Champagne glass shape for sparkling wine as materials for drinking vessels shifted from metal and ceramic to glassware. Initially, the flute was tall, conical, and slender; by the 20th century, preferences changed from a straight-sided glass to one which curved inward slightly near the lip. This inward taper is designed to retain champagne's signature carbonation by reducing the surface area for it to escape. Nucleation in a champagne glass helps form the wine's bubbles; too much surface area allows carbonation to fizzle out quickly. More bubbles create greater texture in the taster's mouth, and a flute's deep bowl allows for greater visual
Glass-to-metal seal glass, the surface has to be properly oxidized. The oxide layer has to have the right thickness; too thin oxide would not provide enough material for the glass to anchor to, too thick oxide would fail in the oxide layer, and in both cases the joint would be weak and possibly non-hermetic. To improve the bonding to glass, the oxide layer should be borated; this is achieved by e.g. dipping the hot part into a concentrated solution of borax and then heating it again for certain time. This treatment stabilizes the oxide layer by forming a thin protective layer of