Darkrooms

The major disadvantage of conventional film is that it is light sensitive, and cassettes must be loaded and unloaded in a light-tight place. We describe the use of both informal and formal darkrooms, as well as portable darkroom construction at the field site.

An informal darkroom or film-changing space can be created in a very short time at the location of the imaging study. A room, such as a bathroom or even a closet, can often be easily rendered light tight (Figure 2.14). Black gardening plastic or black pool liner held

Figure 2.12A Positioning for a lateral projection of the skull of a mummy in urbania, Italy. the nonscreen film holder (a) was held in place by the tape. the x-ray tube (B) was placed on a pile of boxes for the exposure.
Figure 2.12B the resulting Polaroid image of the standing mummy in urbania, Italy. Note the extreme wear on the maxillary molar (arrow).

in place by duct tape will eliminate light from windows and around doors with particular attention given to door jambs (Figure 2.15). More inventive light-tight film changing spaces were created within museum displays, a circular staircase leading from a museum up into a cemetery, bathroom stalls, and a church confessional (Figure 2.16).

Exposed films can be stored in a light-tight transfer case (BarRay®) that resembles a briefcase. These containers can easily hold about 100 exposed films and can be transported to an automatic processor in a formal darkroom.

Formal darkrooms may be located at medical facilities, universities, and chiropractic, podiatric, and veterinary practices. Many of these facilities have automatic film processors within their darkrooms. Since processing images of remains will not have precedence over patient or client images, using established automatic, or even manual processing facilities,

Figure 2.13 cold packs taped the either side of the x-ray tube to cool the unit during multiple exposures.

Figure 2.14 An example of a "native hut" in a museum in Iquique, Chile, that was turned into a darkroom to load and unload cassettes. In order to make the space light tight, the inside of the window (arrow) of the hut was covered with black plastic and a door was fashioned with black felt. Incidentally, the felt, acquired from a local fabric shop, had a Christmas tree and star pattern that was fluorescent. However, the wavelength of the light given off by the fabric did not fog the x-ray film.

Figure 2.14 An example of a "native hut" in a museum in Iquique, Chile, that was turned into a darkroom to load and unload cassettes. In order to make the space light tight, the inside of the window (arrow) of the hut was covered with black plastic and a door was fashioned with black felt. Incidentally, the felt, acquired from a local fabric shop, had a Christmas tree and star pattern that was fluorescent. However, the wavelength of the light given off by the fabric did not fog the x-ray film.

Figure 2.15 Black plastic used to cover the window in a bathroom.
Figure 2.16 Material (arrow) placed over the door of a confessional in a church in Moquegua, Peru, to convert it into a light-tight film changing "room."

must be scheduled for a specific time of day. Depending on the volume of films processed per day, the quality of the developing chemistry can change during a particular day or after a certain number of films has been processed. Therefore, large numbers of films processed at once, commonly termed batch processing, can be problematic. First, test exposures should be taken bracketing the exposure setting, meaning that an exposure should be made with what would be the expected mAs. Next, a second exposure is taken with half the mAs and then a third exposure with double the mAs. All three images are processed at the time of day that the batch processing would take place. From the processed images, the best exposure setting is noted, and that becomes the mAs that will be used in the field imaging project.

Usually, the processing facility is a minimum of several miles or kilometers from where the study is taking place, and trips to process the films can be very time consuming. Even if the technical factors result in an acceptable image, a film may need to be repeated due to poor positioning or an inadequate demonstration of a particular anatomical or pathological feature. Repeat imaging drastically slows down the progress of the study and may severely limit the number of specimens examined.

If there is no place to create an informal darkroom, and no formal darkroom is available, a portable darkroom can be constructed. Although there are commercially available portable darkrooms, they are typically designed for standard photography and are too small for the needs of x-ray film processing. A portable darkroom can be constructed using pre-cut PVC pipe with the appropriate connectors as the framework (Figure 2.17). An 8 x 3 ft (2.4 x 0.9 m) length of black felt is first draped over the front to act as the first layer of the

Figure 2.17 The PVC pipe frame for the portable darkroom.

door (Figure 2.18). A second layer of black felt is laid over the first layer to create a double door to ensure a light-tight opening. The entire frame is then covered with light-tight material and secured in place with clamps (Figure 2.19). If it is designed well, there is room for extra film and the three necessary processing tanks. The authors have used this darkroom

Figure 2.18 Two layers of felt are used to create a light-trap door.

Figure 2.19 The entire PVC pipe frame covered with two layers of black plastic at right angles to each other.

successfully on such remote locations as on a rooftop and adjacent to a Buddhist temple. If you really want to get fancy, an entry fly can be affixed to the door end to provide shade (Figure 2.20).

Film processing, too, must be considered. If only eight to ten 14 x 17 in. (35.5 x 43 cm) films are going to be processed per day, three large plastic photographic trays would suffice for the chemistry. If more than ten films per day are going to be processed, a conventional manual x-ray film processing workspace must be constructed. The easiest method would

Figure 2.20 The portable darkroom was covered with a surface and a tent fly to shield the entrance.

"space blanket"

to provide a reflective be to acquire a stainless steel tank system designed for this purpose. Until recently, small chiropractic, podiatric, and veterinary practices manually processed their x-rays. Once they converted to automatic processing, their used wet processing tanks were discarded. These units may be available from local radiographic equipment dealers. Generally, these units consist of two 5-gal tanks, one for developer and the other for fixer, that sit within a much larger, approximately 20-gal tank that would be filled with water. The water tank served several purposes. It was used to wash the film after development and fixing, and it also maintained the temperature of the chemistry. The large tank usually was directly connected to the water supply so that a continuous flow would eliminate contaminated water and also wash the fixer from the film before it went to the dryer.

Since the water/wash tank is so large, it is not practical to transport to a field facility, particularly if it is outside the continental United States. A more appropriate approach would be to acquire three 5-gal stainless steel tanks, one each for developer, fixer, and water. The latter would only be used as a wash between the developer and fixer. As a cautionary note, many of the 5-gal tanks have a cork located on the bottom of the tank to permit drainage. When submerged in the larger tank, the cork does not present a problem. However, if the tanks are used independently, they must be placed on a rack with thickness equal to the thickness of the cork or they will be unstable.

Another option is to construct three tanks out of marine plywood. The wooden containers are nearly indestructible and would also serve as sturdy transport boxes to bring material to the site. To transform the plywood boxes into watertight tanks, the authors fabricated a liner from heat-sealed vinyl roofing material (Figures 2.21A and 2.21B). A fiberglass liner would also serve the same purpose. The three processing tanks need to have lids to avoid evaporation, which would cause a change in the chemical concentrations. It is important to place the tanks in order of use in the developing process and to secure the tanks to avoid knocking them over in the dark (Figure 2.22).

Figure 2.21A Vinyl roofing material heat-sealed to create a liner for plywood tanks.
Figure 2.21B The vinyl liners within plywood processing tanks. A PVC pipe (arrow) was placed on the faucet to permit better flow into the wash tank.

A final wash tank would have to be devised on site. The easiest approach would be to use a 30-gal plastic container with a hose to provide continuous water flow (Figure 2.23). If an electrical power supply is available, a circulating water pump can be placed into the container to move the water within the tank.

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