There are various glass manufacturers and each has their formula for their colorways. The process of making their glass can be different from one another. There is machine-made glass, hand-rolled glass, and mouth-blown glass. If you have ever walked passed a Victorian house, you probably noticed how the clear glass has a slight waviness or distortion different from a picture frame glass. That is because the window used clear antique glass. Clear antique glass is mouth-blown glass. There are not many manufacturers that make mouth-blown glass due to the labor-intensive process. However, it is through this process that the glass can get that beautiful waviness, lines, or seeds of bubbles characteristic of mouth-blown glass. This also makes each sheet one of a kind and special.