Large Format Photomicrography part: VII

In the previous post I wrote a little about the options for processing chambers and in the post before that a little about the chemistry that does the work. Now to put that to use!

The Plan

Out of something like home team spirit I’ve decided to go with chemistry from Eastman Kodak. Nothing exotic or home-made; all these chemicals are exceedingly well understood, readily available, economical and are rather more forgiving than some of the film processing guides out there represent. In fact, most photographic chemistry is surprisingly forgiving-there’s just a drive for consistent results that pushes folks into a corner and makes many too afraid to try or to color outside the lines. Everything will be happening in a daylight color print drum.


Everything needed to process


The film I exposed earlier is Arista EDU Ultra 100 ISO 4×5 black and white. In photomicrographic use lower ISO speed is generally a better bet than higher because it will exhibit a smaller grain size and permit the use of the longer exposures that provide good contrast in this the world of photomicrography. As a rule it’s also far less expensive than ISO 20 film. Many of the older texts on photomicrographic process recommend speeds as low as ISO 7, or even 4!


I’ll use Kodak D76 as my developer and dilute the working solution 1:1 with tap water for a 10 minute processing time. Kodak D76 is a classic and versatile black and white developer that does just fine in a tray, drum, or tank. What’s more, it’s so widely available that a quick search can usually turn up an account from someone using it in exactly the way a novice is considering. There’s data and recommended processing times for just about every film out there. Guides on stand developing (where there’s no agitation during development), continuous agitation, and drum processing abound. There are dilution possibilities for almost every need and temperature recommendations for nearly any conditions.

First about dilution. One can use D76 straight and undiluted or water it down to varying degrees. As a general rule the less diluted the working solution the faster it acts on the films emulsion. However, It would graph as an asymptote and concentrating the solution beyond a certain point will not decrease the developing time simply because the developer won’t have sufficient time to act upon the films emulsion. Conversely, diluting the solution too much will not extend the processing time beyond a certain point. Put another way, if making an acetic acid and sodium bicarbonate (vinegar & baking soda) volcano one will reach a point where using less acid will not make an eruption just as one will reach a point where using more will not make the reaction continue. For the most part one will not notice a difference in film processed in straight D76 for 6 minutes or D76 1:3 for 12 minutes (some people will claim to see a huge difference but will then proceed to upload zero examples or show anyone their proof). Is there a difference? Yes, one of those is going to look slightly different but unless your pushing the limits making a poster sized enlargement from a 35mm negative and using a hand lens to examine it, you won’t notice it and there are other things that will have a much bigger impact than dilution. Pick a dilution that sounds good and go with it, this is about just seeing if I can do this not if I can make a negative without grain detectible under a hand lens!

As for temperature there is an insane amount of importance placed on it, why? Well anyone who took a chemistry class knows that temperature has a big impact on reaction time, and film processing is all about chemical reactions. The rule of thumb is hotter temperatures cause faster more complete reactions than colder temperatures which still happen but happen slower and are less complete. Some folks read that the packet of developer says processing takes 9.5 minutes at 20˚ C when diluted 1:1 and think that’s a rule. It’s not, that’s just a starting point. That’s just saying that if you always develop under those conditions you’ll always get the same results from an identical negative.

There’s all manner of water baths and water bath heaters that keep ones chemicals at just the perfect temperature for processing. Those would be handy if they were portable but for the most part modern room temperatures are depressingly stable. 20˚ C just happens to be magic, it’s the so called “room temperature” of science. So what temperature should one strive to process at? Why your own personal room temperature of course! Don’t bother with folks who put extreme emphasis on temperature, and don’t bother pointing out the fact that a thermometer that isn’t regularly calibrated can be off by as much as 5˚ C. Is getting a consistent temperature ideal? Yes. Is consistency important? Sure. Is it super-ultra-stress-about-it-so-much-you-don’t-even-try important? Hell no! There’s no need to needlessly complicate this, look up the time recommendation for D76 for whatever room temperature happens to be on site and use that.


Water water water! Distilled? No! You’re not pumping your drinking water out of a limestone cave, it’s not going to leave hard water concretions all over the place after a minute long bath! Set aside a jug or two of water and let it come to room temperature or just get good at adjusting the taps on the sink. A minute of processing in a plain water stop bath is perfect.


