I am now doing trap staining with my paraffin-embedding slides. The kit I bought is from Sigma Aldrich. According to the protocol they provided, I made 2 groups. One with tartrate solution, one without, then I incubated the slides in the mixed solution. But the problem is in both groups, I can see dark purple staining cells around the bone, which I guess should be the osteoclasts. does anyone know how it happened? And I checked some literature, what they stained positive is always red...I really don't know where goes wrong.. Can anyone provide me the protocol if you can make positive staining with this trap kit? Thanks a lot in advance!