This method of glass making was an early form of patterned glass and dated back to the earliest days of glass making. Basically it was blowing the molten glass into a mold that would leave a design to the glass. It was removed from the mold while still pliable and blown out to the desired size. It can be distinguished by having indentions on the inside of the glass object where the molten glass was blown into the mold. The designs are also soft and lack sharp edges as found in Pattern Glass.

Collectors in the United States generally call this early glass (before 1840) Blown Mold Glass, but it is also sometimes called Three Mold because the molds were made in 3 parts and there will be a faint line on the glass where they joined. Sometimes one will hear Pattern Glass described by the number of mold marks or lines, with the implication that 3 is better. This is a fallacy that seemingly will not die. The number of mold lines in Early American Pattern Glass is immaterial and of no significance and has no effect on value. In fact Pattern Glass manufacturers strove to eliminate any sign of lines in their wares, often advertising that their glass had been "fire polished" meaning the resulting lines were obliterated by briefly place the pressed object back in the furnace to melt them away. Often the only place mold line can be seen on Pattern Glass is in protected areas such the stems.