Does Rubbing TriChlor Puck on Stain Really Work?

I agree a vitamin C tablet (ascorbic acid) is the cheapest approach to stain id. If you are still confused by the stain, there is a product called Jack's Magic Stain ID kit that can help to identify a stain. They are a bit pricey so I would do the trichlor puck test (careful, trichlor is very acidic and you don't want to leave it on plaster for very long), then ascorbic acid tablet and then get the kit if the first two tests fail.
 
Thread Status
Hello , This thread has been inactive for over 60 days. New postings here are unlikely to be seen or responded to by other members. For better visibility, consider Starting A New Thread.