I was experiencing a now nearly extinct phenomenon known as ice bridging. Ice bridging is when the boots push the ice out, but the ice doesn’t break off, creating a layer of ice that is separated from the boot by an air gap. Most modern boot systems have more advanced technology to prevent this, but for early boot-equipped aircraft, it was a problem. The wing continued to get heavier, and the performance continued to decline, so I immediately executed Plan B by descending to 5,000 feet where the temperature was above freezing. As the ice melted off the wings, my immediate crisis was averted, but I now had an additional problem: The freezing level across the remainder of my route was at the surface, and I had to avoid icing at all costs.