Invented in the early 1900s by Eugene Charmat, this procedure was implemented as a faster and less expensive way to mass-produce sparkling wines. Also known as the "closed tank method" this process uses a large, pressurized stainless steel tank (autoclave) to create the bubbles which are so important to the characteristics of the sparkling wine. If needed, sugar is added with the yeast, allowing a second fermentation to take place quickly in the sealed tank as the yeast begins to develop the bubbles. With the use of refrigeration, temperatures are controlled to improve and maintain the quality of the product. Following the fermentation, the wine is kept pressurized while bottled, to keep the carbonated bubbles fresh and plentiful.