More Caffenol

There’s been quite a bit of experimenting going on since my last blog entry. I have had some success with my coffee developing, but I was not getting the results I hoped for. I developed quite a few rolls of film that finished with a very faint image in the negative. This would result in a very dark image when you make it “positive”, which would mean I either underexposed the film (I’m pretty sure I did not), or I under-processed the film (most likely the case.)

I decided to get to the bottom of the problem, rather than fulfill the definition of insanity (“Do the same thing over and over, expecting a different result”).

My first concern was that I was not making the buffer properly. I found some pure Vitamin C powder online (through Walmart!), and bought some pH test strips. I know that for the silver to properly develop the coffee solution has to be alkaline (pH higher than 7), so maybe i was adding too much Vitamin C and not enough washing soda. This would leave the coffee solution with a pH too low for proper silver development.

I measured out the washing soda and Vit C, dissolved them separately (no more messing around with those messy Vit C tablets with all the gummy additives), and tested the pH before mixing. The pH of the soda alone was nice and high, around pH=12, and the pH of the Vit C was low, around pH=2. That was to be expected. Now, what pH did they settle in at once mixed? To my relief, the final pH was around 10, well in the alkaline range.

The last thing to confirm that the buffer was capable of raising the pH of the coffee, from about pH 4 to above pH 8. Happily, that’s precisely what happened. The test strip on the left shows the pH of plain coffee (acidic), and the test strip on the right shows the pH with the buffer added (basic, or alkaline).

pH of coffee before and after buffering
pH of coffee before and after buffering

With the pH question settled, it was now a question of developing time. I had been using a standard developing time of 14 minutes. According to reports on the caffenol information website, this should be enough time. Now, it is possible I was not making my coffee strong enough, and that could be part of the reason for under-developed film, but I decided not to change that part of the recipe just yet. Instead, I ran a test to see the effects of adding more developing time.

To do this, I shot a couple of rolls of film (fresh Kodak 100TX), where I took the same two images over and over. I walked down to the plaza in front of the Civic Center and Rochester Art Center, where the Po Shu Wang public sculpture sits. A digital image of the Po sculpture with the Plummer building in the background is below.

Henry and Po
Henry and Po

When it was time to do my test, I opened up the film canister in the dark bag, and then cut the film into lengths that I estimated were about six inches long, and therefore would have about four frames in them. Of course, I had no idea where the frames began and ended, but no matter, I just needed two intact images in the middle of the length. I loaded each length onto its own spool, and put each spool into its own tank (I have five tanks). Now I could run a control (using the same technique as previously used), and four experimental techniques.

I had seen from other photographers on the caffenol Facebook page that they had success with a technique known as “stand” developing. In this technique, you pour in the developer, give a quick agitation to get any bubbles off the film surface, then simply let it stand with out agitation. Stand times can range from 30-70 minutes, or anything you want. I chose three stand times: 35 minutes, 45 minutes, and 60 minutes.

I did the control first (14 minutes with agitation each minute), and got the same “thin” image development as before. Now, you can “rescue” these underdeveloped images digitally with scanning and manipulation in Photoshop, but I wanted to see some real silver!

Off to the first experiment. I poured fresh caffenol into the tank I had labeled for 35 minutes, and let it stand. Since it was just going to sit for a while, I used the time to set up the 60 minute tank. I could follow the steps for the stop bath and fix bath for the 35 minute tank and be done in time to do the same for the 60 minute tank. I poured the caffenol into the 45 minute tank just before doing the stop bath on the 60 minute tank. Are you following this?

I was delighted when the 35-minute experimental strip came out of the tank to see that there were clear and discernible images. I let that strip dry, and moved on to the 60-minute tank. It, too, had distinct images, and at first glance maybe looked a little too developed. The negative was pretty dark, but not so much so that the images were obliterated. Last to come out of its tank was the 45-minute strip. It has nice rich negative images on it, with plenty of silver. Here’s a view of what the strips look like held up against a white light source (my computer monitor.)

Film Negative Comparison
Film Negative Comparison

And here are some comparisons of the images generated after scanning each negative. Some of the differences are compensated for by the scanning software, so the exposures appear more equalized than they really are.

Image 1 comparison
Image 1 comparison
Image 2 comparison
Image 2 comparison

At this point the clever observer may have noticed two things: 1) there was a fifth negative with no apparent images on it at all; 2) the upper left image in the comparisons shows an odd pattern at the top of the frame. What was experiment #5 all about, and what is going on with that funky pattern? That, my friends, is a story you will have to wait for in my next blog. After all, every good experiment should leave a few questions unanswered, or inspire new questions.


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