Re: Paper negatives- Ink Selection
Using 2A:1B indeed gives a speed gain (w/o any significant quality loss). What does it to the characteristic curve of the process I can't say, since I never compared... Keith uses oiled negatives, whereas I don't. But still can get a good image and a nicely exposed gum layer (which develops in about 30 - 40 minutes, sometimes 60, which can withstand erasing another layer on top of it) with only 6:30 exposure. It looks out of the line compared to mine, and that's what makes me tend to think that it's something about DR and/or calibration. Full strenght AD would definitely increase speed considerably. But then (as a note) I personally don't like the characteristic curve (and results) I get with high dichromate. I was using 20% with plain paper negatives, then switched to 10% with translucent inkjet bond and the shadow separation seems to be better now. BTW, speaking about high dichromate concentration, comes to mind something interesting to mention about dichromate stain: I was getting dichromate stain (in darkest shadows) with plain paper negatives, exposed for 15 minutes, 20% AD. Then I switched to translucent inkjet bond, which - according to visible light measurement - is exactly 1.5 stop faster than plain paper. That makes 5:20 equivalent exposure time (with 20% AD) for the new negative media. I decided to halve the dichromate (to 10%) and increase exposure by 1/3 stop to offset the weaker concentration (not measured, just was testing if +1/3 stop will be enough). Therefore new exposure time became 5:20 + 1/3 stop = 6:40 (which was cut to 6:30 later), for translucent inkjet bond, 10% AD. I don't get dichromate stain anymore. That can be attributed to the fact that I'm giving less exposure to the emulsion, but then I can't explain why I don't loose even a little bit of highlight detail using the same negative and same development time!? If I was giving less exposure (absolute) to the emulsion, then I should have loose highlight detail, don't you think? But I don't!? Could it be not only absolute exposure (the total energy the emulsion gets) but also the exposure time does have an effect on dichromate stain? (Or what else?) I'm not claiming anything, just sharing something that confuses me (a lot)... Any thoughts? Regards, Loris. 15 Ekim 2008, Çarşamba, 7:13 pm tarihinde, Christina Z. Anderson yazmış: > Keith, > Have you tried mixing your cyano 2A:1B to cut down one stop? > > I don't think the 15 min is out of line since I use Pictorico with gum and > a > 6 minute exposure. > > Why aren't you using full strength am di? Or 15% perhaps, instead of pot > di > to decrease your times, too? > Chris > > > Chris > >> Hi Loris, >> >> My gums require 15 minutes with oiled negatives. I would really like >> to reduce this. Also, cyanotypes made with the same oiled negatives >> require exposure times of 30-45 minutes. How does this compare with >> others? It seems pretty long. >> >> Keith > > >
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