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 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, 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 placing 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 as the stems
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