The wet collodion process, when used to make ambrotypes (on glass) or Tintypes (on black japanned metal). I know it is actually developed as a negative, and then appears as a positive against a dark background. My question is this....what is it about the process that allows the developed silver compounds to appear lighter than they do on modern negative materials? Is it the developer, the actual silver compounds or the "cyanide" type fixer? (or a combination?) In general, what contributes to allow the developed/fixed image to appear light enough to "read" against the dark background?