Page 48 - Curriculum Visions Dynamic Book

Empty mould
Tumblers
The most common forms of glassware on the table are tumblers for water or other beverages. Tumblers need to stand up to blows while being washed, yet they need to sparkle when clean. Soda lime-silicate glass is fine for this purpose, but tumblers need a shiny finish better than that used on bottles.
Tumblers are made by blowing gas into a mould. The mould is made of two halves and is lined with wetted sawdust or cork. As the glass is blown into the
mould, it causes the water in the mould liner to turn to steam. This keeps the glass from touching the mould
and so gives a smooth finish to the glass. The mould is then opened and the glass taken out
and put on a conveyor belt. At this stage it has a sharp rim. It is rounded over, or beaded,
using a flame that plays on the glass as it moves along the conveyor.
Blank ready
Blank blown
Untrimmed piece
Trimmed piece
(Above and left) Blowing is used for many containers whether they are tumblers or cathode ray tubes for computer monitors and TVs.
The glass is placed inside a mould as
a bubble of glass. Air is forced into the bubble, and it presses the glass against the inside of the mould. This is a quick and easy process for mass-produced low-value items.
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