The wax was sterilized by boiling and kept in stoppered bottles. Manganese dioxide is then added and the flask stoppered. These reagents are added to a flask, mixed, and the flask is stoppered. Once full, the collecting flask can be stoppered. Wine bottle openers are required to open wine bottles that are stoppered with a cork. Early bottles were sealed with wax, and later stoppered with a cork. The tube is then stoppered and vigorously shaken. Both solutions A & B are prepared separately and stored in rubber stoppered bottles. They are often stoppered with proteinaceous "pit plugs". Typically, three identical transparent vessels are filled with sample water and stoppered. The collection vessel or still receiver can then be removed and stoppered.