Automatic Temperature Regulation
Chemical Storage and Waste Disposal
Most beginning photographers start by putting trays of chemicals on the kitchen table or counters. They soon learn that spills are impossible to avoid and temperatures in the trays difficult to hold at a constant level. In addition, the cleanup time is longer than need be because of the care with which the counters and tables have to be cleaned. The solution is a sink large enough to hold all of the processing trays. Photographic sinks should have a large area and a shallow depth. They can be equipped with temperature control faucets, standpipes, and duck-boards to make them even more efficient. You can build your own of wood, as shown in Chapter 6, but commercial models are available that are perfect for the home darkroom.
Commercial sinks come in either plastic or stainless steel models. Stainless is extremely long-lasting but much more expensive. Stainless sinks also tend to be a little noisy with trays and tongs banging against them, but their durability and ease of cleaning make them a dream to use. Plastic sinks are equally efficient at keeping the spills contained, are easy to clean, and, given reasonable care, should outlast even the youngest photographer. Sinks can be ordered from suppliers either with or without stands. The stands make them portable if you are moving. They can also be built in without using the stand, but in doing so you are making it much more difficult to remove and install in another location. Be sure the stand is made of a corrosion-proof material or is well painted; the chemicals used in photography will badly corrode most steel stands, and rust scaling will detract from the cleanliness and appearance of the room.
Note the sink sprayer that makes cleaning up easy. This device can be installed on any sink, including one you build yourself.
Water quality in this section refers to everything but its temperature, which is discussed in the next section on temperature regulation. There are several basic components that affect the quality of water used in photography.
These small, solid particles exist in all water systems. They originate at the source, or enter into the water at some point in the distribution system, and can be removed by using water filters. Their removal becomes increasingly important if you are using a temperature-regulating valve that can be damaged by solid particles in the water.
Although these particles have relatively little effect on prints, they have a tendency to adhere to negatives, and once they have dried to the surface, it is impossible to remove them.
Hard water can make chemical mixing difficult, and soft water can soften the gelatin on film and paper after long washing cycles. The range of allowable hardness of water is from 40 to 150 parts of calcium carbonate (CaCO3) per million. To find out the range of your own supply, call the local water authority.
Only a very expensive filtration system can remove anything but suspended particles. For badly polluted sources, one solution is to use distilled water, at least for washing the negatives. You can store water that runs off of the air conditioner or dehumidifier cooling coils. Because of concern with water quality, it is possible to buy very inexpensive distilled water at your local market. This water is sometimes labeled infant or baby water. However, if there is plain distilled water, it is the same thing and a bit less expensive.
Air in water and solutions causes bubbles to build up on film and paper surfaces, preventing developers and other chemicals from coming in contact. This should be prevented if uniform development, fixing, toning, and washing is to be achieved. Either boil the water to drive off the air, or add an aerator to the incoming line. The aerator forces large bubbles into the water, and these combine with and remove the smaller ones before rising to the surface.
When stirring chemicals, it also helps to use a stirring paddle with a wide blade and narrow handle. The narrow handle disturbs the surface of the solution less than a larger object would and prevents additional air from entering. Some chemical mixers are designed to go one step further and are magnetically operated paddles without handles so very little surface disturbance occurs.
If you are using water from a source other than a municipal water supply, you should have it analyzed by a lab to determine its contents. The following table gives some of the maximum allowable limits for commonly encountered chemicals.
Practical Limits for Common Impurities in Water Used for Photographic Processing
Impurity | Maximum or Range or Content (ppm*) |
Color and suspended matter | None |
Dissolved solids | 250 |
Silica | 20 |
PH | 7.0 to 8.5 |
Hardness, as calcium carbonate | 40 (preferable) to 150 |
Copper, iron, manganese (each) | 0.1 |
Chlorine, as free hypochlorous acid | 2 |
Chloride (for black-and-white reversal) | 25 |
Chloride (for color processing) | 100 |
Bicarbonate | 150 |
Sulfate | 200 |
Sulfide | 0.1 |
*parts per million | © Eastman Kodak Company 1967, 1974 |
Water filters come in cold or hot models. The basic difference is their respective ability to resist temperature damage. The hot-line filter is usually designed to withstand high temperature and pressure over a sustained period of time. The cold filters are not subjected to this stress, so their quality (and price) is not as high.
