Negative printing on fabric and its coloring with indigo reduction is also a Ticino tradition. This traditional process is widespread all over the world and in Europe it is, or was practiced, especially in the northern and eastern regions. In southern countries it is almost totally unknown (rare cases are found in France and Spain). As for Switzerland, this type of printing is not known except for some remote areas of the Valais. Ticino is today the southernmost outpost where this technique has been widespread for centuries and is currently used and known by few. The fabric in linen or hemp as well as silk, after finishing and shaping is reserved or printed in positive with carved wooden modules (often pear wood) and covered with the reserve substance, which will then protect the fabric from the indigo bath. The decoration is related over and over again with borders etc. until obtaining a complex that incorporates the decorations of the operated fabrics. Thereafter, the positively printed fabric is dried for a sufficient time so that the reserve substance adheres permanently to the fibers. Indigo is composed of molecules insoluble in water, unlike other dyes, for this reason, in order to colour it needs a chemical process, called reduction, which involves the addition of ash or other alkaline and reducers, so as to divide the molecules and dissolve them in the reduction. This becomes yellow-green thus making it possible for them to attach to the fibers of the fabric. Once the sheet is immersed in the reduction, this is exposed to oxygen and the indigo goes to oxidize: the molecule returns to the “solid” state, becoming blue and definitively adhering to the fiber. The dive is carried out several times, depending on the intensity of blue that you want to obtain. Once this process is completed, the sheet is dried again: then it is immersed in an acid solution to cancel the reserve which finally lets the color of the fabric appear, thus creating a negative decoration.