The reason why glass products have seam lines?

The appearance of stitching lines in glass products is caused by differences in the production process. Some glass cups are produced using molds, so there may be seams, while ordinary mechanical glass cups are made by dividing the glass product into two halves and then assembling them together. The seams are subjected to high-temperature treatment to blend them together. In addition, some glass cups have seams in the middle, which are usually caused by the joints between different glass cups during the production process.