactly like the ocean, and made a fine seasoning for our feast.

Photo By Thomas J. Story (c) 2011

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Based on the James-Beard-Award-winning One-Block Diet, The One-Block Feast (Ten Speed Press, 2011) is the ultimate guide to eating local. Complete with seasonal garden plans, menus, 100 recipes and 15 food projects, this guide explains how to raise and produce everything needed for totally made-from-scratch meals, all from your own backyard. The following excerpt on how to make salt is taken from “The Winter Projects.” 

You can purchase this book from the GRIT store: The One-Block Feast.

How to Make Salt

Of all the projects we attempted as part of our One-Block feasts, this may have been the most far-fetched. We had read of other people’s efforts, most memorably Michael Pollan’s in The Omnivore’s Dilemma, in which he scavenges water from trash-strewn wetlands and evaporates it on his stove top into brown salt that, he writes, “tasted so metallic and so much like chemicals that it actually made me gag.”

But we persisted because we knew we had to have seasoning for our dinner, and figured—what with the San Francisco Bay to one side of us (the same bay that Pollan harvested, actually) and the Pacific Ocean on the other, we had some water to choose from. Also, the other raw materials that we had “imported” for our feast—grapes for the wine, olives for the oil, and milk for the cheese—at least were transformed from their natural state by our own hands. It would be copping out to just go buy salt.

The process proved surprisingly easy, and the yield was much higher than we had expected. And our salt looked pretty (pure white), smelled fresh, tasted exactly like the ocean, and made a fine seasoning for our feast. As to whether it was safe to consume or would behave like normal salt in cooking, we weren’t sure. We were just happy that we had, in fact, made our own salt from local seawater.

Pacific Sea Salt 

We hauled drums filled with Pacific seawater to our Menlo Park offices and reduced several gallons to salt.

How to Make Salt: What to Use

Food-grade plastic drums. We had a few clean 5-gallon food-grade plastic drums left over from making olive oil, so we used them to transport the brine. Any thoroughly washed bucket will do. Drums cost about $15 each, plus $20 handling fee if your order is less than $100, at The Olive Oil Source (805/688-1014).

Coffee filters or a triple layer of cheesecloth. For filtering the water. About $4.50 for 2 square yards at a hardware store or cookware store.

Pyrex liquid-measuring cups. To measure the hot brine.

Stockpot. For boiling the brine. From $60 online or at a cookware shop.

Two Pyrex 9 by 13 inch baking dishes. For baking and evaporating the brine. About $7 each at a cookware shop.

Rigid metal spatula. Once the salt crystals have formed, you have to scrape them off the pan.

How to Make Salt: Get Started

1. Collect seawater. After thinking about the nearest cleanest portion of the ocean, we settled on Bean Hollow State Beach near Pescadero, since no streams (which can carry toxins and other runoff) flow into the ocean there. We collected 40 gallons of the chilly Pacific in our plastic drums. Another time, we collected seawater near Fort Bragg, a small coastal town north of San Francisco. Both batches were processed the same way.

2. Filter. Back at the office, we poured a test batch of water through a coffee filter (or layered cheesecloth) into the stockpot.

3. Boil. We brought the filtered water to a rolling boil and held it there for 20 minutes to kill any noxious bacteria. We were aware that this would have no effect on other toxins or heavy metals. In fact, if they were present, the cooking might concentrate them.

4. Filter again. To remove any remaining particles, we filtered the water again, this time into heat-proof measuring cups.

5. Bake. The first time we made salt, we used aluminum baking sheets, which gave us a large yield—but the salt was grayish and tasted like aluminum. We then switched to Pyrex baking dishes and got salt as white as snow with no funny taste. Here’s how: We poured the filtered water in 3-cup batches into the pans, then baked it in a 350°F oven for about 21/2 hours, checking often toward the end to make sure we didn’t burn the crystals as they formed.

Sun evaporation as an alternative. Feeling sheepish about the fossil fuel consumed by baking, we also tried putting the brine-filled baking sheets outside to evaporate in the sun. This didn’t work very well, owing to spotty weather and to lots of leaves and other debris blowing into the exposed salt. We tried again, covering the pans with cheesecloth, and after several days, we had salt. The yield was much lower than what we got with the baking method, however.

