The Light Farm


p. 2 — Basics Plus

"In giving detailed instructions for working any photographic process, the description always appears to be more complex than the work actually becomes in practice, and P.O.P. is no exception to this rule. It simply arises from the fact that precautions that would be taken instinctively, almost unconsciously, seem elaborate when described, though when working they are scarcely noticeable. At the same time, it should be recognized that all the precautions advised are essential for the successful working of P.O.P."

The Barnet Book of Photography, edited by W.L.F. Wastell, 1922, p.122



P.O.P. print from c.1910 glass dry plate negative, with assist from Photoshop — 'Baker's Gelatin Chloride P.O.P., TLF Version #1' processed in 'Hypo & Gold P.O.P. Toner/Fixer'


Here's where I could wish for one of those big glass monitor screens popular in science fiction right now. I'd toss a bunch of images up on the board and move them around with a swish of my hand — first comparing one with another and then yet another. Instead, I'll have to ask you to refer back to the quote at the top of page and believe that this is all pretty easy stuff.


Over the last couple of weeks, I have set out to learn as much as I can about one recipe. That has mainly amounted to trying to break it in as many ways as possible! It's been an interesting experience. Up until now, "stress testing" has mostly just happened (i.e., mistakes were made) :-). No need to try to screw up — the boo-boos came fast and furious without any special effort. This time, however, I'm very familiar with the basic (gaslight version) recipe and have had enough experience with other printing-out processes that I was having trouble getting good, new information for TLF. You have to make mistakes in order to learn. (At least, I do.) At a certain point, experience can sabotage the educational mistake-making process. Ergo: stress testing. Bear with me. This is not a linear tale.

I doubt I've covered everything that can go wrong, but I've come up with a good handful. The more basic troubleshooting points are covered extensively in "TLF, Volume 1, The Basics" and here. I highly recommend you look over the information before you go any further. It won't take long, and it could well save you a world of frustration.


Exposure is key, of course. No surprise. Although prints can be exposed by natural light (outdoor, bright, indirect light was always recommended), for most of us, that is impractical. I use a bank of black light UV bulbs in a box with a power switch, made by Edwards Engineering. I've had the box for years, so I'm not completely familiar with the current market. I know that Bostick & Sullivan have a selection of UV exposure units. They're expensive, but I'm sure they are of the highest quality. I know I love my B&S contact printing frame. Easiest of all is to attach a number of florescent bulb fixtures side by side under a wooden table. They can be wired in series with one power switch, or you can just turn them on individually before printing. I imagine any platinum or carbon printing forum could supply all the information needed. One word of caution: to the greatest extent practical, avoid exposing your eyes to the UV light.

Beyond a certain point, increasing exposure does not increase print density. Extreme overexposure essentially bakes the emulsion — think winter skin under a tropical sun. The print here was made with a digital negative (Pictorico OHP). I left a half inch of clear OHP surrounding the negative image. The paper was about a half inch bigger all around than that. OHP blocks a certain about of UV and the emulsion under the negative wasn't badly affected. However, the surrounding paper was overexposed to the point that the density started backing off (solarization). The emulsion frilled and lifted, even into the image area.

It's a balancing act with digital negatives, at least if you leave unprinted film around the negative image. Too little exposure and the paper around the image doesn't reach maximum density. Of course, you can trim a digital negative, but leaving clear OHP (or your digital negative material of choice) around the print serves as a built in "tool" to judge whether or not the density in the shadows of the print image are optimal.

Alternatively, you could trim the print to eliminate the dark border, but I think the surround is beautiful, and again, it acts as an indicator of how well the shadows are exposed.

NOTE: Remember dry-down when you are judging a wet print. A properly exposed print will likely show a line between the area that was under the clear OHP and the area that wasn't. That distinction will disappear when the print is dry. If the crop to the left were wet paper, the difference would look just about like that. When this print was wet, the density difference was much more obvious.


Color Variations with Different Densities
With this recipe there is a subtle, yet distinctive, shift in color from the densest areas to the lightest, even to the extent that the colors used to spot a print should ideally be fine-tuned for the density. I use Marshall's Photo Retouch dyes for my spotting. still carries the full line. Search "products/Retouching-Dyes." Unfortunately, retouch dyes are one of those things that feels like it could disappear at any time.

Spot #1 (deepest density) is a mix of 1 part Verona Brown and 2 parts Basic Violet. Spot #2 is 1:1 Verona Brown and Basic Violet. Spots #3 and 4 are both 2 parts Verona Brown and 1 part Basic Violet, but the dilution increases with decreasing density.

The addition of Raw Sienna to the palette is handy if you are fixing only (no toning), or if your toning tends to reddish.

Practicing is the only real way to learn spotting. A couple of tricks are handy, however. Work as dry as possible. Emulsion lightens when it gets wet and there are subtle color shifts. You may not be matching a color as closely as you hope if you let an area get too wet. If an area does get too wet, it's best to let it dry and then come back to it. Build up color density slowly and then stop short of a "perfect" match. A slightly lighter spotting job disappears. Slightly darker sticks out like a sore thumb.