This illustration shows a Leedal model and the filter element inside.
The more heat you have in photographic processes, the faster things happen. It is easy to understand the importance of temperature regulation in controlling the rates of chemical reactions found in developing, fixing, toning, and washing. As a rule of thumb, a 10°F change in temperature will double or halve the rate of a chemical reaction. Solution temperatures can be regulated in several ways to ensure that processes occur at expected rates and can be repeated.
Having the room temperature close to the temperature at which chemicals are used helps reduce the need for more exotic controls. It is not necessary to make conditions perfect, but perfect conditions can save a great deal of time, because if stored chemicals are at the correct temperature, they can then be used without additional heating or cooling.
When mixing chemicals, washing prints, or trying to maintain a constant temperature in a water bath, it helps to have a thermostatically controlled water valve. These can be preset to maintain a temperature within a given design range (usually 1/2°), despite changes in line temperature or pressure. They are a good investment and significantly reduce the problems involved with working in a darkroom.
Chemicals can be maintained at the proper working temperature by immersing the container in which they are held in a water bath that is maintained at the correct temperature. The larger volume of the water bath makes the temperature more stable and will keep the smaller volume of chemical solutions from changing temperature. A water bath can be made by immersing a tray or tank in a larger one into which water at the correct temperature has been poured. The larger the amount of water in the bath, the easier it is to obtain and control a stable temperature. If you have a sink, it can be plugged with a standpipe that you can buy or make out of a plastic graduate. The standpipe will allow the water in the sink to rise only to the top of the pipe, at which point it overflows into it and down the drain. The large volume of water in the sink will maintain a stable temperature for a longer period of time.
In the absence of a temperature-regulating valve and standpipe, the water bath temperature can be maintained with either an immersion heater or recirculating unit. The temperature can also be controlled by adding hot or cold water occasionally to raise or lower the temperature.
It helps to have a stainless steel graduate to use for changing the temperature of small volumes of chemicals. Stainless steel is an excellent conductor of heat, and immersing it, full of the chemical, into a hot or cold bath will quickly change the temperature of the solution it contains. The same effect can be obtained with a plastic graduate, but it takes much longer to obtain the same degree of change.
Temperature regulation of the water in most darkrooms will depend to a large degree on the amount of hot water available to your house or apartment. You may well find after spending $300 on a temperature-regulating valve that your hot water capacity is sufficient for only half an hour or so of water at the desired temperature. It’s better to know beforehand what the capacity of your heater is, what your consumption is expected to be, and how the two relate. If you have to install a larger hot water heater for the darkroom, you can derive a side benefit (the whole family can take long, hot baths one after the other).
For photographers who spend a great deal of time in the darkroom, one of the main problems is regulating the temperature of the water flow into water baths and print and negative washers. It is a great luxury to be able to avoid constantly monitoring and adjusting the temperature of the incoming water. Manufacturers have developed a number of units that reduce or remove this onerous chore; this section illustrates and describes some of the most popular ones.
When it comes time to order the temperature regulator for your sink you will have to specify the flow rate at which the temperature-regulating valve will normally operate. This allows the supplier to install a collar that will allow you to use the temperature-regulating valve without having the water on full force. Measuring the flow rate is a simple matter.
Find a five-gallon can and connect it to a sink outlet with a rubber hose. Turn the water on at the flow rate you intend to use. Time how long it takes for the five-gallon can to fill. Divide that time by 5 and you will have the gallons-per-minute flow rate you will be using.
The flow rate will vary seasonally, with the lowest rate likely to occur in the hot summer months when neighbors are watering their lawns and filling their pools. This should be taken into consideration when measuring the rate of flow.
Most well-made units have a vacuum breaker that prevents the siphonage of water back into the water supply system. In many areas this is required by building codes.
Because most units operate best at their maximum rated capacity, it’s important that you determine the flow rates you will be dealing with and notify the company from which you are buying what range you expect from their valve. For most home darkrooms, a flow rate from 1/2 to 2 gallons per minute will suffice for all operations, including washing.
