Development times for dilute concentrations of developer

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I'm wanting to experiment with dilute concentrations of developers (specifically HC-110) and was wondering what the relationship between deveopment time and concentration should be. For example, if I halve the concentration of developer, should I (roughly) double the development time? Or is there some logarithmic or other function I should be following?

-- Scott Flathouse (scott@pan-tex.net), June 07, 2000

Answers

Not knowing the chemical kinetics of the reaction, this is hard to answer. What I would do is this:

Collect all the data you can get (from the forum members, from data sheets, etc.). If you have one, use a spreadsheet program to evaluate them as described below.

Assume you got 6 mins at 1+4, 9 at 1+7, and 12 at 1+12, all of them at 200C, one-minute agitation, and for the same film to keep things simple. Now select a reference dilution, such as 1+7. Express all of the values as multiples of the time at reference dilution, i.e. 0,67 @ 1+4, 1 at 1+7, 1,33 at 1+12.

Draw a plot of these normalised times over dilution, and see if there is a correlation. If it is poor, this may be because the data you have were not all for the same values of the other parameters (film, agiation, temp). Then apply the procedure to a limited pool of data, such as "only those for film XYZ" or "only those for one-minute agiation", or, if nothing else helps, and if there are enough data, only to "those for film XYZ, at 200C, with one-minute agiation". Provided there is a correlation, try to extrapolate it to the dilution you are interested in.

-- Thomas Wollstein (thomas_wollstein@web.de), June 08, 2000.


Thanks, Thomas, for the help. I may have answered my own question, though. I briefly perused Kodak's data sheet for HC-110 (which I should have done in the first place) and they list a development time for solution A (1:15 dilution) for Tri-X at 4:15/68 deg. F and a development time for solution B (1:31 dilution) for Tri-X at 8:30/68 deg. F. Essentially double the time for half the concentration, it appears. Unfortunately they don't list development times for the more dilute solutions. However, I believe I have a good starting point now.

-- Scott Flathouse (scott@pan-tex.net), June 08, 2000.

They are not a linear link. The time changes more with just a slight change in the developer. I found a couple minute change just changing HC-110 from 1:8 to 1:10. Maybe it works out, but you can't bank on it. I find HC-110 at 1:15 for about twelve minutes good for soft T- Max 100's. I begin the agitation normally, but spread it out longer toward the end. By five or six minutes, I start to add time between agitations, until the last one sits for about two minutes. That helps soften contrast too. You can't do that the entire time without risking uneven film. I think I have played with it at around 1:30 as well.

-- E.L. (elperdido65@hotmail.com), June 09, 2000.

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