Color Variations from Emulsion Thickness:
Here's a test I didn't have to find. It found me. It seems that different emulsion thicknesses respond a bit differently to toning. The print above on the left is a tail-end piece of paper. It felt heavier from the start. It's not so thick that it didn't fix out completely, but it did go redder than the print on the right with exactly the same toning routine. The take-home, I think, is that emulsion thickness is a color variable. It's probably not one that can be easily controlled, however. As I mentioned on the last page, I love this basic recipe. The thickness of the emulsion is definitely part of its charm, so when I'm making the gaslight version, I walk right up to the edge of "too thick." It would seem that edge is much further back with the P.O.P. version. It's best to coat warmer and with a smaller gap on the puddle pusher. Emulsion thickness may also be influencing the exact exposures of the different areas of an individual print and therefore influencing the exact colors the toning takes — and 'round she goes.

As thin and even as possible is probably the best bet, but I couldn't pretend to be an expert on "best" where this emulsion is concerned. Different papers will behave differently so it's up to the artist to work out the specifics of his/her materials and workflow. That said, the subtle color differences within even the same portfolio could be seen as part of the art of the medium. The colors are not unrelated and jarring to view. It's hard to tell from a jpeg on a screen, but the light grass behind our reclining couple is almost exactly the same shade in both prints.


I'm going to advocate for digital negatives with this process. There seem to be a number of great reasons. Number one is that most of us have not been making our negatives up until now with a printing-out process in mind. It's nice to be able to pull out old favorites and use them for any process. Two: Many (most?) of us are photo'ing with a digital camera, including phone cameras. The printing output is necessarily digital. Three: Old negatives and plates are likely damaged. Few people have the deep skill required to retouch old materials. In addition, it's hard to justify invasive restoration techniques on precious historical materials. Hopefully, we've outgrown the Indiana Jones philosophy of archeology and history.

Silver gelatin dry plate, c.1910
This plate, purchased in a lot of plates from ebay, is about as typical as they get. It was almost certainly shot by an amateur photographer. The focus is a bit off. All the plates in the lot had the sharpest focus just behind the subjects. The leveling is off, but it's impossible to know if that was an accident or artistic intent. The plate itself is in terrible shape. The emulsion is flaking off on the top, it's scratched, and the silver is tarnished. An absolutely faithful reproduction would take it as-is. Or, we can try to make a print our couple would be happy to have.

(Opinion alert! There are probably as many methods for making digital negatives as there are photographers using them. I share my own only to show how simple the workflow can be — should be, I think. Too mechanical a process diminishes the creative fluidity necessary to thrive spiritually as an artist.)

Scan at 3200 dpi. In Photoshop, rotate, crop, spot, and then do what you like to do to make the nicest, full density range print possible — basically ready for digital output if it were to be the final print. The cropping got rid of most of the area without emulsion. This is often the case because emulsion loss usually starts from the edges of a plate.

Far Left: A straight "invert" of the best print. It is far too light for P.O.P. The digital negative to its right was used for all the prints.

The most straightforward way to increase the density of a negative is in Curves. Pull the 255 point down until the Median number in the Histogram window is "15" (give or take, depending). A test print or two will show you where you might like to do some burning and dodging for detail emphasis, or increase or decrease contrast. You'll probably need to start over from the corrected positive because a P.O.P. digital negative is too dark to easily work on. Take notes on your workflow and you'll very quickly get to know the best parameters for your tools and materials. Curves took the straight invert from Mean: 120.76/Standard Deviation: 51.37/Median: 126 to "19.04/18.12/15." Remember to flip the negative horizontally. I print with a tif file resolution of 720 dpi, and a printer resolution of 2880 x 1440 dpi.

Protecting Digital Negatives:
Circling back to a previous image: As lovely as digital negatives are to work with, they are easily damaged by watercolor paper coated with emulsion. OHP and pigment inks aren't cheap, so best to protect the negatives. Fortunately, this is easy and is a practice borrowed from other processes, especially when protecting original film negatives is vital. Position a piece of very thin mylar between the negative and the paper. One side of a Clear Bags print storage bag is ideal ( I did the comparison testing but I can't even show you. I got careless and didn't note which one was which while I was printing and cannot for the life of me, even with a microscope, tell the difference between protected and bare naked. Protecting the negative eliminates the risk of the kind of damage that is all-too-obvious on the crop to the left.

Digital Negatives from
Digital Cameras:

Theoretically, I suppose, a digital file is a digital file. This is probably increasingly true with increasingly high megapixal cameras. But, is it true with lower resolution files? I haven't gotten around to much phone camera photography yet, mostly because I never remember to take my phone when I go out. One of these days. Until then, the file for this seaweed pic was taken with my first digital camera, a 10 MP Canon Powershot. I'm going out on a limb and assuming it is similar to a current phone camera, maybe not even as good, and it's plenty good. Megapixals don't count for too much with digital negatives and handmade emulsion paper.

I took the file up to a 5" x 7" print. The crops are from that print. The inkjet dots that make up a digital negative are invisible.

