This mold-blown Bottle with Spiral Decoration has a globular shape, with a flattened, slightly hollow shoulder. The cylindrical neck is provided with a thick mouth. The disk-shaped base gives the bottle stability, but shows a strongly concave pontil mark (a pontil mark is a sort of scar left on the base of a bottle by the rod that holds the container during the blowing process).
The decoration combines both molding and blowing techniques: the parison (mass of molten glass) was first poured into a mold adorned with vertical ribs, and was then blown. The counterclockwise spiral incisions were obtained by slightly rotating the bottle. Finally, the vessel was placed back into the same mold, so as to form the final criss-cross pattern with a myriad of small granules in relief.
This beautiful vessel, embellished by its bluish color and elaborate decoration, belongs to a class of bottles that generally come from the central or eastern Iranian world. They exist in various sizes, globular or cylindrical, with a complex or more linear pattern: our example is remarkable for its sturdiness and its size, certainly above average.
Such bottles would have been used for the storing and transport of liquids, as also attested by their rather robust appearance. Chronologically, they can be dated to the Islamic period, between the 10th and the 11th century A.D.