Brined pickles are prepared using the traditional process of natural fermentation in a brine which makes them grow sour. The brine concentration can vary between 20 g/litre to more than 40 g/litre of salt. There is no vinegar used in the brine of naturally fermented pickled cucumbers.
The fermentation process is entirely dependent on the naturally occurring Lactobacillus bacteria that normally cover the skin of a growing cucumber. Since these are routinely removed during commercial harvesting/packing processes, traditionally prepared pickles can only be made from freshly harvested cucumbers, unless the bacteria are artificially replaced.
Typically, small cucumbers are placed in a glass or ceramic vessel or a wooden barrel, together with a variety of spices. Among those traditionally used in many recipes are garlic, horseradish, whole dill stems with umbels and green seeds, white mustard seeds, grape, oak, cherry, blackcurrant and bay laurel leaves, dried allspice fruits, and—most importantly—salt. The container is then filled with cooled, boiled water and kept under a non-airtight cover (often cloth tied on with string or a rubber band) for several weeks, depending on taste and external temperature. Traditionally stones, also sterilized by boiling, are placed on top of the cucumbers to keep them under the water. The more salt is added the more sour the cucumbers become.
Since they are produced without vinegar, a film of bacteria forms on the top, but this does not indicate they have spoiled, and the film is simply removed. They do not, however, keep as long as cucumbers pickled with vinegar, and usually must be refrigerated. Some commercial manufacturers add vinegar as a preservative.