Self-Fluxing Solder with Flux Cells: Kester, 1899

Jesse F. Kester of Buffalo, New York, patented this solder in 1899, US 628,541. Solder wire with one continuous core of flux already existed, but the flux melts at a lower heat than the solder, so it melted some distance back from the end, too much ran out at each joint, and little was left near the end for the next. Kester divided the flux into a row of separate closed cells: each melt opens one cell and supplies a uniform charge of flux.