The international photographer (Jan-Dec 1934)

Eight The INTERNATIONAL PHOTOGRAPHE R February, 1934 A Temperature Controlled Portable Laboratory By Paul R. Harmer PTACHED hereto are the original drawings for a temperature controlled portable labora4| tory which was designed primarily for use in the tropics, but I have altered my previous plans and it is now adaptable to any climate in the world and is little affected by room or outside temperature. Its only requirement is a small flow of running water and enough electricity to operate the motor on the ice machine. Figures 1, 2 and 3 show the plan or layout of the tanks ; figures 4, 5 and 6 are elevations of the same ; the other drawings are details and accessories. With everything in readiness the estimated time for the following is : Time 2000 ft. negative, 200 ft. per 10 minutes 1 hr. 40 min. 2000 ft. sound track, 200 ft. per 5 minutes 50 min. 4000 ft. positive, 200 ft. per 5 minutes 1 hr. 40 min. Total time -------------- 3 hr. 10 min. Working an eight or twelve hour day, the capacity of the equipment is quite all right for most companies, even to getting out dailies, so the picture can be rough cut before returning to the studio, thereby giving satisfaction for all concerned. An experienced operator should be able to turn out film which would compare in quality with that of any commercial laboratory. The essential parts of the equipment are as follows: General Electric Condensing Unit (ice machine) model CM-6-W equipped with a one-horsepower motor and water cooled coils. This insures a temperature drop of 20 degrees in the tap water ; for instance, if the available water is 85 degrees at the tap, the machine is capable of delivering 60 gallons of water an hour at 65 degrees and the water cooled coil is the sure way to keep the condenser cool. The next item is the heating element which is necessary at times and is capable of raising the water temperature 20 degrees — from 45 to 65, which will take care of most conditions. This is a General Electric Calrod No. 133-W53, 3000 watts. Both of these are connected to and controlled by a thermostat placed in the flow inside the regulator tank. Two satisfactory thermostats have been tried : the Bristol Model 177 and the Mercoid, with a 50-80 degree range, with a special helical bulb. This instrument is set to a plus or minus of one-half of one degree. Its control is so sensitive and accurate that a three-day test proved the total variation in the center of the developer was two-tenths of one degree. This thermostat and its relay operate through a double throw, three-pole switch which reverses the thermostat and all you have to do is turn on the electricity and let it take care of the temperature. The principle of keeping the solutions at a constant temperature is one of transmission. The Monel metal developei tank and Monel metal hypo tank are surrounded on the sides and the bottom by running water at 65 degrees Fahrenheit. Good insulation from outside temperature is obtained by using tanks made of 1^ incn Oregon pine and insulated by two inches of cork board, waterproofed for this purpose. Hinged lids are useful to assist in reducing loss of temperature, but most operators would find them in the way and unless the room temperature was interfering with the operation they could be dispensed with. Beginning at the tap, we will follow the water through the laboratory. The first place it comes to is the weir box, with its float, which regulates the flow of water. Figures 1, 4 and 9 illustrate the location and purpose; a one-eighth inch slot in the weir and 1.91 of an inch high will flow exactly 60 gallons an hour, by gravity ; the principle of the float is to maintain this height and thus eliminate adjustments, due to variable pressure in the water main. The water then flows through the temperature regulator and into the square tank surrounding the developer. It flows diagonally across to a pipe which carries it to the square tank surrounding the hypo. It again flows diagonally to the other side where it enters another pipe which carries it to the far corner of the clean wash. Here it starts back. When it leaves this tank it enters its first underfeed-overflow pipe, as illustrated in Figure 10; the chemicals, being heavier than the water, settle to the lower part of the tank and the underfeed draws them off as fast they accumulate. Next, the water flows to the rough wash, then through another underfeed-overflow pipe to the rinse tank, which is another square tank made of Monel metal and resting on a grid, to allow its chilling effect to the compartment below. The water circulates across this tank and into the outlet to the accessories which we will take up later. Figure 1 1 shows how a Monel metal pipe is flanged to the wooden tank, then the threaded nipple on the round Monel tank is screwed down into this pipe, thereby making it possible to get a water-tight connection and still have it so the tank can be removed if required. A rubber stopper can be used instead of the gate valve illustrated if desired. One thing should be mentioned regarding these Monel tanks: They should be made of 16 gauge Monel plate, with welded seams, for a first class job, also an apron should be fitted around the sides of the top, in order that the water is not polluted by slopping developer or hypo into the circulating system. Wooden lugs laid in the direction of the flowing water keep the Monel tanks and film racks from resting on the bottom, also allowing the chemical to settle to the bottom of the wash tanks and be quickly carried away. The developer tank and the hypo tank are 24 inches in diameter and 15 inches deep, with a maximum capacity of 29 gallons ; the rinse and wash tanks are 24 inches by 24 inches by five inches deep, but as the water level is maintained two inches down this gives them the capacity of five gallons each, which maintains a complete change of water every five minutes in each tank. We are now ready to consider the type of film developing reel or rack. Stineman's developing reel, 200 foot length, is satisfactory and when one becomes ac Please mention The International Photographer when corresponding with advertisers.