DARKROOMS AND DARKROOM PRACTICE 



Table I. — Safe Lights 



567 



of wax, or given several coats of corrosion-resistant paint, each coat being dried thor- 

 oughly before the next one is applied. 



Enameled trays will chip if dropped on a hard surface; glass and hard rubber trays 

 will break if similarly dropped. On the other hand, acid does not attack hard rubber 

 or glass trays while it will attack enameled metal traj's if a slight break in the surface 

 material occurs. Enamel will be stained by certain developing solutions or by dyes 

 used in mordanting prints. These stains may be removed, however (see page 568 

 for tray-cleaning solutions). 



When any appreciable number of films or plates are to be processed, tanks of the 

 appropriate size are usually employed. These may be made of metal or nonmetallic 

 materials. Slots are placed along the side into which the plates slide, or the materials 

 are placed in hangers which are large enough not to slip into the solution when laid 

 across the top of the tank. In the average laboratory it is probable that solutions 

 kept in tanks will be allowed to become exhausted more often than if tray processing 

 is done, because of the bother of cleaning the tanks and mixing up new solutions. 



Obviously the size of trays or tanks will depend upon the size of materials to be 

 processed. Two sizes of tray will suffice for general amateur work, a set of small ones 

 for negatives, up to 5 by 7 in. and a set of large trays for 11- by 14-in. prints. A tray 

 for an 11- by 14-in. print must have an inside dimension that is larger than 11 by 14 

 if it is to be used successfully. The following table will indicate the dimensions that 

 have been found useful for making prints of various sizes. 



Table II. — Print and Tray Sizes ^ 



Tanks for use with miniature films (35 mm., etc.) differ in construction, naturally, 

 from flat tanks used for cut films or plates. They are of two general types. In one 

 the film is threaded into slots in a composition (hard rubber, bakelite, etc.) molded 

 form. This operation must be done in the darkroom. The reel is then placed in the 

 tank, a lighttight lid is affixed after which the tank may be taken out into ordinary 

 daylight. In the other type the film is placed on an "apron" made of celluloid, soft 

 rubber, or other material which fits into the tank. A metal tank will change tem- 

 perature in accordance with the ambient, so that greater care must be exercised in 

 maintaining its temperature while processing is taking place. The bakelite tanks do 

 not transmit temperature changes so easily, and, if the solution is placed in the tank 



