Ancient glassmakers discovered a technique called core forming. A core was formed from dung and clay, then dried. The core was covered with glass. After cooling, the core was scraped out. The bottles were used for perfume and cosmetics.
The technique of forming a vessel by winding or gathering molten glass around a core supported by a rod. After forming, the object is removed from the rod and annealed. After annealing, the core is removed by scraping.