Blocking is performed after the slides are printed and before they are hybridized. The Bauer Core’s blocking protocol for poly-lysine slides includes several steps: rehydration and snap drying to improve spot morphology, UV crosslinking to permanently attach the nucleic acid to the slide, and chemical blocking to inactivate the slide and prevent further DNA from binding. When double stranded DNA is printed (as in PCR products), a denaturation step is included at the end of the protocol. The protocol for blocking 15 slides takes about an hour. Please direct questions about blocking arrays to Christian Daly (email@example.com).