Glass lovers will occasionally stumble over the term “optical glass” or “optically blown glass.” Admittedly, the term is misleading and ambiguous, because optically pure glass, e.g. for lenses or eyeglass lenses, is also referred to as optically pure glass. In traditional glass factories, the term is known as a special type of finishing and refining that already takes place in the glassworks.
The beginning of glass production is as always, a small but very precise glass bulb is blown, that is the “Kölbel” This small glass bubble is then adjusted to approximately the later size by further glass extractions from the melt. Then comes the trick: The hot and still malleable glass bubble is pressed into an iron mould and inflated tightly. The iron form has a pattern on the inside that is pressed into the wall of the glass. One can imagine the iron form to look like an “iron maiden.”
Then the glass, which is now provided with the pressed “optical” pattern, is blown as usual in the wooden glass form.
The pattern in the glass is now mainly noticeable on the inner wall of the glass, on the outside it is relatively smooth. Thanks to this special finishing, the glasses are given uniform wave-shaped structures, which have a special effect. In contrast to a finishing by a later grinding, the optical patterns always seem a little washed out.
This kind of refining of glass or crystal looks especially beautiful on simple but well designed shapes.
These techniques of glass making and processing have been around for hundreds of years. We are happy that there are still glassworks that produce such extraordinary glass for us.
Our Maria, Amelie and Stella series thus retain their characteristic glass structure.
Joh. Oertel & Co.
Petra M. Schütte
P.S. next time: handles and stems