I have been using the DAB Substrate Kit from Vector Laboratories. The Kit
comes with an Optional Nickel Solution to give the metallic gray staining.
I have not encountered any background problems using this kit. Alos I
counterstain with Vector's Haematoxilin which gives me really good
contrast.

Nima Farsinejad
Research Specialist
Digestive Diseases
Emory University
Atlanta, Georgia