I have been using Shandon Sequenza for the last two years with no problems. Lately i have noticed small spots under a microscope that have not been stained by DAB (only hematoxylin as a contrast color is there). I am pretty sure that my technique of putting a cover plate and a slide together is fine, and i use a new cover plate each time. If anyone who uses SS in their Immunohistochemistry staining has any advice on what this could be and how to solve it, please let me know. Thank you!