LaunchPad: Ancient Glassmaking—The Roman Mold-Blown Technique

In the first century A.D., glassmakers began to blow glass into molds. The technology became widely used throughout the ancient Mediterranean. This vessel came from the Syro-Palestine region, which was known for hexagonally shaped vessels. No ancient molds survived, but they were likely made of clay or metal and could consist of multiple pieces. This mold is made of three pieces, two for each side and one for the The glassmaker begins by blowing a bubble into a wad of molten glass. When the temperature is right, the glassmaker can then place it into the mold. There are patterns incised on the inside of the mold that create a raised surface on the glass. Once placed in the mold, the glassmaker blows through the blowpipe so that the molten glass expands to press into the sides of the mold. The artist must move the glass immediately to the furnace for reheating. The artist evens out the bottom of the vessel. The right temperature must be maintained for shaping the vessel, but before adding any details, the glassmaker must change the orientation of the vessel. He does this by attaching to the bottom a wad of molten glass and then breaking it from the blowpipe. Jacks are a versatile tool used to shape the mouth of the vessel. The vessel must be reheated in order to soften the glass for final shaping of the neck and lip of the jug. After finishing the neck and lip, the glassmaker uses a new wad of glass to make the handle, first attaching it to the shoulder, then quickly attaching it to the top of the neck. The glassmaker has limited time to shape the handle before the glass cools and hardens. The finished vessel will have seams where the mold pieces came together. This is one way of telling how ancient glass was made. When the vessel is finished, it needs to go to an enclosed area for cooling. Vessels are still hot to the touch and must remain in the insulated space where they can slowly cool. This method allowed for mass-produced vessels like this design marketed to early Byzantine pilgrims in Jerusalem.