Upslope refers to the gradual ramping of weld energy. Closed-loop resistance spot welding power supplies allow a very precise upslope to be programmed at the beginning of the weld pulse. This upslope of current, voltage, or power helps to reduce the initial contact resistance, focusing weld heat into the parts and reducing weld splash. The length of the upslope period can be programmed to suit the application. A long upslope is recommended for very hard or resistive parts.