A thermostatic mixing valve requires a sufficient difference between hot and cold supply lines to operate accurately. So if you are considering installing one of these valves in areas of the country where the cold water is above 60°, you may find that the mixing valve will not work without the installation of a water chiller. Check this with both your water department (they can tell you the highest temperature to expect) and the manufacturer of the valve and chilling unit This unit is from California Stainless.
It’s been said that all Edward Weston had in his darkroom were a light-bulb, a printing frame, and three wooden developing trays. This indicates either the importance of trays or the lack of importance of everything else. The primary function of trays is to hold chemicals, but variations in design, materials, and purpose do affect, slightly, the usefulness of the various models.
The trays should be deep enough to prevent unwanted overflow when agitating the tray full of chemicals. And they should be large enough to handle a print easily, either by hand or by tongs, without trapping the print between sides that are too close together. Ribs on the bottom reinforce the tray and also make picking up prints easier.
Inexpensive trays can be too small to hold the sized prints for which they are marked. Rather than buy a more expensive tray, however, you can buy the larger size of the less expensive one and save some money.
A tray should be rigid enough so that you can lift it when full of chemicals without it bending under the weight and spilling chemicals. Try flexing the tray by holding the corners and twisting. If there is too much flex, buy another model.
To reduce the possibility of tray contamination, label the trays for developer, stop bath, and fixer and then use the same tray for each chemical every time. Use entirely separate trays for such things as toning solutions.
Just as the kitchen of a good French chef is made more enjoyable and more productive as a result of high-quality and useful accessories, so is the darkroom. Not having a graduate large enough to mix a solution, or a stirring rod long enough to keep your hands out of the solution when mixing, are frustrations that can and should be avoided. These pages describe some of the accessories that are available and what questions to consider when buying them.
When buying a paddle, make sure that the handle is long enough to provide you with a grip when fully immersed in the largest mixing container you use.
A tall, thin graduate is also useful for measuring small quantities of chemicals. Trying to measure I ounce of stop bath concentrate to mix with I gallon of water is very difficult with a large, wide graduate.
Thermometers can be divided into classes based on the principles by which they operate. Your selection should be based on accuracy, cost, and durability.
Liquid in Glass. This type is identical in principle to the thermometers that we take our own temperatures with. It consists of a bulb full of a fluid, usually alcohol, and a long narrow tube marked in degrees. As the fluid heats or cools, it either expands or contracts.
These thermometers are extremely accurate, relatively fast-acting and long-lasting—if you don’t break them. If the thermometer overheats, you may break the tube. To work accurately, the entire column of liquid that indicates the temperature should be immersed in the liquid you are measuring.
Liquid in Glass with Metal Backing. Some thermometers are reinforced with a metal backing to prevent them from rolling or breaking as easily. These are ideal for tray thermometers, but if the scale is on the backing and not on the tube itself, the thermometer can get out of register and indicate the incorrect temperature.
Dial Thermometer. These thermometers have large dial faces that are very easy to read. The needle moves because of the expansion or contraction of a bi-metallic strip. These thermometers are also quite accurate and durable but, because of their mechanical nature, are more sensitive to physical abuse. If a glass thermometer breaks you will know it, but if one of these does you may not. The dial face is also prone to leaking, because the seal between the glass and metal case will not last forever. Occasionally calibrate them by comparing with a thermometer that is known to be accurate.
Electronic Thermometers. These thermometers are available with digital readouts and even audible ones. It is sometimes difficult to read the temperature on a glass or dial thermometer because of parallax and the small numbering on the thermometer itself. This problem is eliminated with the digital thermometer that gives you a direct numerical readout of the temperature. However, they are sensitive to mechanical damage and moisture because of their electronic nature.
Photographers using 35mm or 2 1/4 format film are confronted with the difficulties of developing a long strip of film. The most common solution is to coil it on a reel so that there is sufficient space between the surfaces to allow for the circulation of chemicals, but not so much that the coil occupies a large space. This basic principle is packaged today in three variations: stainless steel tanks and reels, plastic tanks and reels, and a combination of stainless steel tanks with plastic tops. Traditionally, most pros have used the all-stainless-steel tanks and reels because they perform extremely well and last almost forever. However, one problem is that they may leak around the top if the tank is inverted during agitation. This difficulty has been solved by marrying a plastic top to the stainless steel tank. The seal is tighter and less susceptible to leaks. Many photographers use the all-plastic tank and reel, which has the advantage of a reel that can be widened or narrowed depending on the film format you happen to be using. With the stainless steel reels, you will need a set for each format you shoot.
