At this point the second stage of transformation of the concentrated boiled grape-must takes over. Here the product undergoes a chemical and physical alteration for an indefinite period of time during which the distinctive features of the balsamic vinegar are perfected. The particular type of wood employed contributes to characterise the balsamic vinegar produced. In past centuries the number of casks making up a vinegar making set could even reach forty units, which allowed the transformations to develop harmoniously in gradual decreasing order. Nowadays a set of just ten casks is considered to be remarkable.
Decantation is part of the operations required for the correct handling of the set.
These operations require an expert hand and craftmanship with great care for the state of development of the product contained in each cask so as to ensure its best development and its being kept alive over the centuries. The art needed for decanting and handling the casks is wrapped in mystery, and mystery has always accompanied the transformation of balsamic vinegar into the characteristic and peculiar uniqueness with which it appears to any observer. The vinegar making sets are kept at home in the attic. In fact, during its development the product must be kept in an environment without moisture with permanent high temperatures in summer and with cold in winter. The summer heat favours the activity of micro-organisms, while the winter cold, instead, lets the product rest and makes its limpid.