In New England, the dead of winter doesn’t present many foraging opportunities. I’ve managed, with local assistance, to grub up some chives, bay leaves, and wintergreen, but that’s about it. There is one substance, though, necessary to human life, that we have in abundance here on Cape Cod: salt. We have it in huge quantities, all around us, there for the taking. The only problem is that it’s dissolved in water.
To get at the salt, you have to evaporate the water, a process that requires energy. Since energy is expensive and salt is cheap, this is usually a losing proposition. In the summer, you can employ the sun, but I’m looking for forageable items now, when it happens to be winter. I figured I’d have to put salt on the proverbial back burner until at least June, because if I put it on the literal back burner in February it would be the most expensive sea salt known to man.
Then the light bulb went on. We heat our house primarily with wood and, like just about everyone who heats with wood, we humidify the house by filling a cast-iron pot, designed for the purpose, with water and leaving it on top of the stove. In other words, we’re already in the evaporation business. Why not simply use sea water, and harvest the salt when the water’s gone? Genius!
Kevin wasn’t sold. “So we drive to the ocean, schlep the water back here, store it in the house, keep filling the pot with it, and end up with, what, three tablespoons of salt, retail value seven cents?”
“I think it’ll be more than that,” I said, with more confidence than I felt. How much salt is in sea water, anyway?
How did we answer those kinds of questions before the Internet? Turns out sea water is about 3.5% salt by weight, which means that each liter of sea water should yield 35 grams of it, about an ounce and a quarter. So a gallon should get us at least four to five ounces, a significant haul.
Kevin didn’t believe it. “I don’t believe it,” he said. But he was encouraged enough to participate in the enterprise.
In order to get the salt out of the water, you first have to get the water out of the ocean. To do that, I donned my waders and Kevin and I put our largest manageable container – a four-gallon stainless steel stockpot – in the back of the truck. We headed out to Sandy Neck. Fortunately, it was a cold day, and there were only a couple of people there to watch me wade into the surf, pot in hand, and attempt to get four gallons of water in it while getting none down my waders. The attempt gave “catch a wave” a whole new meaning.
After several inept swoops that bagged a cup or so of water and several pounds of sand, I finally caught a wave in the sweet spot and filled the pot.
I am not at all sure this is legal. I suspect there is a statute somewhere on the Massachusetts books that says that you’re not allowed to remove anything from the Commonwealth’s beaches – no water, no sand, no flotsam, no jetsam. But nobody stopped us, and we took our pilfered water home to evaporate.
To maximize evaporation you want to maximize surface area, and we thought the best vessel for this experiment would be our Le Creuset cast-iron roasting pan. The iron would retain heat, and the 10’x14′ surface would turn our water to salt relatively quickly. We poured the water through a coffee filter to remove at least some of the impurities and critters, and filled the pan.
Watching water evaporate should be exactly as exciting as watching paint dry, so I can’t account for the time Kevin and I spent standing around the stove, staring at the water, waiting for the salt to materialize. When the level went down, we refilled it, and watched some more. Again, thanks to the Internet, I knew that water will dissolve 38% of its weight, about ten times more salt than is in sea water. Ergo, when our sea water evaporated down to about a tenth of its volume, I expected the salt to start precipitating out.
You will be happy to hear that the immutable principles of chemistry worked as expected, and when we were down to our last quart and half of water we began to see a thin film of salt form on the surface. That’s when the excitement really reached fever pitch!
The water continued to evaporate, and we started pushing the salt to the edges of the pan. Within twenty-four hours of the formation of the first crystals, we had a pan full of beautiful, snowy-white sea salt. It was just over a pound, which translates to – surprise! – 35 grams per liter.
Kevin is now a believer, and we’re going back to Sandy Neck for another batch; we’ve still got another couple months of wood-stove weather. Come spring, though, we’ll have to be content with watching paint dry.