Size Makes a Difference

Reader Emily makes a great point: trace impurities may not have much impact on the way a salt tastes, but the size and shape of the salt crystals definitely do. Very true. And again, that’s not because the salt is any different chemically, but because crystals of varying sizes and shapes have different surface areas, and so dissolve at different rates.

Salt grains come in two basic shapes: granules and flakes. Granules are the shape we’re all used to, the little perfect cubes we all know as “table salt”. If you remember from other discussions on the subject of crystals (fat crystals, starch crystals, ice crystals), crystallization is what happens when molecules of the same type start stacking up upon one another. Given that molecules of sodium chloride are cubical, it’s easy to see why they might naturally want to stack up into cube shapes. In fact, given the right conditions, salt can grow into huge cubical crystals known as halite, which can be anything up to 4 or 5 inches across.

But notice I said given the right conditions, for in order for salt to crystallize into cube-like shapes, the salt water brine that creates them must be very pure and heavily saturated (far more so than sea water). Also, the crystallization must happen fairly quickly. Modern table salt manufacturers achieve the right conditions by using a purified brine (pumped out of flooded underground salt deposits) which is then evaporated in a special vacuum chamber. Without all that groovy gear, everyday table salt would not have anything like its current uniformity.

Which brings us to “flake” salt. Flake salt, as the name implies, is fairly flat in shape. Salt makers achieve the shape either by crushing cube-shaped granules with heavy rollers (Kosher salt), or by allowing fairly impure brine to crystallize randomly. Flakes form because impurities get between the gathering salt molecules, preventing them from forming uniform crystal shapes. Such random shapes are typical of salts that are allowed to crystallize naturally in ocean-side evaporation ponds.

Depending on where the ponds are, how the brine is allowed to evaporate, how the salt is harvested, and whether or not it’s washed and/or processed, the flakes can vary significantly. So can our experience of them. Large, flat flakes dissolve almost instantly on the tongue, while smaller, thicker granules dissolve much more slowly (notice I say “dissolve” and not “melt”, since the true melting point of salt is somewhere around 1500 degrees Fahrenheit). Sellers of flake salt can thus achieve a variety of effects by selecting for flakes of different sizes.

But again, this “variety” of flavor only holds so long as the flakes don’t dissolve, which is why an expensive salt like fleur de sel should only be used as a condiment. Add gourmet salt to anything that’s more than a little wet and/or warm, and your $20-a-pound luxury item becomes plain old NaCl again. And that puts us right back to where we started.

13 thoughts on “Size Makes a Difference”

  1. You casually say “washed salt”, but it is usually only after a do-it yourself session that people wonder how exactly they do it without the salt going down the drain… Why you use saturated water and don’t discard it often 🙂

    upT

  2. And it’s this variation in size and shape that leads to the crucial difference between salts in baking. Fluffy flakes of salt fill a teaspoon with less weight than grains. So a teaspoon of kosher is NOT the same as a teaspoon of table salt. You can get around this by measuring by weight, but unless your scale goes down to decigrams, it’s just as accurate to use a teaspoon volume measure. The best thing you can do in baking and candy making is to use table salt unless the recipe specifically calls for a different salt.

    1. Bleh, some chunks got accidentally deleted here.

      “You can get around this by measuring by weight, but because salt is so light, unless your scale goes down to decigrams, it’s just as accurate to use a teaspoon volume measure.”

      For comparing volume measure to weight measure between the same kind of salt, that is. Sorry, I hadn’t finished my coffee when I wrote my first comment.

      1. Thanks Geek Lady, and you’re so right! Measuring salt by volume can be dangerous if you change your particle sizes regularly. It’s why I’d never recommend any large-particle salt for anything other than a garnish!

        Cheers,

        – Joe

        1. I have one cookie recipe where I was playing around and kosher was all I had available. And since those cookies came out perfect, I don’t dare change anything. Dark chocolate & espresso, with just the right amount of salt to boost the chocolate. But that’s the only baking I do that uses anything but table.

          1. I don’t blame you. And those big chunks of salt can be awfully nice…a big salty explosion on an otherwise bland device. I’ love large crystal salts in the right application!

            – Joe

    1. I toned it down after I got criticism over my “Wish I Had a Bigger Sausage” post from a few weeks back. Actually, now I do have a bigger sausage — and I plan to make sausage in brioche again this weekend!

      Cheers,

      – Joe

  3. For a take on a different aspect of salt, I recommend Salt: A World History by Mark Kurlansky. Although I found some parts of it a bit of a stretch, overall I really enjoyed it.

    1. It’s a good book, I agree. His Cod book is fun as well. Thanks, Sherry!

      – Joe

  4. My brain is pretty much in the gutter so I liked your mild hint of size matters.
    Another fabulous book re: salt— Salted: A Manifesto on the World’s Most Essential Mineral. I was fortunate to attend a tasting by the author, Mark Bitterman. (Book includes recipes.) He explains distinct flavor differences between salts. As you mention– “artisan” salts should only be used as finishing salts. Mark would agree completely.

    1. Thanks Letty!

      I appreciate the comment and like your site very much!

      Cheers,

      – Joe

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