Solder-It Plumbers Solder CSP-41 Copper Bearing Solder Paste . Our Plumbers Solder Paste is lead free and also contains NO cadmium or antimony. As with all of our pastes, no flux is required. The low melting temperature enables repair to existing joints without disassembly and makes professional pipe joints with ease. Solder-It Plumbers Solder works on all of the same metals as our Silver Bearing Paste but is formulated for use when joining heavier gauges of those metals.