Film: Fortepan 200
Time: 54 min
Agitation: Continuous inversions for the first 30 seconds and then 10 seconds agitation every 9
minutes rotating the tank 1/4 turn every agitation
Presoak: 3 minute water presoak
Camera/Lens vintage: 1952
I recently began experimenting with GSD-10 and a particular "old school" emulsion, Fortepan 200. Along the way I encountered some problems and found some solutions I would like to share.
When experimenting with a new developer/film combination there is often not a lot to go on, but there is usually information you can start with. While there is no information out there on the GSD-10/ Fortepan 200 combination there is information to leverage. Luckily there are development times and dilutions for several films on this GSD-10 blog. On the Massive Development Chart there are development times for those same films but with developers like D-76. Jay has a PF+ full stand development time for 1:10 dilution and a certain EI in one of the early blog entries. I looked and compared the D-76 time ratios of Fortepan 200 to PF+ and took into account that I wanted to shoot at box speed. I used that information to determine a good starting point for stand development with GSD-10 1:10 and Fortepan 200.
A good thing to do is try that starting point out with a negative shot in a controlled lighting situation. Since I don't have a densitometer, I metered a simple still life that included a print gradient, a grey card, and some real world objects that provide a good test of the shadow detail and highlights. The next task is to take those negatives and find the development time that best reproduces the still life and provides both the right shadow and highlight detail. I found that 32 minutes gave me the right image at 70F (21C). So I had found correct full stand development time and temperature for 1:10. But alas, I noticed that the negatives processed this way had streaks where there was a long black object in the photo. You can see this in the example below. In the image there are white streaks below the black mirror frame. So it became clear that full stand development would not work with this developer and film combination at least at this dilution. However, i was able to eliminate the streaking by going to Low Frequency Agitation development and finding the minimum agitation that gets rid of the streaking.
To eliminate the streaking I first tried an agitation half way through developmnent. I dropped the development time to 30 minutes since there was increased agitation. But there was still some streaking. The next thing to try was agitation at 1/3 and 2/3rds of the way through development. That worked. I was able to eliminate the streaking when I agitated at 9 minute intervals with a total development time of 27 minutes. The resulting negatives have nearly identical grain size, acutance, and tonality as the full stand developed negatives. I had arrived at a successful Fortepan 200/ GSD-10 combination of 1:10 dilution, 70F (21C), 10 sec agitation at 9 minute intervals, and semi-stand development. With that working well I set about seeing how things would work with a much more dilute Working solution of GSD-10. Since the Fortepan 200 I'm using is 4x5 format, the development tank needs 1300ml. So using a more dilute solution is appealing as that reduces the cost per negative noticeably. The danger of overly dilute developers is that the chemicals will exhaust before development is complete. This happens when there is not enough of the actual development chemical in the tank to complete development. I knew that Jay has examples of successful 1:10 development of 35mm on this blog. Most 35mm tanks hold about 300ml. The 1300ml 4x5 tank holds over 4X the volume of chemical. So 1:40 dilution or higher appeared possible with this tanks size and 4 4x5 sheets without exhaustion. In terms of surface area to be developed, (4) 4x5 sheets = (1) 35mm 36 exposure roll = (1) 120 roll.
Because I wanted to keep the development time under an hour, I focused on a 1:30 dilution. I tried various development times using the same 9 minute agitation intervals but found the negatives to be thinner than the 1:10 negatives unless I was willing to go significantly longer than 1 hour. Instead I raised the temperature. I found that by raising the temperature to 77F (25C) I got a great 1:30 result at 54 minutes. My Low Frequency Agitation, 1:30/ 77F/ 54 minutes produced a similar negative density to 1:10/ 70F/ 27 minutes. Temperature is definitely something you can utilize to find development times you like. Note that 54 minutes is exactly twice 27 minutes which will be a very interesting ratio to try out on other films and dilutions.
One advantage of the 1:30 dilution and perhaps the temperature increase is that the grain appears to be finer than with the 1:10 dilution. Below is a crop of a portion of the "porch picture that shows off the fine grain. Click on the photo to see it 1:1. You will see he small grain size in the 2400 dpi scan of the negative.
I am very happy with the 1:30 GSD-10 results and this is my new favorite developer for this film.