There are two main types of soft solder; lead solder and lead-free solder. Lead solders have about 60% (or 63%) tin and 40% (or 37%) lead in them. They are toxic because they have lead in them. They melt at around 185°C. Lead solder is cheap, so it used to be popular. In plumbing, a 50% tin and 50% lead mixture was used. People thought this was safe, but then they saw that the lead was coming into the water. Now lead solder is illegal for water. Lead solder was once used for food cans. After many years, the lead could come into the food. The cans poisoned people who ate the food. Lead solder is still used in electronics.