Stainless steel tanks will lose or gain heat more quickly because of the conductivity of stainless steel, so if the room is a good deal hotter or colder than the chemical solution, use either a water bath or change to plastic tanks that will act as an insulator.
The long rod is used to raise and lower the reels. Always buy enough reels to fill the tank and use them all if you are developing one roll of film and you agitate by inverting the tank. If one reel slides up and down the tank, development will be affected because of the increased agitation.
Each reel holds 6 sheets of 4 × 5 film. Two reels can be used with the tank to make roomlight processing of up to 12 sheets of film as convenient as processing roll film. Also, this economical daylight system uses only half of the chemistry required for processing in hard-rubber tanks.
The washing of prints and negatives is absolutely essential if they are expected to last. Many photographers are careless with this step, not fully realizing that the effects of poor washing may arise days or years after the processing. Prints and negatives that are not fully washed of chemicals deteriorate and, unfortunately, contaminate other prints and negatives with which they come into contact. If a poorly washed print is placed on a drying screen or run through an electric dryer, that screen or dryer is contaminated and will affect the prints that follow. There is no excuse for not washing well—it is the one unforgivable sin of photography.
The quality of the washing depends on the number of complete water changes in a water cycle.
To be effective, wash water must circulate on all sides of a negative or print. Its failure to do so will leave spots that continue to be contaminated even when the rest of the print or negative is safe. Just laying prints in a tray with a hose circulating water over them is not enough. The flow must be enough to change all of the water in the washer at least five times.
Leaving the reels in the developing tank and running water in the top does not provide for even washing of the negatives. The water tends to wash those at the top faster than it washes the ones at the bottom, and because the film is in a coil, the water flow will not be evenly distributed along the film but will tend to wash better in the direct stream from the faucet. To compensate for this, several new washers have been developed to ensure that the water is evenly distributed throughout the tank, and that heavy chemicals do not rest on the bottom of the tank as they would if water were poured in from the top.
The key ingredients in good print washing are to keep the prints separated so that wash water can freely circulate around them, and to follow the paper manufacturer’s directions regarding the time they should be washed. To shorten washing times, you can use Hypo Clearing Agent made by Kodak or PermaWash manufactured by Heico.
Washing prints for archival purposes is not an easy task. Maintaining an adequate rate of flow and keeping the photographs separated are not enough to ensure complete washing. The dynamics of fluid flow (that is, the wash water) depend on several factors; the placement and orientation of prints in a washer can affect the flow. If all of the prints are horizontal, they can have air pockets or pockets of low water flow regardless of how high the water flow is elsewhere in the washer. To be absolutely safe, buy a washer designed for archival purposes and follow instructions.
To be washed effectively, prints should be placed in a tray twice their size. This allows the water coming from the siphon to spin the prints and gives them much needed agitation.
Electronic sophistication is affecting traditional darkroom equipment primarily in the design of exposure meters and timers. In most cases, the absolute accuracy of many of the newer units is not necessary; what is necessary is that your timer repeat each timing cycle exactly the same as every other. If the timer takes 65 seconds to indicate a minute, that’s okay, as long as it does it every time. The only exception to this rule is when you are working with color materials that are much more sensitive to the absolute timing of processes.
Timers can be broken down into two main classes, mechanical and electric. Mechanical timers are operated by winding a spring; electrical timers require a source of energy from either a wall outlet or a battery. Electric timers can use either motors or transistors. Electronic timers will often have a digital readout.
The old standby in most darkrooms is the Gralab timer, which is used for timing everything from development, to printing, to making coffee. Its timing range from 1 second to 1 hour makes it useful for timing many activities. Many of the newer timers now on the market are designed for specific purposes and should be used only for those for which they are designed.
For a timer to be useful for all darkroom activities, it must accurately measure short intervals in printing exposures and longer intervals in film development. It is also helpful if the dial is large and glows in the dark. If it is to be used as a general timer, it should also have some of the best features of enlarging timers, such as electrical switching capability and repeatability.
