I have soaked needle work blocks in OxiClean max and stains have come out. The blocks that I did this with were 40 years old and thread that was used in these blocks is the same that would be used in her blocks. Just mixed a little in water, put blocks in and walked away for a few hours. One of my blocks was really badly stained so it just soaked longer than the other. Never would have known that there were stains now
