you're exposing the film just as you would a 4x5 film holder w/o a darkslide. it'll cost you about $1 or you could just do it in the dark. Alex, I think or Dap. there's not that many options for black but maybe someone else will chime in or tell me I'm wrong. wear nitrile or latex gloves, don't get that shit on your hands if you don't have to.