534 HANDBOOK OF PHOTOGRAPHY 



3. Prevention. — For drying negatives quickly using alcohol bath, the alcohol 

 should be diluted slightly with water. Ten parts of alcohol to one part of water 

 is approximatelj^ correct. The temperature of the drying air should not exceed 95°F. 



4. Remedy. — The white opalescence may be removed by soaking the film in water 

 and redrying slowly. 



Stains and Discolorations 

 Aluminum Sulphite Stains. 



1. Distinguishing Characteristic. — White powdery stains on negative. 



2. Cause. — Aluminum sulphite stains caused by an insufficiently acid fixing bath 

 as a result of using an exhausted or incorrectly compounded fixing bath. When 

 sodium sulphite, as from the developer, is added to a fixing bath containing alum, the 

 acid fixing bath is neutralized, and ultimately a white precipitate of aluminum sulphite 

 is formed which turns the bath milky white and settles as a white sludge. 



3. Prevention. — Avoid a developer containing excessive alkali. Between develop- 

 ment and fixing, the negative may be washed in clear water or in an acid stop bath. If 

 an acid stop bath is used, care must be taken to see that the acid carried over into 

 the fixing bath is not sufficient to cause sulphurization of the fixing solution. 



4. Remedy. — Aluminum sulphite stains may be removed by hardening the negative 

 in an alkaline formalin solution. The negative should then be washed for several 

 minutes in a 5 per cent solution of sodium carbonate, after which the negative should 

 be washed thoroughly in clear water. 



Blue-green Stain. 



1. Distinguishing Characteristic. — Blue-green stain after fixing. 



2. Cause. — Frequently caused by using chrome-alum fixing bath at elevated 

 temperatures. 



3. Prevention. — Maintaining fixing bath at temperatures not exceeding 70°F. 



4. Remedy. — None. 



Blue Stains. 



1. Distinguishing Characteristic. — Blue stains covering part or all of negative. 



2. Cause. — Usually due to presence of iron in the processing solutions, but is some- 

 times due to the presence of amidol. 



3. Prevention. — In making up solutions, use iron-free water. 



4. Remedy. — If stains are due to iron, they may be removed as indicated under 

 Developer Stains, page 535. If due to Amidol, they may be removed by immersing 

 the negative in a 10 per cent solution of sodium bicarbonate, washing, and drying. 



Brown Areas. 



1. Distinguishing Characteristic. — Brown areas on negative often occurring as 

 scum deposit on the surface. 



2. Cause. — Probably from scum of oxidized developer or deposits of silver sulphide 

 in the developing or fixing baths. 



3. Prevention. — Use of fresh and properly compounded processing solutions. 



4. Remedy. — (See under Developer Stains, page 535.) 



Colored Areas. — (See Dye Stains, page 535.) 

 Colored Negatives. 



1. Distinguishing Characteristic. — General, over-all stain on negative, usually 

 yellow, brown, or sepia. 



