Now comes the exciting part. We are going to make an image on a negative into the one you've had in your head ever since you clicked the shutter. Only this time, you'll be able to hold it in your hands and share it with the world around you.
To make the print, you'll need one or more sheets of sensitized and thoroughly dried paper (while you are coating, I'd make three to five sheets to experiment with), one 4x5 or larger negative (and only one—just to keep the variables to a minimum), some sort of contact printing frame, a UV light source, and developing/clearing chemistry in plastic print trays. You can buy or make the contact printing frame, the sun is a perfectly fine UV light source, and the chemistry will be included in the Bostick & Sullivan platinum printing kit. That just leaves the trays, which can be purchased from a local photography shop or made from plastic (never metal) storage containers.
A contact printing frame holds the negative and the sensitized paper flat and in close contact with each other. There are several commercially-made frames on the market—Bostick & Sullivan sells one of the nicest, in my opinion. But something as simple as sandwiching the paper and negative between two pieces of glass will also work. If you go the "ready-made" route, get the largest frame you can afford, because pricing isn't all that much different between the larger and smaller sizes, and you'll wish you had a bigger one before you know it.
There are even more possibilities when it comes to UV light sources. Most platinum printers start out using the sun as a light source. Some experienced printers even tout "sunprinting" as a hallmark of their process. But eventually, most folks end up wanting or needing the reliability and repeatability of an artificial light source. With the sun, the amount of UV radiation is constantly changing throughout the day (and for some reason, the sun doesn't work at all at night). So depending on the amount of cloud cover and the time of day, printing times can vary considerably, and depending on the time of year, it may be unbearably hot or cold outside. That said, working between 10:00a.m. and 2:00p.m. on mostly sunny days will allow reasonably short exposure times and fairly consistent printing from spring through fall.
But what if you could bottle the sun and bring it inside? Well, you can with one of the various electrically powered UV light sources on the market. That blacklight you had in college is one way. Fluorescent UV light sources are relatively inexpensive to purchase and operate, don't generate much heat, and are kind to your electric bill. They can be purchased from specialty suppliers or built from parts bought at your local home center. Fluorescent units should be turned on to "warm-up" a few minutes before your printing session and left on for the duration of the session. Also, "middle-aged" fluorescent tubes work better than new or old ones, so you'll need to keep an eye on exposure times with both a new setup and one whose tubes have several thousand hours of operation behind them.
Another option (one that I haven't used) is incandescent photoflood bulbs, available from photography stores and specialty bulb suppliers. Photofloods are usually suspended from the ceiling under a metal reflector and rigged to raise and lower. From what I understand, they are inexpensive but very short lived and run hot but give reasonable exposure times. Feel free to give them a try and let me know.
The third option is the one I use most often—a printshop "plate burner." Plate burners are used to expose sensitized printing plates to UV light in the photoengraving process and come in a variety of shapes and sizes. In addition to a high-powered light source, most include a vacuum-operated contact printing frame, which is used in place of the "manual" frame mentioned above. Most also have built-in integrators, which allow a specific exposure to be set and compensate for output changes over the life of the plate burner bulb (a high-output arc lamp). Although plate burners sell for thousands of dollars when new, so many printshops are going digital that like new units can be found at online auction sites for a song. I paid just US$28 for one with all the bells and whistles, but be prepared to deal with a freight company for shipping—plate burners are large (roughly 36 inches wide, 36 inches deep, and up to 72 inches tall) and heavy (150+ pounds). Also, you will need at least 15-amp, 120-volt electrical service to run one.
Before you start printing, you'll need to set up all your chemistry in some sort of trays for sequential processing. The trays should be plastic, and I don't recommend reusing trays that have had silver or other photographic materials processed in them. I'd also recommend trays that are at least 16 inches by 20 inches, even if you only plan to do 4x5 work (you might want to get one 8x10 tray for the developer step, though). You might never go bigger than 4x5 photography, but you will eventually want to make a larger print with multiple negatives, and you'll be in for a great big dope-slap when you only have small trays. For really big prints I bought plastic under-bed storage boxes that are almost three feet long, but you probably don't need to go quite that large in the beginning.
