Pressure Cooking Vegetables "In pressure cooking vegetables, follow the directions that came with your cooker, but learn to adjust cooking time to suit the quality of vegetable being cooked." A pressure cooker uses steam from water or broth to increase pressure inside the sealed cooker. The trapped steam increases the temperature. Once the pressured steam is released from the cooker you can safely remove the lid and finish prepping your meal. The first known pressure cooker was invented in 1679 by a French Physicist. In 1938, Presto released their pressure cooker with immediate success. Unfortunately, the first World War brought the need for aluminum to the war effort. A lot of companies couldn't get the aluminum they needed to produce products. After the war, pressure cookers would make an explosive comeback. Many manufactures were not making the cookers with consumer safety in mind. The pressure release valves would get clogged and BOOM! ...