Salt, and why the first step decides everything after it

Most kimchi problems get blamed on fermentation. The leaves went limp, the jar filled with water, it turned sour in four days instead of three weeks. Fermentation gets the blame because that is the part you watch. But almost all of it was decided earlier, during the step nobody photographs: salting the cabbage.

What salting is actually doing

Salting a cabbage is not seasoning it. It is removing water from it.

Salt on the outside of a leaf creates a concentration difference across the cell walls, and water moves out to meet it. A quartered napa cabbage that started rigid becomes flexible — the classic test is that a thick white rib should bend most of the way without snapping. That flexibility means enough water has left the cells for the leaf to survive being packed into a jar and sitting in its own liquid for months.

Two things follow from this. First, a cabbage that has not lost enough water will keep losing it later, in the jar, diluting the seasoning you carefully made and leaving you with a thin brine and a pale taste. Second, a cabbage that has lost too much cannot recover. It goes past flexible into slack, and no amount of good seasoning brings the texture back.

Salt is also the referee

The other job is selection. Kimchi is not fermented by adding a culture — the lactic acid bacteria are already present on the vegetables. Salt does not create them. It changes the odds by suppressing organisms that cannot tolerate a salty environment, while the lactic acid bacteria carry on more or less unbothered.

That is the whole trick. Under-salt and you have removed the referee: the competition opens up, and the things that win are not the ones you wanted. Over-salt and even the lactic acid bacteria slow down, and the jar sits there tasting of salt and not much else, taking weeks to develop anything.

This is why the vague instruction to "salt to taste" is useless here. Salt level is not a flavour preference in kimchi. It is a control on which microbes get to eat.

Weight, not volume

Coarse Korean sea salt and fine table salt occupy wildly different volumes for the same mass. A cup of one can be nearly twice the salt of a cup of the other. Any recipe that measures salt in spoons or cups without saying which salt it means is unreliable across kitchens, and this is a common reason a recipe that worked for someone else does not work for you.

Weigh it. Weigh the cabbage too. Working from a percentage of the vegetable's weight is the only way a recipe survives being handed to someone else, and it is how anyone making kimchi at any scale actually works.

The numbers, since almost nobody publishes them in English

Korean food-science work on brining is unusually specific, and it is worth knowing what the target actually is rather than guessing at "until it bends".

The conventional benchmark is a brine of roughly 10–12% salt at around 12°C for 18–20 hours. Cool and slow. Salt penetrates evenly, the leaf gives up its water without collapsing, and the rib keeps its snap.

There is also a fast method, and researchers at the World Institute of Kimchi have compared the two directly: a very concentrated brine — near saturation, around 30% — at 30°C for about four hours. In their comparison the hot, fast, high-salt method scored higher on overall taste and saltiness than the cool 12% method run overnight. Speed is not automatically the compromise it looks like.

What matters is that these are two coherent recipes, not a range to average. Brine strength, temperature and time trade against each other, and picking one number from each column gives you something that works in none of them.

Either way the destination is the same: finished kimchi lands somewhere around 2–3% salt, which is where the lactic acid bacteria are comfortable and most of their competition is not.

Traditional practice uses 천일염, coarse solar sea salt, often aged for a year or more so that residual bitterness leaches out. If you can get it, use it. If you cannot, any pure salt without added iodine or anti-caking agents will do the job — those additives can affect both colour and flavour, and there is no reason to invite the variable.

The rinse is part of the method

After salting, the cabbage is rinsed. This is not undoing the work — the water has already left the cells and does not come back. Rinsing removes surface salt that would otherwise push the finished jar far past where you aimed.

How thoroughly you rinse is one of the real household variables, and it is where two cooks following the same written recipe diverge most. A grandmother who rinses three times and one who rinses once are making measurably different kimchi from identical instructions.

Then, and only then, drain

Cabbage that goes into seasoning still dripping will dilute it. Let it drain properly — long enough that the last of it comes off in drops rather than a stream.

None of this is the interesting part of making kimchi. It is, however, the part that determines whether the interesting part goes well.