PHOTOGRAPHIC PROCESSES. 89 



DESCRIPTION OF LEVELLING SLAB. 



Screw in top of table or shelf three screweyes for 

 each plate ; level plates by means of spirit level. In 

 very hot days or climates it may be necessary to have 

 underneath the shelf a zinc-lined drawer in which ice 

 can be placed ; in this case the shelf above the drawer 

 should be lattice work. 



There is another way of working this formula 

 which some might prefer. I do not. But as good 

 results can be obtained as by the other, I will give it. 



Take the silvered gelatine, heat it to 150, add the 

 alcohol, albumen, and chrome alum, and let set as 

 before described, but not get dry. Make a bath as 

 follows : 



Ammonium bromide, 720 grains. 

 Soda carbonate, 160 grains. 

 Alcohol, 4 ounces. 

 Water, 12 ounces. 



The alcohol in this formula is not absolutely 

 necessary; but when all water is used it takes longer 

 to get the bromide of silver to form. If you do not 

 use the alcohol employ water instead, and leave plates 

 in brine longer. 



Put this bath into a grooved box the size of plates 

 you wish to make, put the silvered plates in the 

 bromide of ammonium bath and let set 24 hours, 

 take them out, put into another grooved box and 

 wash, put them on rack to dry, and they are ready 

 to use ; or they can be used wet but they will be 

 slower. 



