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Pre-rinse with Ra-4



 
 
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  #1  
Old March 28th 04, 06:23 PM
Nick Zentena
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Default Pre-rinse with Ra-4

A while ago some discussion happened on using a pre-rinse to over
come green tint on the paper. I did some not very carefull testing. With the
paper I cut from a roll of Supra III a rinse really is needed. Not doing it
seems to really cause green meanies. OTOH using Supra Endura pre cut from
Kodak it doesn't seem needed. An obvious difference is the colour of the
rinse water post rinse. With the Supra III it's very blue. With the current
Supra Endura the blue is just noticable. OTOH it seems the rinse does other
good things. It pre-heats my drum. The paper seems to soak up some water so
it's not soaking up developer. I think that'll lead to longer keeping times
for the developer. I used to lose a little developer with each sheet leading
to an ever growing head space in the bottle. The only potential problem I
can see is increased dilution of the developer from the rinse water.

Something I don't understand is why I need to dry the drum so well to
avoid spots but I can do a pre-rinse and no spots.

I guess my point is a pre-rinse doesn't seem to do any damage and it
does seem to help so I'm going to keep doing one.

Nick
  #2  
Old March 29th 04, 12:25 AM
Jazztptman
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Default Pre-rinse with Ra-4

Nick asked Something I don't understand is why I need to dry the drum so well
to avoid spots but I can do a pre-rinse and no spots.

Nick, probably because the paper is so very sensitive to water spots swelling
the emulsion and not giving you even development. when you prewet and soak the
entore emulsiion at the same time, nothing stands out. But when you get a few
water spots or runs from excesse water in the drum and the developer hits the
paper, you get a different pattern of development where the paper was already
wet.

As far as the difference between the raw stock color, there is a large change
in color from Supra III to Supra Endura. it has nothing to do with roll verus
precut sheets. The color you see and that comes out in the developer or
pre-rinse water is just sensitizing and other dyes used to make the paper.
These control the speed of the emulsions for batch to batch consistency, and
make each emulsion layers silver halide sensitive to the proper color of light
when it is exposed.

This dye does wash out during the process, and it should not make any
diffrerence whether you pre-rinse or not.


Bernie
 




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