86 



THE AMERICAN MONTHLY 



[May, 



gives exaggerated contrasts. Never- 

 theless, the novice is frequently 

 puzzled to decide whether a plate is 

 over-exposed or under-exposed, when 

 it is evident that something is wrong 

 about it. In this case, as in all others, 

 an understanding of their peculiar 

 effects will be of some assistance. 



In the case of an over-exposed plate, 

 the light has acted so long that the 

 parts of the plate which should be 

 unchanged have been affected, while 

 in the high-lights the silver salt is so 

 changed that it is impossible to obtain 

 intensity by development. Over- 

 exposure is not so noticeable when 

 a plate is developed with the ferrous 

 oxalate developer, as when an alkaline 

 pyrogallic developer is used. ' 



In an under-exposed plate the 

 strong contrasts are due to the insuffi- 

 cient light from the shadows, so that 

 while the strong lights are black, all 

 the dark parts of the object are white 

 in the negative without the gradations 

 that they should have. 



To a certain extent the operator 

 can control the development of the 

 plate, and remedy the defects of in- 

 correct exposure. This is done either 

 by changing the strength of the de- 

 veloper, or by the addition of chemi- 

 cals to counteract the effect of the 

 light. Such chemicals are designated 

 restrainers. We now pass to the 

 practical operation of development. 



From among the numerous devel- 

 opers in use we will only give those 

 which we have used and found satis- 

 factory. 



Looking through the photographic 

 literature of the day it would seem 

 that a large proportion of those' who 

 are engaged in photographic work, 

 either as amateurs or professionally, 

 deem it a bounden duty to get up 

 new developers, which, in most cases, 

 are merely modifications of old and 

 well known formulas. We have done the 

 same thing with the pyrogallic acid 

 developer, but not with any intention 

 of improving the formula for work. 

 Our object has been to obtain concen- 

 trated stock solutions which will keep 



for any length of time, from which 

 the working solutions can be made 

 by dilution. Mr. J. T. Taylor has 

 also published a formula for a concen- 

 trated developer in the Photog'^aphic 

 Times ^ which is virtually the same 

 although not so strong as our own. 



The solutions we have used are the 

 following : — 



A. Concentrated Pyrogallic Acid 

 Developer. 



Pyrogallic acid, 120 grains. 



Oxalic acid, 60 grains. 



Water, 2 ounces. 



Half a drachm of this solution con- 

 tains nearly 4 grains of pyrogallic 

 acid. 



B. Saturated solution of Washing- 

 soda, 



C. For a restrainer we use ammo- 

 nium bromide (or potassium bromide) 

 50 grains ; water i ounce. 



To prepare a solution for develop- 

 ing a plate, take half an ounce of B. 

 and add to it two ounces of water. 

 Then take half a drachm of A. and 

 add it to two ounces of water. Mix 

 equal parts of these two solutions 

 and use immediately. In practice we 

 have two bottles for holding the 

 diluted solutions, and we make up 

 about live ounces of each at one time, 

 as they will keep perfectly well. We 

 develop in developing dishes that 

 will take a 5 x8 plate, and when using 

 4x5 or smaller plates it is frequently 

 possible to develop two of them 

 together. Such a pan requires about 

 an ounce of each solution for each 

 operation. The solution thus prepared 

 is the same as that lately introduced 

 by Mr. J. H. Newton, and already 

 favorably known. 



There is another developer very 

 extensively used in this country known 

 as the ferrous oxalate developer. A 

 good ferrous oxalate developer may 

 be prepared in this way : — 



I. Potassic oxalate, neutral, 8 oz. 

 Potassium bromide, 25 gr. 



Water, 32 oz. 



Acidify with citric or oxalic acid, until 

 it turns blue litmus paper red. 



