The 17th and 18th centuries brought two major innovations that once again made it possible to age wines for many years, a possibility that had disappeared when the impermeable amphora was replaced by wood barrels. These momentous developments were slim bottles and cork stoppers! The English discovery of sparkling Champagne depended on the fact that they had begun plugging bottle necks with compressible gas-tight cork instead of cloth, and that they had especially strong bottles that could withstand the inner pressure (the glass strength came from manufacturing with hot coal fires rather than wood fires). And during the 18th century, the wine bottle gradually evolved from a short, stout flask to the familiar elongated bottle. The bulky bottles were only used to convey the wine from barrel to table or to hold it for a day or two. When bottles had slimmed down enough that they could lie on their sides, their contents wetting the cork and preventing it from shrinking and admitting air, then wine could be stored in them for many years without spoiling, and sometimes with great improvements in flavor.