Or stovetop boiling. Another early attempt involved boiling filtered seawater until the liquid completely evaporated and salt lined the inside and bottom of the pan. This ended with a steamy kitchen and burning hot crystals of salt flying out of the pot like popcorn and hitting us on the arms. Plus, boiling down all that water and then running the fan to cool off the kitchen wasn’t energy efficient, so baking became the best choice.

6. Scrape. At the end of baking, the crystals rimmed the pan, and we scraped them off with the metal spatula. The yield varied depending on the source of the brine: We got about 2 tablespoons good-tasting, snowy white salt from 3 cups brine collected at Pescadero. The same amount of brine from Fort Bragg yielded between 1/3 and 1/2 cup.

7. Taste. We sent a sample of our Fort Bragg salt to salt expert Mark Bitterman, owner of the specialty shop The Meadow in Portland, Oregon. Here’s what he said: “[It] has a lovely opaque, crème fraîche color that comes from an abundance of the sea’s trace minerals. The crystals are marvelously diverse in form, ranging from finely fringed micro-grains to layers of laminated flakes. And the flavor: a roiling oceanic assault on the senses—only nice, like being caught in a wave of sun-warmed water, briny and bitter and butter-sweet.” He further pointed out that, unlike commercial salt manufacturers, we had reduced all the available salts in our brine, each of which has a different salinity and flavor. The big guys tend to go for sodium chloride only, which provides most of the salt and precipitates first, because it is more efficient. “What you guys have done is grab it all, including the calcium and magnesium salts. You’ve got a big dynamo of saltiness. It has everything in it.” This, it seems, is the hallmark of artisanal salts. We are artisans!

8. Test. We spent some fruitless time contacting various clean-water agencies to ask about getting our water samples tested. One officer, with a branch of the Environmental Protection Agency, said to us, “Why would anyone want to drink salt water?” He had a point. So we moved on to the salt itself.

We then considered sending a salt sample to a food lab, but a heavy-metals screening would have cost $275 for each possible contaminant (and there are many), and a test for pesticides at least $100. Kind of pricey for seasoning, we thought. As Bitterman pointed out, salt is extremely dilute in the ocean—and is not a bioaccumulator of toxins—so the chances of it containing large amounts of bad stuff are probably not all that high. At this point, we are happy to have produced salt that tastes good and, we hope, might be harmless.

Helpful Information

Salt is a fascinating subject. It has roughly fourteen thousand applications, from de-icing roads to food preservation, and was so valued in Roman times that soldiers were paid wages in it.


Neptune’s Gift: A History of Common Salt, by Robert P. Multhauf (Johns Hopkins University Press, 1978).

Salt: A World History, by Mark Kurlansky (Penguin Books, 2002).

Salted: A Manifesto on the World’s Most Essential Mineral, with Recipes, by Mark Bitterman (Ten Speed Press, 2010).

Other Resources 

How to Make Salt from Sea-Water, by John Leconte (Governor and Council of South Carolina, 1862). An oddly engrossing pamphlet written at the request of the state’s governor by a chemistry and physics professor at South Carolina College. At a time when the oceans were cleaner than they are today, Leconte spells out how to boil down seawater in 20-foot sheet-iron pans over wood fires. You’ll find yourself engrossed in the details of sludging and soccage (crystallization).

The Salt Institute, an association of salt producers, puts forth all sorts of information about salt on its Web site—everything from stats on world production (China leads) to solution mining to nutrition.

More One-Block Feast Winter Homesteading Ideas:

How to Make Mead, the Honey Wine
How to Make Escargot From Your Own Garden Snails
15 Healthy Winter Recipes
Preparing a Local Winter Feast
One-Block Feast: Guide to Winter Garden Vegetables 

Reprinted with permission from The One-Block Feast: An Adventure in Food from Yard to Table by Margo True & the staff of Sunset Magazine, copyright © 2011. Published by Ten Speed Press, a division of Random House, Inc. Buy this book from our store: The One-Block Feast.