Stoppering

Stoppering is the act of inserting a stopper—a plug or closure—into the opening of a container, instrument, or apparatus to seal it. Stoppering serves to prevent evaporation, contamination, and gas exchange, preserve contents, maintain sterility, and regulate environmental conditions inside the vessel. It is used across laboratories, pharmacology, wine production, and chemical manufacturing.

Common stopper materials include natural cork, rubber, silicone, neoprene, and glass. Cork is traditional for wine and some beverages but can cause taint (TCA) and varies in tightness; synthetic corks and rubber or silicone stoppers are used where biodegradability or chemical resistance is needed. Glass stoppers, often ground to achieve a tight fit, are common on laboratory flasks and burettes. In sealed vials, septa and crimp seals may be used, and sterile stoppers are chosen to maintain asepsis.

The stopping procedure depends on the context: in chemistry and biology, containers are filled, sometimes flushed with inert gas, and then stoppered with care to avoid introducing contaminants; in wine production, stoppers are inserted after fermentation to seal the bottle. Issues include improper fit leading to leaks, cork taint, or microbial ingress; closures are selected to balance seal strength, permeability, and compatibility with contents. Alternatives to stoppering include screw caps, twist-off caps, and crimp seals.