I probably end up saying this on every page I write —
the little flecks visible in extreme close-ups are light from the scanner reflecting off the shiny hills and valleys of watercolor paper coated with gelatin emulsion.

They are not visible in an actual print. But, I learned something very useful from my P.O.P. testing.
Below left:"ferrotyped" emulsion. Below right: Naturally dried emulsion.

Hairdryer Ferrotyping:
Ferrotyping used to be a very common way to get a high gloss on baryta paper. RC paper pretty much removed the need for the process. Many years ago, I tried the low-tech method of drying a print on a sheet of glass but I wasn't happy with the results and since high-gloss prints have never held that much appeal to me, I haven't pursued it.

Once again, the old adage — "if you can't be smart, be lucky" — has proven true. In an attempt to rush the dry-down of a test print, I put a hairdryer to a piece of wet P.O.P. (medium heat, at least six inches away from the surface, moving constantly). The print dried to a bright, high gloss. If you have access to an old Kodak paper sampler, it looks for all the world like Kodak Opal Paper L. (This is on Rives BFK.) Room-dried paper looks very much like Kodak Mural Paper R. Interestingly, although the surface is shinier and the texture from the Rives substrate is much more visible with the "ferrotyped" paper, it doesn't seem to catch any reflections from the scanner light. Even if one didn't particularly love the high gloss, it would pay to dry at least one print this way, if only for the ability to scan it without distracting light artifacts. It would make "calls for art" digital submissions much more representative of the actual prints.

One More Thing About Drying:
Aside from the special case of drying the surface of a print with a constantly moving hairdryer while you are holding down the corners to minimize curling, don't try to force print drying with heat beyond that of a warm room. Drying a print too fast makes it want to curl into a tight roll. Once it does that, trying to force the print flat will only bend it. Handmade emulsion coated on flexible watercolor paper won't easily crack like a commercial print can (at least if it hasn't been over-hardened) but the paper will crease and that crease will be visible on the print. If your paper does dry in a tight curl, the best thing to do is submerge it in a generous amount of clean, cool water and let it flatten on its own. Then, re-dry more carefully.

One Last Thing About Processing:
Ease of processing is really where this version of printing-out paper shines. The whole affair takes minimal space and minimal equipment. The emulsion can be made without any lab equipment and one tray can carry a print through every process.

It seems like everyone who ever printed with POP had his or her own method. I've sorted through a number of them and have some pretty firm opinions of my own. Here's my workflow:

Expose the print. Theoretically, you can work by dim room light, but why take the chance on degrading highlights when working by the bright light of cheery, red LED mini-lights is so easy? So, under safelight, take the print out of the printing frame and place it straight into a tray of plain hypo fixing bath. You only need enough to cover the print by about a half inch. If your tray is a close size match for the print (go to your grocery store and buy an assortment of Glad, or Rubbermaid, or cheap store brand plastic food storage containers) you will waste very little chemistry. Gently agitate the print constantly for five minutes. Pour off the hypo. Into the same tray, pour just enough Hypo & Gold toner/fixer to cover the print and gently and constantly agitate that for 10 minutes. Pour off the solution. Into the same tray, pour fresh plain hypo — again, just enough to cover the print. Gently and constantly agitate for five minutes. Pour off the hypo and wash the print in the same tray for two hours by passive washing technique (see "TLF, Volume 1, The Basics", p 85, for more details, if needed). When the washing is complete, remove the print from the water and place it, emulsion side up, on a couple layers of clean paper toweling. Gently run a clean puddle pusher over the surface to remove excess water and lay the print on a clean screen to dry at room temperature. Depending on the humidity, this can take up to half a day.

Because the chemistry is all one-shot, a print at a time can be made. No need to schedule an elaborate or extensive darkroom session. Besides the chemicals needed for the emulsion itself, only sodium thiosulfate ("hypo") and gold chloride are required.

And a Word About the Price of Gold:
The gold turns out not to be as expensive as it might seem. I bought 1 g of gold chloride from Photographers' Formulary for $69. Artcraft Chemicals has it for $45. With it I made 50 ml of 2% gold chloride solution. It only takes 15 ml to make 1 liter of "Hypo & Gold" toner and depending on the size prints you tone and how close a fit your processing tray is, a liter can go a long way. Hypo is inexpensive, so processing chemistry is actually quite economical.

October 17, 2017: A big shout-out of "thanks!" to Arnaud Lesaine for finding a typo. I hate technical typos. I love readers with a careful and critical eye for details who care enough to send feedback. The correct number in the paragraph above is 50 ml, not 500 as originally written. While I was at it, I added information about Artcraft Chemicals. Their chemistry is generally less expensive than Photographers' Formulary.

To be continued...

"Considering the very great number of commercial papers, it will hardly be worth anyone's while to make the emulsion and coat his own paper, save as an experiment. Still, two formulas given in the "Year Book of Photography" will be found very satisfactory."

The Dictionary of Photography, ninth edition, by E.J. Wall, 1912.

The next page will look at one of those recipes and also at gold & ammonium thiocyanate toning. This probably will be a few months away. I have a couple of shows to print for and then some traveling. My best to all. d

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