3.5
Atmospheres of pressure in most Proseccos, equal to 51 pounds per square inch (PSI). By contrast, Champagne and California sparkling wines both have about 6 atmospheres of pressure, or 90 PSI, which is three times the pressure in a car tire. The increased pressure explains why Champagne and California sparklers are sold in bottles that are heavier and thicker than Prosecco bottles.