Most people do not have a permanently installed darkroom space. If you are fortunate enough to own a house or an apartment with the appropriate space and configuration and can dedicate an entire room, walk-in closet or “the room under the stairs” to printing, you are ahead of the game. However, like most of us, you are probably printing in a makeshift kitchen, bathroom or smaller closet.
For those who can allot the space for it, a sink keeps all the mess in one permanently enclosed and washable space. Inexpensive sinks are made of ABS plastic or fiberglass, while high-end professional ones are made from stainless steel. The ABS sinks work fine and will save you a lot of money. Stainless steel ones are more expensive and much heavier, but will neither stain nor warp. If your space is unusual, you can even have a steel sink made to order.
There are many sink designs to choose from. Some have drains in the center, others have them off to one side, and others have no drain at all. Some have a standpipe that can be used to turn the sink into a water bath. You can also buy a temperature-regulated sink, which is a sink with a built-in thermometer. Backsplashes and plumbing accessories are normally not included with a sink and should be considered. Sinks must be plumbed in, and unless you are familiar with basic premises of plumbing, the cost of a plumber must be factored in.
If possible, and if the space is there, it is best to get a sink that is bigger than you think you'll need. This is a case where bigger is better. An ideal sink should hold at least four or five trays of the largest size print you'll want to make (Develop/Stop/Fix/Hypo Clear/Holding Tray and Wash). The trays themselves should be deep enough to contain chemicals without sloshing over the top. For more information on developing trays, please see the B&H InDepth article, Darkroom: Storage Bottles, Graduates,Trays and Tongs.
A water temperature control unit can be very useful when mixing chemistry or processing film. Film emulsions are sensitive to gross time and temperature changes. Isn't it always the case that just when you are processing your negatives, the person upstairs flushes the toilet and the water temperature spikes? A panel regulates your temperature and keeps your water at a constant temperature, facilitating consistent processing. Traditionally, control panels are mounted on a wall over the sink where they can be reached easily. Some have a built-in flow meter, water filter and multiple filters.
Temperature is adjusted via a dial that controls a sweep hand on a gauge. Some plumbing may be required to attach it to your main water supply. Generally, these connections are not difficult to make. The panels themselves usually accept standard couplings.
In the absence of a water-control panel, a good quality photographic thermometer is desirable. If you want good negatives and prints, knowing the correct temperature of your chemistry is mandatory, since most chemistry requires a specific temperature/time ratio to operate at peak performance.
Stainless steel stem thermometers with large dials are easier to read than smaller glass models. The small glass ones are good for tray processing. You can also buy an adapter that fits on the spigot of a faucet and has a slot for a thermometer. As you manipulate the hot and cold valves, you will see the thermometer respond accordingly.
Water filters are invaluable, particularly if you live in a large city. They can save you hours of aggravation and retouching. Inevitably, small particles of dirt creep into the water supply and contaminate your chemistry. This translates into particulate matter that clings to negatives and encourages uneven development. The more the chemistry is distributed evenly over your negative, the more even the tonal range of your negative will be. All it takes is one horrendous water mark or dust particle to ruin a negative.
Filter strength is usually measured in microns, with a 5-micron filter being more effective than a 10-micron filter. The smaller the micron rating in your filter, the more junk is filtered out of the water flow. Some filters come in durable plastic housings that can be screwed to a wall or mounted to a water-control panel, which is a control center for water flow and temperature regulation. Make sure you buy the right filter, either for cold or hot water. There are panels that contain one of each filter with an additional control for temperature. Small, inexpensive filters come in a simple plastic housing and are generally not rated for higher temperatures.
The fact is anything that you put between the water supply and the negative to cleanse the water is a good thing. Finally, the filter should be placed in a convenient location where the old filter can be periodically changed. As a rule of thumb, filters should be changed on a regular basis, either when you notice the filter is excessively dirty or when there is a noticeable slowdown in the water flow.