When a glass of champagne is poured, the bubbles are beautiful to watch. Champagne contains carbon dioxide, as well as tiny dust particles in the glass. Why does the champagne lose its sparkle? Is the juice stale? Did it go bad?

Someone cleaned a container too well.

Champagne, as the name suggests, is an effervescent wine. The sparkle in most soft drinks is produced by carbon dioxide (CO2) and champagne uses the CO2 naturally formed during the alcoholic fermentation of sugar in the grape juice, which has been fermented by yeast. The bottles are then sealed so that the CO2 generated does not escape, increasing the CO2 concentration in the champagne.

If your champagne does not sparkle as much as you think it should, it is because the glass is too clean. The bottle contains impurities that help the CO2 bubbles stay longer, resulting in a more consistent fizz. CO2 is released when it comes in contact with the micro-limescale contained in the dirt inside a glass. The fizz increases in champagne, so if you don't want to waste your champagne, use another glass, without cleaning it.
If your champagne is older than its shelf life, it may not be safe to drink.

Loss of fizz in champagne can be due to the drink expiring or to poor storage. How to detect it?

If the champagne is not stored properly, the CO2 will dissolve in the liquid and the champagne will not have enough effervescence. If the champagne is not sparkling, here is another reason.
The darker the color, the more oxidation has occurred and the golden color becomes more yellow.
If you let the champagne sit too long, not only does the carbonation disappear, but the fresh smell also disappears. All that remains is the aroma that the champagne has acquired through aging. You've waited too long to drink it, and now it has gone bad.
A champagne that has lost its carbon dioxide is less acidic in the mouth. You would feel like you are drinking flat juice without any sparkle.

Keep your champagne sparkling by preserving the bubbles.

To keep the champagne bubbles strong, put the champagne in a thin glass that is slightly wider at the top.

The glass should not be rinsed before serving, as rinsing will remove tiny impurities from the glass. These impurities are not healthy to have in your glass and cause the gas to get stuck inside the glass, creating bubbles.

The cooler the champagne is when served, the higher the fizz.

Keep your champagne cool by using a cork.

Professionals use champagne towers to keep the champagne bubbles for a long time. This method is used along with other preservation methods to maintain the quality of the champagne.

If your champagne has lost its bubbles and you want to reuse it, you can make vinegar out of it. You can also use the champagne that has lost its bubbles in other recipes.