134 THE A B C OF PHOTO - MICROGRAPHY 



these imperfections are now almost unknown, 

 there are still some makes of plates, the films 

 of which are so soft as to chip or rub off in 

 patches all around their edges, even under 

 the most careful handling, giving them a 

 most unsightly appearance to say the least, 

 and often spoiling a subject which nearly 

 covers the plate. Several remedies are sug- 

 gested. If the negative is transferred directly 

 from the developer to a fairly strong chrome- 

 alum bath, in which it should be left several 

 minutes, the film will usually be sufficiently 

 hardened to prevent any rubbing off at the 

 edges. But mark carefully, the plate must be 

 thoroughly washed previous to being placed in 

 the fixing bath, in order to remove the alum 

 which greatly retards action of the hypo. It 

 must not be forgotten that complete fixation 

 and removal of the last trace of hypo are 

 essential to the permanence of a negative. 

 Therefore, the washing after treatment with 

 alum must not only be very thorough, but 

 the negative should be allowed to remain in 

 the fixing bath for a considerable time after 

 the white has entirely disappeared from its 

 back, and the final washing cannot well be 

 too prolonged or complete. I desire to urge 

 this most earnestly upon all my readers who 



