Back in 2004, China began construction on a modern glass factory in the port city of Nampho. The factory is located just off the Taedong river and was formally opened on October 9th, 2005. The Dear Leader Kim Jong-il and the visiting Vice Premier Wu Yi from China attended the opening ceremony, with glass production beginning in 2006.
This is one of the two main rooms with conveyors that help move the glass through the factory. Quite interesting visiting one of these industrial factories, much less in the DPRK! I don't know the full process, but as the glass goes through the different stages, imperfect glass is destroyed, falling down below. I have no idea what a normal defect rate should be, but I heard and saw a lot of glass breaking.