Before you even pull out the printing frame, mix up the chemistry that came in the platinum printing kit. The developer, ammonium citrate, comes in crystalline form, packaged in a one-liter plastic bottle. Add all the crystals to 100ml to 200ml of warm (around 100°F or 20°C) distilled water and stir until dissolved into a syrupy liquid. Then add more distilled water to make one liter of solution. The clearing agent in the kit is EDTA, a common food additive. It should be mixed at a rate of around four tablespoons (¼ cup or 60 milliliters volume) per gallon (about four liters) of water. I just use tap water for this, but if you have really bad tap water, use distilled. You'll be using the full liter of developer—don't worry, it will be reused over and over in later printing sessions, so don't toss the plastic bottle it arrived in—and you'll need enough of the EDTA solution to fill three trays about two inches deep (16x20 trays take about a gallon each).
When I'm setting up printing trays, I try to put them in logical order. First is the tray for the developer, followed by a tray filled with plain tap water. Then, there are the three clearing trays, all preferably white, so you can see when the clearing solution starts to get dirty. Finally, I set up a wash tray at the sink and have it overflowing with a small, continuous stream of water for the final wash. Fill all the trays, except the one for the developer, now. This would also be a good time to turn on the fluorescent UV source, if you are using one, to let it warm up and stabilize. The sun or a plate burner shouldn't need to warm up.
Next, clean the glass on your printing frame and load the negative and paper. If you're using a standard printing frame, open the back and place the negative against the frame's glass front, emulsion side up (facing toward you). Then, place the sensitized side of the paper down, against the emulsion side of the film, and close the back. With a vacuum frame on a plate burner, do almost the exact opposite. Place the paper, sensitized side up, on the platen, place the negative emulsion side down onto the sensitized side of the paper, close the glass top, and start the vacuum pump.
Most of my negatives print on my standard coating in about five or six minutes in full spring or fall sun, under my fluorescent tube bank, and on my plate burner. Yours will probably take about the same amount of time, unless you are using a thin, silver printing negative. Your first prints will set the baseline for all of your variables, and rather than making a bunch of test individual prints, a quicker, less expensive way to get there is to step the exposure across a single print. Cut a piece of cardboard or very heavy paper large enough to cover all but about one inch of the length of your 4x5 negative and attach it to the glass over the negative. Expose that one-inch strip for one minute and slide the cardboard down to expose two inches. After one more minute of exposure, slide the cardboard down another inch and repeat until the entire negative is uncovered. At that point, expose the entire image for another three minutes. The paper will then have strips that were exposed for three, four, five, six, and seven minutes.
Some platinum printers, Arentz included, recommend inspecting the print's progress as the exposure moves along. This is all but impossible on a vacuum frame, and I never could tell much about the state of the print by opening my split-back frame and observing the faint printing out image that appears over time. The step method works much better for me, and it takes only one or two prints to nail down your own printing parameters.
Ok, here's the part we've all been anxiously awaiting...
Remove the exposed paper from the printing frame and place it face-up in the developer tray. Then, rapidly pour the developer over the print, wetting all of the paper. And BAM! There's your image, all at once. Silver printers will be especially surprised to see the image appear so suddenly, instead of gradually over a minute or so.
Let the paper soak for a minute or two to make sure development has gone as far as it will, drain the print fairly well by holding it by one corner over the developer tray until the stream of developer turns to drips, and transfer the print to the water tray next to the developer tray. You can use gloves to move the prints around, but this chemistry is benign enough that I just use my hands (chapped hands at the end of a long printing session). But whatever you do, don't use tongs—they will tear the wet paper.
After a quick dunk and agitation in water tray, drain the wash water off (as above), move the print to the first clearing tray, and let it soak for about five minutes, agitating occasionally. The paper will try to float in the clearing bath until it is saturated, so gently push it back down when it rises to the top. Follow the first clearing bath with five minutes in each of the next two clearing trays. Then move the print into the running water tray to wash for five to fifteen minutes.
