Has anyone experimented with using pyro developers for making wet plate negatives? I have only used the standard ferrous developers with which we are all familiar. I am curious what the difference is in using pyro. John Coffer's manual seems to promote the iron developers over pyro (note: I don't have the manual at arm's length, so I am writing from memory) yet I've enjoyed using pyro with film in the past. Does the pyro stain the emulsion as it does with film? It seems as if it was quite popular in the 19th century so here must have been a reason and I am curious what those advantages might be.

Anyway, just wanted to hear what zany users' experiences have been. Thanks!

I've used pyro in the past (I actually was just "conversing" with Mark Osterman over the internet regarding pyro) and they produce beautiful negatives. The "drawbacks" are longer exposures (as opposed to iron developed negatives) and unless the plate is subbed with albumen the collodion tends to peel easily (the pyro shrinks the collodion). Just this week I was looking at negatives I had made over 10 years ago with pyro, comparing them to my more recently made iron-developed negatives. There is a noticeable difference. However, as Mark noted, one doesn't really need pyro for a properly exposed and developed (in iron) negative in good light. For me, strong light seems to be a prerequisite.

Dave

Is there much of difference I the 'speed' of the emulsion between the two developers? Thanks a lot for the info!

pyro takes some getting used to. it works slower than ferrous sulfate develop, since the chemical action is different. not good at all for positive images, since the image has no whiteness to it. all your stuff turns black when you use pyro. the actual grain, if you can call it that, of a negative is much smaller when pyro is used, so for superenlarged images it can be a help.. otherwise, just a pita to use.