When making enlargements, you need a timer that is extremely accurate in the range of approximately 5 seconds to 1 minute (or longer for color printing). The timer should also have the capability of turning off the enlarger at the end of the preselected timing cycle. It is also convenient to have a reset device that allows you to repeat a preset period of time. This is especially helpful when making a large number of identical exposures, such as proof-sheets. A luxury is to have the timer programmable so that it stops and starts at different intervals during its cycle, allowing you to time a variety of continuous activities without having to reset the clock for each step
It has a large dial, it glows in the dark, and it has a timing range from I second to 60 minutes. It also has a circuit to turn off the enlarger at the end of the preset cycle.
Storing chemicals is really a two-part problem. The simpler problem is where to store unmixed chemicals such as developer or fixer. An easy solution is to keep them in a storage cabinet somewhere outside of the darkroom, which will protect boxed or half-used containers from the high humidity. The more difficult problem involves storing mixed chemicals. If you are a prodigious photographer and process through developer, stop bath, fixer #1, fixer #2, hypo-clearing agent, and toning, as well as negative developers, wetting agents, and possibly color-photography chemicals, storage of mixed chemicals can be a troublesome matter. The basic rules that should be considered when planning for mixed chemical storage are:
1. The chemicals should be stored in containers that do not react with their contents.
2. The chemicals should be stored conveniently near where they are used, such as a shelf over the sink.
3. They should be accessible. If you mix in large quantities for economy or because you use a lot, it’s easier to plan on containers with spigots than it is to lift 5-gallon containers every half hour.
4. Containers should be airtight and preferably have a system to keep all air away from the surface of the chemicals. When air interacts with chemicals, it oxidizes them—an undesirable effect—so the less surface exposed to the air the longer your chemicals will last. The two best techniques for accomplishing this are containers that collapse as solution is removed, which keeps the air out, or floating lids for rigid storage containers.
5. The bottles for the chemicals should be opaque or amber colored, because light speeds the degradation of the chemicals.
Because darkroom work by its very nature produces waste products, the photographer should be aware of the nature of these products and what can be done to minimize their impact on the environment.
The factors affecting waste management are volume of effluent (the waste flowing out of the darkroom), temperature of effluent, types of chemicals used, and the ratio of chemical waste to wash water. The effluent from personal darkrooms is within most established sewer codes. The pH (measure of relative acidity or alkalinity of a liquid) is between 6.5 and 9, the temperature is less than 90°, and there are very few suspended solids. Most commercially available processing solutions contain no grease or oils, nothing flammable or explosive, and they do not have much color or odor. Photographic chemicals are generally biodegradable and will not harm municipally run biological treatment systems. It is not advisable to discharge photographic wastes directly into a septic tank and/or leach field, unless the amount is small in comparison to domestic discharge volumes or has been greatly diluted.
Many states require the installation of a back-flow prevention valve in the inlet water supply of the darkroom. The valve prevents chemicals from being sucked back into the domestic water supply if a vacuum is accidentally created in the municipal system.
The silver in the waste water is in the form of soluble silver thiosulfate from the fixing bath. It is not in the form of toxic, free-ion silver. The thiosulfate is converted by municipal processing plants into insoluble silver sulfide and some metallic silver. These are removed with other solids during clarification.
Since the earth and its resources are finite, photographic chemicals should be conserved whenever possible. The use of replenishers instead of one-shot chemistry is advised where feasible. The main darkroom chemical that is recycled is silver. It can be removed from fixing baths by several methods— metallic replacement, electrolytic recovery, and ion exchange. For larger, commercial darkrooms with high flow rates, electrolytic or ion exchange are economically reasonable. For personal darkrooms with much lower flow rates, metallic exchange makes the most sense.
Metallic exchange is a very simple process in which a more active metal than silver (usually iron) replaces the silver and goes into solution. The insoluble silver metal settles out as a solid. There are several commercially available systems on the market. Photographers can make their own by placing steel wool in a drum and pouring the fixing bath into it. The silver will form a sludge in the bottom. This sludge is sold or given to a recycling company that recovers the silver. The silver content of the sludge is hard to determine, so most companies will not pay for it. They pick it up for free and make what profit they can. Even though the photographer receives no monetary compensation, the feeling of having made an effort to help the environment is payment enough.
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