You now have a print, but its appearance will change considerably upon drying. Platinum prints will dry-down a good deal darker than they look fresh from the wash. They'll end up looking approximately the way they do when submerged under an inch or so of well used developer, so developing will give you a good idea of the finished print's appearance once your developer has aged to a deep yellow-brown.
The wet prints should be dried face-up on plastic window screen material or in a print dryer. I air dry using sliding replacement window screens from the home center. Each holds two of my 8x10 prints. When they dry, the prints will curl to some extent, so they must be pressed flat before mounting and framing. I interleave the prints between sheets of blotter paper and crank down the stack in my home-built press for a day or two. Another option is to use sink cutouts from countertops (available from plumbers and cabinetmakers) weighted down with canned goods, bricks, or whatever you happen to have on hand. I recommend against using a heated press, because it can damage the paper (or other) substrate.
Note: You don't have to press the prints to evaluate them—just make sure they are thoroughly dry first, because they will darken over time as they continue to dry.
First, do not throw out that used developer! Like a fine wine, it gets better with age. Simply funnel it back into the one-liter bottle it came in and you're ready to go for the next session. I usually mix a couple of gallons at once and work with one only one of them. At the end of a printing session, I pour the used developer back into its storage container and top it back up to one full gallon with some of the unused developer. Also, try to clean up any developer spills or drips when they happen. If left to dry, they will become either hard encrustations, gooey blobs, or crystals that go everywhere.
The used clearing bath can go down the drain when you are done. If you are making a long run of prints, you may need to change out one or more of the clearing baths during the run. To make most efficient use of the clearing chemistry, clear prints until the first clearing bath is noticeably stained. Empty that bath and refill it with fresh clearing agent. Then, move the second bath into the first position, the third bath into the second position, and the new bath into the third position. This ensures the last clearing bath will always be nearly untainted and the first bath will still be capable of doing its job.
In addition to the developing/clearing chemicals we covered above, there are also others that will do the same job. The most common (and probably the oldest still used) developer for platinum is potassium oxalate, and I now use sodium citrate, instead of ammonium citrate, to give my prints warmer tones. I haven't, however, tried potassium oxalate because it is much more toxic than either of the citrates. Any number of acids can be used for clearing, but again, I chose to stick with the relatively benign EDTA. Several texts, including Arentz's, cover your many and varied options for platinum developers and clearing agents, and I recommend reading one or more of these fine dissertations before you start to experiment.
In the above instructions, we were using fresh, roughly room temperature developer. But by varying the temperature and/or makeup of the developer, we can also change the tone of the print. Generally, warmer developer will bring out warmer tones. In addition, used developer with more palladium dissolved in it will give warmer blacks than developer with more platinum. By using different developers at different temperatures and with different "contaminants," we can make prints that vary in tone from rich brown-blacks to cold, metallic blue-blacks.
When working with any UV light source, be sure to take proper precautions. In fact, I'm more concerned about UV exposure than working with any of the chemicals I use. It can lead to cataracts, skin cancer, and even a nasty sunburn. You should never look directly into a UV light source, and 100% UV-blocking sunglasses or safety glasses are always a good idea. I have surrounded my plate burner with a sheet of smoke colored, plastic welder's curtain to block most of the UV radiation from escaping, but I still try to stay out of the room when it is running.
Finally, you should follow the same precautions during developing and clearing as you did in the coating process. Don't eat, drink, or smoke; wash your hands frequently; and avoid inhailing or otherwise ingesting dust from the dry chemicals or fumes from their liquid counterparts. None of the components of the chemistry I use is particularly harmful (except the metals in used developer), but you should still practice reasonable lab hygene. However, some of the alternative chemical compounds that can be used in platinum printing are highly toxic and demand a much greater level of respect. Please keep that in mind if you decide to experiment with other developers and/or clearing agents.