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I found this which is one of the best explanations of salt that I've found. It does go on to rock salt and halite. We don't buy the Morton kosher salt because I don't like added chemicals in my salt. We read labels now.
Table Salt
This is by far the most widely known type of salt. It comes in two varieties; iodized and non-iodized. There is an ingredient added to it to absorb moisture so it will stay free flowing in damp weather. This non-caking agent does not dissolve in water and can cause cloudiness in whatever solution it is used if sufficiently large quantities are used. In canning it won't cause a problem since there is very little per jar. For pickling, though, it would be noticeable. If you are storing salt for this purpose, you should be sure to choose plain pickling salt, or other food grade pure salt such as kosher salt. In the iodized varieties, the iodine can cause discoloration or darkening of pickled foods so be certain not to use it for that purpose.
Canning Salt
This is pure salt and nothing, but salt. It can usually be found in the canning supplies section of most stores. This is the salt to be preferred for most food preservation or storage uses. It is generally about the same grain size as table salt.
Kosher Salt
This salt is not really, in itself, kosher, but is used in "kashering" meat to make the flesh kosher for eating. This involves first soaking the meat then rubbing it with the salt to draw out the blood which is not-kosher and is subsequently washed off along with the salt. The remaining meat is then kosher. What makes it of interest for food storage and preservation is that it is generally pure salt suitable for canning, pickling and meat curing. It is of a larger grain size than table or canning salt, and usually rolled to make the grains flaked for easier dissolving. Frequently it is slightly cheaper than canning salt and usually easier to find in urban/suburban areas.
NOTE: Not all brands of kosher salt are exactly alike. Diamond Crystal Kosher Salt is the only brand that I'm aware of that is not flaked, but still in its unaltered crystal form. The Morton brand of Coarse Kosher Salt has "yellow prussiate of soda" added to it as an anti-caking agent. Morton still recommends it for pickling and even gives a kosher dill recipe on the box so I presume that this particular anti-caking agent does not cause cloudiness in pickling solutions.
Whether flaked or in its unaltered crystal form, kosher salt takes up more volume for an eqivalent amount of mass than does canning salt. If it is important to get a very precise amount of salt in your pickling or curing recipe you may want to weigh the salt to get the correct amount.
Sea Salt
This type of salt comes in about as many different varieties as coffee and from about as many different places around the world. The "gourmet" versions can be rather expensive. In general, the types sold in grocery stores, natural food markets and gourmet shops have been purified enough to use in food. It's not suitable for food preservation, though, because the mineral content it contains (other than the sodium chloride) may cause discoloration of the food.
Solar Salt
This is also sometimes confusingly called "sea salt". It is not, however, the same thing as the sea salt found in food stores. Most importantly, it is not food grade. It's main purpose is for use in water softeners. The reason it is called "solar" and sometimes "sea salt" is that it is produced by evaporation of sea water in large ponds in various arid areas of the world. This salt type is not purified and still contains the desiccated remains of whatever aquatic life might have been trapped in it. Those organic remains might react with the proteins in the foods you are attempting to preserve and cause it to spoil.
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