DARKROOMS AND DARKROOM PRACTICE 569 



portion of the sink is filled with water at some desired temperature, while the weir 

 blocks off the remainder of the sink (the portion containing the drain) the tray of 

 solution may be floated in the larger body of water while the drain is available for 

 waste disposal. 



Stone or earthenware sinks should be covered with a material which is softer than 

 the sink itself so that beakers or other glassware dropped on it will not break. Rubber 

 mats, floor mats, or door mats may be used; linoleum or asbestos is satisfactory. 



Thermometers, and Weighing Scales. — Metric system weights are to be preferred, 

 although avoirdupois weights are satisfactory. Most formulas are now written in 

 both systems. In a small studio a maximum weight of SM oz. (100 g.) will probably 

 be encountered and so the smallest studio scales may be employed. Scales for larger 

 laboratories must, naturally, weigh greater quantities of material. Scales capable of 

 measuring up to 25 lb. may be placed upon a shelf or table; scales for greater quantities 

 exist in the form of platform scales. 



The pans of a laboratory scales should not be permitted to touch any of the chem- 

 icals; a piece of paper should be placed upon the weighing pan and counterbalanced by 

 a similar piece on the other pan. If the scales are kept in a damp darkroom, the 

 wooden base may swell, the metal parts tarnish or become covered with verdigris, and 

 the bearings may become so dirty that accurate weighing is difficult. This is another 

 reason why the weighing of chemicals and the compounding of formulas should not 

 be done in the processing room itself. 



It does not matter much whether thermometers are calibrated in Fahrenheit or 

 centigrade. Probably most American and English workers are more familiar with 

 Fahrenheit and have a better idea of the variation caused by 1° difference in tempera- 

 ture in this system than centigrade. Metal thermometers have a bad habit of tarnish- 

 ing so that the calibration is hard to see; they also peel off in thin layers of oxide. 

 Glass thermometers which are also used as stirring rods frequently lose the paint in 

 which the calibrations are marked, making it most difficult to read the temperature 

 scale in the semilight of the darkroom. 



The Weston type of thermometer consisting of a long thin metal rod with a dial- 

 type indicator at the top does not seem to corrode; the action is remarkably fast, and 

 the dial is easy to read. It is inclined to be top heavy, however, and, when placed in 

 a tray which is rocked or tilted, has a tendency to roll around and get in the way or to 

 roll out and break. The "crystal" glass cover over the dial is heavy but it will break. 



Darkroom Practice. Flow of Work. — If the darkroom is properlj^ arranged, work 

 done there will flow easily from one stage to another. For example, sensitive paper 

 should not have to be moved over a tray of developer to be placed in a printer or under 

 an enlarger. In a photofinishing establishment this even and easy flow of work is very 

 important so that operators do not get in each other's way. Operations which may be 

 carried out in full illumination should be excluded from the processing laboratory if 

 possible, so that full advantage of better working conditions (better visibility etc.) 

 can be utilized. 



If the photographer works out a standardized method of procedure, he will find that 

 he will have less waste and that his work will be less tiring. Thus developing, rinsing, 

 fixing, washing may proceed from left to right (or vice versa), and this should be 

 standardized no matter whether it is films that are being developed in absolute dark- 

 ness or whether prints are being processed under appreciable illumination. 



Maintenance of Temperature. — If the darkroom is warmer or cooler than the desired 

 solution temperature, the photographer must take steps to overcome the progressive 

 change in solution temperature. The simplest method is to float a tray containing 

 the solution in a larger tray filled with water of the required temperature. By means 

 of a mixing faucet in which cold and hot water may be brought to the desired tem- 



