An overly salty soup is no one's idea of a good meal, and this comes from a self-professed salt fiend! Here are two tricks to get the seasoning just right...and what to do when you realize you were maybe still a bit too heavy-handed.
Think about salting at the beginning and the end. The first step of almost any soup is to sauté the vegetables to bring out their flavor and get them started cooking. Adding salt at this stage ensures that the vegetables themselves are seasoned properly. They absorb salt and get tasty. A teaspoon of salt for several cups of chopped vegetables will do the trick.
When you add the broth and get the soup simmering, the soup will at first taste under-salted. Remember that the soup is going to reduce a little as it simmers so resist the temptation to add more salt at this point.
A few minutes before you're ready to take the soup off the heat, taste it again and add more salt as needed. With my soups, I find that another teaspoon or so is usually needed to brighten the flavors and bring the soup together. Now when you serve the soup, the seasonings will be just right.
If your soup still ends up tasting a little salty, first try adding a few more cups of broth or water. This will thin out your soup - and the salt. You can eat it like this, or you can add a potato or two to absorb some of the extra liquid (and, yes, its salt!). A cup of rice or some pasta will accomplish the same end.
Any other tricks for avoiding an over-salted soup or adjusting for it post-facto?
Related: Quick Tip: Make Cheese Rind Stock!
(Images: Emma Christensen and Ribollita Soup - Stephanie Barlow)
TW Salt Mill by Wil...

Most importantly, don't give measurements of salt by volume! Use weight instead. If you must give it by volume at least specify what type of salt you are using. A teaspoon of table salt is different from a teaspoon of Morton's kosher salt is different from a teaspoon of Diamond kosher salt. If you are using Diamond kosher salt and the reader is using table salt, they might be adding three times as much salt as you!
I think I read an article where they debunked the idea that a a potato added to soup would absorb the salt or make the final product less salty.
I've heard the potato method doesn't work. I have tried honey because I accidentally put 2 tablespoons of salt instead of teaspoons in chili. I had to use a lot of honey but it really did work and you couldn't taste it.
I just had this problem recently and didn't know how to solve it. Thanks for the timely advice!
The honey or the salt.
I just did this last night, I just added more water and added a little more of the other seasonings it was fine. Made more soup :)
Or try vinegar.
I only salt at the end and I don't measure, I taste, adding a little at a time until I'm satisfied.
I generally cook my soups for a long time (simmering gently on the back burner) and sometimes they reduce more than I'd like, so I only ever add salt at the end, just to be safe. And I usually err on the side of undersalting and then put the salt shaker on the table and let people salt to taste.
I never use a measuring spoon to add salt when I cook. I add pinches and taste as I go. Much less likely to oversalt than when adding a teaspoon all in one go.
I'm with Runemistress. I've heard that the potato method has been found to be just as effective as simply draining that much liquid out of the soup. It really just acts like a sponge, soaking up all liquid.
Edit: I take back my comment after reading the "Add a potato or two" post. The author is indeed saying that you're just adding ingredients to dilute the soup, not using the potatoes to soak up salt.
"I love potatoes as much as the next guy, but they are not magical—and certainly not capable of selectively sucking the salt out of your soup."
http://cookingquestions.myrecipes.com/2010/11/how-do-i-fix-a-dish-with-too-much-saltdoes-adding-a-potato-work-.html