Simplify the following text for a Grade 6 native English-speaking person.
Original: Since even small amounts of lead have been found detrimental to health , lead in plumbing solder was replaced by silver ( food grade applications ) or antimony , with copper often added , and the proportion of tin was increased ( see Lead-free solder . )
Simplified: There are two main types of soft solder ; lead solder and lead-free solder .