1) Casto-Tin #1 is a soldering alloy paste containing 30-60% tin, 30-60% lead, and 10-30% zinc chloride. 2) It is a dark grey paste with a heavy odor, moderate solubility in water, and stable at room temperature. 3) Exposure can irritate eyes, skin, and respiratory system, and ingestion of fume residues can be poisonous due to lead content.