Like any other undertaking, platinum printmaking requires at least a minimal investment in tools and workspace. However, you don’t have to have the best of everything to begin, or even the best of everything to make wonderful platinum prints. In fact, many tools can be improvised, and workspace requirements aren’t nearly so restrictive as those for modern silver-based printing. But there are some requirements that cannot be worked around. You must have access to a relatively large negative image that fits the platinum printing profile. You must have a suitable workspace to prevent contamination of living areas with potentially toxic chemicals. And you must have basic tools for making a large negative, coating printing paper, and developing and finishing your prints. I do all of the above in a typical suburban home, so you should be able to do the same with only a small amount of planning and preparation.
When I began printing in platinum, I had a leg up because I was already shooting with large format equipment—8x10 and 4x5 cameras. (For those unfamiliar with large format gear, an 8x10 camera, for example, can make an image on sheets of film as large as approximately eight inches by ten inches.) Platinum and most other alternative processes use ultraviolet (UV) light to expose photosensitive materials, meaning traditional photographic enlargers can't be used to make a large print from a small original image on film. Instead, a large negative is placed in contact with the sensitized paper (or whatever is used as a support) and a UV light source—anything from the sun to powerful, specialized (and expensive) arc lamps—exposes the paper through the negative. The resulting printed image is the same size as the negative image.
Images as small as those captured with a medium format (2¼-inch x 2¼-inch or 6cm x 6cm) camera can be used for platinum printing. These small images are actually quite beautiful, provided the appropriate subject matter is chosen. Typical 35mm images are all but out of the question from the standpoint of attempting both to make a good print and to view the finished print. An image on 35mm film is simply too tiny to really evaluate with the unaided eye. But that's not to say someone hasn't or won't find a place for such miniscule images (maybe hanging a loupe on each frame or making a larger printed image from multiple 35mm frames would work). I tend toward the larger is better school of thought, myself, but I haven't yet run out to buy a 20x24 camera.
A good starting point for working with platinum prints is a used 4x5 camera, but be forewarned, a decent lens/shutter combo can cost more than the camera. The 4x5 image size is the most popular among large format photographers, so cameras, lenses, and film are all easy to find. It is also large enough to make a platinum print even us old folks can see.
A less expensive alternative would be to acquire a 4x5 pinhole camera. Pinhole cameras use a tiny hole pierced in metal shim stock in the place of a glass or plastic lens to focus light onto the film. A properly sized pinhole will yield a surprisingly sharp image—sharper than some glass lenses—but you loose control over lens movements and depth of field that you'd normally have with a large format camera, and exposure times will be much longer than those with a glass lens. Of course, you could always fit a bellows-type camera with a pinhole lens to regain some amount of control and save the cost of a glass lens and shutter.
A nicely made, new 4x5 pinhole camera can be had for around US$100. A used 4x5 field camera in good working order will run US$300 to US$600 on eBay, and a used "normal" lens (~150mm) with shutter shouldn't cost more than US$300. For those with more time than money or a do-it-yourself attitude, pinhole cameras are simple to make, and even building a view camera isn't out of the question. You'll also need a few 4x5 sheet film holders, whichever way you go. Light tight, modern, plastic 4x5 film holders commonly sell for around US$10 each on eBay.
Even though I don't use them, there are also several options, other than shooting directly onto large format film, for making a negative large enough for contact printing. The time-honored way is to use an enlarger to make either a direct positive image (a positive of a negative is a negative) or an internegative (a large positive image on film—a negative of a negative—that's used to contact print a large negative) on film especially designed for this purpose. The thoroughly modern way is to either scan a smaller film image or use a digitally captured image to print a large, computer-generated negative image onto transparency film. Finally, the oldest method is to use an enlarged negative image printed on paper that has been oiled to make it transparent enough for light to penetrate. At some point, I'm sure I'll end up trying one or another of these, but for the time being, I'm content to made large negatives in camera. However, any of them are certainly viable alternatives to investing in large format gear when the photographer is already set up to work with smaller format or digital equipment.
I have currently standardized on Kodak T-MAX 400 (TMY) for my film needs. I say "currently" because I had, for many years, used T-MAX 100 (TMX) as my standard film stock. However, Kodak abruptly and without notice changed the formulation of its 8x10 TMX (but not the 4x5 version, as far as I know), adding UV inhibitors. I happened to discover this fact when a batch of normal looking negatives took much more exposure to print and yielded images with lower apparent contrast than expected. My affinity for T-MAX film goes back to my 35mm days, and except for the issue mentioned above, its working characteristics are particularly well-suited to platinum printing. That said, there are quite a few readily-available black and white films that are perfectly acceptable for platinum work. Just pick one and learn to take advantage of its unique personality.
Sheet film has one distinct advantage over the roll film commonly used in smaller cameras (other than image size, of course). Each sheet of film can be developed individually to suit both the scene that was being photographed and the print to be made. In contrast, all the images on a roll of film generally have to be developed at the same happy medium, regardless the individual images' requirements. Specific development allows the photographer to vary effective film speed with every shot and selectively control the image's overall density range, from the lightest areas of image detail to the darkest. The film's exposure determines the darkest areas of a given scene that will record details, and its development is used to expand or compress the image's density range to complement that of the desired print.
Like many field photographers of old, my "darkroom" is portable. That wasn't a choice to be true to my craft's roots, by the way, but a necessity. Currently, I don't have the space to build a dedicated darkroom, so a large film changing tent suffices when absolute darkness is required. I use it to load and unload film holders, as well as load exposed film into daylight development tanks. Other than those operations, I can do everything else under normal room lighting. In short, a darkroom would be nice, but it is certainly not required for platinum printing. Modern silver printing, however, would not be possible in my situation. Or it would, at the very least, be quite the feat to cram an enlarger and print development trays into a changing tent.
I have divided my workspace into two distinct areas—"wet" and "dry"—as is standard practice in most photographers' studios. Anything in the wet workspace is, of course, subject to getting wet, so nothing goes into the wet area that I don't plan on wetting with water or chemistry. Conversely, the dry workspace is protected from almost anything wet. If it can drip or splash or leak, I try to keep it out of the dry workspace.
My wet workspace consists of a small guest bathroom and my kitchen. Both have running water and are designed to withstand getting wet (as do/are, I suppose, most kitchens and bathrooms). Exposed film is processed on a Jobo CPP-2 rotary processor, and I develop, clear, and wash prints in large trays. The biggest benefit of my improvised wet space is that I'm more careful with chemistry and more fastidious about cleanup than some folks I've known who have dedicated darkrooms. Its main drawback is that I have to completely set up before and tear down after every wet session.
What I lack in a dedicated wet workspace, I managed to make up for in my dry workspace. An extra bedroom was converted for the cause by clearing everything out (except, unfortunately, the cats' litterbox) and adding storage and work surfaces. I started by building two six-drawer flat files large enough to hold uncut sheets of mat board and printing paper. On top of one, I placed a sheet of 3/8-inch glass to protect the wood underneath and provide a smooth, dead flat surface for coating paper. I also built a press for flattening finished prints and a light table for working with negatives and masking film. Rounding things out are some wall-mounted shelves, a tall "baker's rack" style shelving unit, and printshop plate burner. The only exception to my wet/dry space divide is that I do store mixed chemistry in the dry space, but I take care that nothing can spill onto anything important.