I'm intrigued to see that the curves for the lower ratios appear attractively S-shaped, while the highest dilution is ramrod straight. I'm pretty curious what they would look like if they were processed to the same zone VIII density.
I'm using your 40:1 ascorbic acid formula, but I could whip up a batch of 80:1 for this project, so I'll have the reserve capacity. (Although..., simply adding 5 or 10 ml of PC-TEA will keep the alkalinity up, which answers my first question. Hmmmm....)
Peter:
It looks like your first suggestion was right on target...
Incidentally, I use a variant proposed by Sandy King, in which I add 0.2 g of KBR to stop the streaking problem that used to plague me in the past.
Jay:
Now that I'm confident that my developer won't die after the first sheet, I'll probably make up a few pre-measured 5 or 10 ml batches of PC-TEA (diluted 2:1 or 3:1, so it'll blend in quickly), which I can toss into the tray after every other sheet, up to about 5 or 6 sheets maximum. My washer holds 10 sheets, so a 2-batch session before a beer break is about right.
As we both know, capacity and activity are not the same thing. The 3 liters may have capacity for 6 sheets, and if I could develop them all at once, the time would be a constant (say; 7 minutes). But if I develop them successively, the time must be increased successively to match the reduced activity (say, +10% for each succession). So the timing might be something like this: 7 min, - 7.7 min, - 8.5 min. - 9.3 min. - 10.2 min - 11.3 min., etc....
You're right, changing the developer every hour or so is not a big hassle. I make up a few 3 liter batches ahead of time (96 oz Chlorox bottles are perfect), and can make a dump/change in a few minutes.
If you ever come down Portland way, give me a call.. we could have fun making the neighbors suspicious with big tripods, and funny looking dark cloths....
I'm intrigued to see that the curves for the lower ratios appear attractively S-shaped, while the highest dilution is ramrod straight. I'm pretty curious what they would look like if they were processed to the same zone VIII density.
Don't be too enthralled. The step wedge was not calibrated. There are the usual sources of experimental error. If you look closely you will see that all the curves have some curvature. It is more apparent in the low contrast curves. The straight lines are those of best fit according to my spreadsheet program.
[QUOTE=Reinhold]Thanks, everyone for your suggestions...
Patrick:
I'm using your 40:1 ascorbic acid formula, but I could whip up a batch of 80:1 for this project, so I'll have the reserve capacity. (Although..., simply adding 5 or 10 ml of PC-TEA will keep the alkalinity up, which answers my first question. Hmmmm....)
Make up a batch of ascorbic acid in TEA without the phenidone to use for replenishment. The phenidone does not get used up, but ascorbate changes to dehydroascorbate which is not a developer and is somewhat more acidic than ascorbate. Along with the dehydroascorbate, HBr is formed in the development process, but only H2O by aerial oxidation. In a closed tank, there isn't much oxygen available, so one should be able to estimate pretty well how much ascorbate to add per unit area per unit density.
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Originally Posted by psvensson