Kodak Fixer (Kodafix, a.k.a. Kodak Professional Fixer). Purchased as a condensed liquid it’s diluted 1:3 for the working film solution and takes from 5-10 minutes according to the bottle. I’ll go with 5 minutes. Mixed from powder it’s used 1:1 as it mixes to make the working solution rather than the condensed stock. Unlike the developer which I’ll discard after a single use (it can be saved and one can add a bit of D76R-the R is for replenisher to get it back to working strength) the fixer will be saved. A given volume of fixer has a given capacity of material that it can fix. This capacity is generally rated in some specific quantity that one will have to use to calculate for their own needs.

A volume of 3.8L of 1:3 dilution of Kodafix has a film fixing capacity of 120 rolls of 36 exposure 35mm film. A single roll of 36 exposure 35mm film has a surface area of 0.0465 m² so 120 rolls would have a surface area of 5.58m² which works out to 8649.017 in² or 432 sheets of 4×5 film, if I mix up the whole bottle. My little 4×5 print drum takes not quite 50ml of solution. So 432/3800=x/50 meaning I can mix up 50ml and use it for 5 and a half sheets (5.68 sheets of 4×5 film for every 16.7ml of condensed stock solution).

Fixer should be replaced when it takes twice the time to clear undeveloped film that it took when it was fresh. What does that mean exactly? Take a strip of film cut from a fully exposed but undeveloped sheet (or the leader cut from a shot but unprocessed roll of 35mm) and drop it into your fresh working solution of fixer. Time how long that piece of film takes to turn clear, and that’s the clearing time. The fixing time is double the clearing time. After you’ve processed a whole bunch of film test it again for the clearing time. It’ll be longer than it was when you started but probably not double the original clearing time. Double the new clearing time to get your new (slightly longer) fixing time and keep right on going.


After fixing it’s time to wash it five minutes or so in a plain water rinse is all that’s needed for that. If someone does happen to have particularly hard water, or a very humid environment it can be a good idea to spend $20.00 on a bottle of something like Kodak Photo Flo. A couple of drops in the final water wash will help dry the film without streaks or water-spots. It handle necessary though and is really just a way to sell photography people a surfactant, Worth it though, if your having troubles on that end of things.


  1. Load a sheet of exposed 4×5 into print drum inside changing bag
  2. From stock solution of D76 make 50ml of working 1:1 dilution in a beaker (25ml D76 & 25ml tap water)
  3. From concentrated Kodafix make 50ml of working 1:3 dilution in a second beaker (17ml Kodafix & 33ml tap water)
  4. Pour working solution of D76 into drum
  5. Turn drum on it’s side to release developer and roll drum back and forth on table for 9.5 minutes
  6. Hold drum upright over sink to drain
  7. Turn on the sink taps and let the drums internal cup fill with water, release the water roll it around briefly before allowing the water to drain, repeat as many times as possible for 1 minute
  8. Drain water from drum
  9. Pour working solution of Kodafix into drum
  10. Turn drum on it’s side to release developer and roll drum back and forth on table for 5 minutes
  11. Hold drum upright over sink to drain
  12. Remove funnel cap (and cup) from drum and throughly rinse film under tap water at sink for 5 minutes (alternatively place film in high volume water bath for 5 minutes)
  13. Hang film to dry

Timed Audio Guide

The above process is nice if you can remember it or read along as you go. For anyone who’s going to be giving it a go in a darkroom with trays (or anyone who just want’s to hear me ad-lib the whole process) I’ve created a timed audio file. You’ll need to start with the working solutions measured out if your using the file with a drum or tank, or already in trays if your going that route. Everyones phone has a voice recorder theses days so you can of course make your own timed audio guide if you’re using a different bunch of chemistry, film, or temperature conditions. That lovely busy-bee sound you hear is me being lazy and using a motor base to do the rolling of the drum.

Play it in your browser above or here’s the link to download as an m4a, and here’s the link to download as an mp3.

Next time: scans of some negatives and notes on my attempts at tray processing. -K

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