The flask is made of blown, colourless glass. The iridescence seen on the surface is due to oxidation of the glass after being buried in the ground for hundreds of years. From its shape we can conclude that it was probably a sprinkler, in other words a long-necked vessel used for sprinkling holy water. The flask was found in a dig in the area outside the basilica of Hagios Demetrios in Thessaloniki. It may have contained holy water or myrrh. It seems that the clergy used it to sprinkle and bless the faithful during services."