2- batch RA-4 processinggreenspun.com : LUSENET : Large format photography : One Thread
There is a basic model of color paper processor from Durst with 2 tanks which I assume does not use stop chemical for RA-4 processing. Fujimoto, however, makes one model with 3 tanks and I think stop chemical can be used in the second tank. My questions : 1)Is it OK not to use stop in RA-4 processing without comprising in quality? 2) Does any one has actual experience to share with in using these two models? I appreciate your advice in advance. Chen-Wah Lee
-- Chen-Wah Lee (email@example.com), August 04, 2001
typically a roller transport machine does not use any stop between the ra-4 dev and the blix. rather there is usually a water crossover that is fine. i suspect the differences between the machines is the fujimoto has an extra tank that is a wash tank after the blix,i believe this was an additional module with the durst machines. hope this is helpful. robert
-- robert (firstname.lastname@example.org), August 13, 2001.
Chen-Wah, most larger processing machines do NOT use anything between developer and bleach-fix (blix). They normally run automatic replenishment, where the blix replen is extra-concentrated and has an extra-low pH to counteract the effects of developer being carried over (ie, dilution and raising the pH of the blix). Normally squeegees are recommended as the paper exits the developer tank to minimize the solution carryover into the blix tank; in a roller transport machine, two rollers together have the same effect as a squeegee. In a pro lab, the blix pH would be checked with a meter and replenishment rates (for blix) would be accordingly adjusted.
As long as the paper is quickly immersed into the blix with agitation, AND no blix splashing back towards the developer, this type of processing system is fine. If you were to splash blix onto paper before it submerges (into blix), it will probably make dark (cyan?) spots where the droplets hit. I would not expect any processor to splash like this, but do not have experience with those you named.
There is a very good book "Post Exposure" by Ctein; he says, "I use a Durst/Nutek RCP 20 modified to run at RA-4 speed.". Hope this helps.
-- Bill C (email@example.com), August 13, 2001.