This blog entry is going to be short and sweet -- As it turns out, I was very close to full success with reversal processing. After substituting in the new Dufaycolor first developer, the plates immediately looked great!
Current thoughts on coating:
Right now I'm sticking with the 'pour off' method I described earlier, as it seems to provide fairly consistently good results. Before coating, I prepare a carpentry square, carefully balanced to be PERFECTLY level. I allow the screens to rest on the square while I am preparing the emulsion.
1. Heat the emulsion to 45 - 50C
2. Apply 20mL of emulsion to a 4x5 screen. If it has not spread across evenly, gently use your finger to aid the emulsion across the plate. The emulsion should be very thin and runny.
3. Tip the corner of the plate and pour the emulsion back into the beaker containing the emulsion. Drain until the corner is only slowly dripping.
4. Set the plate back on the square and allow it to dry.
What we are hoping to do here with this technique is to get a nice, complete coating across the plate, not so thick as to hinder the reversal processing, but also not too thin so as to lose density. Ideally, when you are setting back the plate in step 4, the emulsion is still runny and will coat the plate with a consistent thickness before it begins to gel up.
Currently my emulsion is very slow, ~ISO 1, so I'm able to coat these plates under a red safelight. The plates are not directly under the light, but rather a few feet away, and I coat them using the glare of the light off the surface of the plate. Subsequent handling of the plate (including development) is also performed under the safelight. I have yet to see any evidence of significant amounts of fog.
My problems with development have all vanished since switching to the Dufaycolor first developer recipe taken from here, which is as follows:
The plate was developed in this solution for 5 minutes at 15C.
After washing thoroughly with tap water, the lights should come back on. The plates are bleached with sulfuric acid / potassium dichromate as outlined in my previous post. The bleach time can vary -- sometimes the coating is a bit thicker in a corner and will require more time. Usually this takes about 3 minutes with agitation. The plate negative will gain contrast as the tan silver dissolves away, leaving visible the dark screen behind it. After bleaching is complete, wash thoroughly and clear the plate in sodium sulfite for a few minutes.
Second development is simple. I am just using stock Dektol. The goal in this step is to convert all the remaining silver halides that have been exposed to light to silver. After second dev, wash the plate thoroughly.
You're done! There should be no remaining silver halides, and thus no need for fixing. Admire your work -- hopefully something came out!
Thoughts on reusing the screens:
Anyone playing around with this process will quickly realize that the screens are the most painful part of the process. So far, I have found that they can be reused several times. The gelatin can be gently 'massaged' off while running under hot water -- this seems to be most effective, with the exception of some stubborn spots. The emulsion can also be scratched off with a finger nail, though I recommend doing this under cold water, as the second varnish becomes tacky when it is heated. Both methods seem to damage the screen slightly, creating small scratches or other defects. So far I have yet to have one fail -- I think the most uses I was able to get out of a screen is 5. If one is gentle, hopefully it can make it through several more.
I'm very excited to have such good results so suddenly. Over the next few weeks, I am going to try and compile my findings into a guide, like my Lippmann Guide or Daguerreotype Guide. There is still so much to improve and discover about this process, and I hope other excited photographers will be able to get their hands dirty with it too. Until next time.