WITH THE -MICROSCOPE. 2/1 



weak mucilage or gum water. In this case care must be taken to 

 well dry the plate prior to varnishing, as gum is to a small extent 

 an absorbent of moisture. 



In the journals and manuals on general photography various 

 methods are set forth to endeavour to procure by one operation 

 sufficient intensity to print from. Mr. M. Carey Lea strongly recom- 

 mends gelatine soaked, the water poured off, then acted on (without 

 heat in all the operations) by sulphuric acid, the acid to be taken up 

 by the gradual addition, when cool, of clean iron filings or thin iron 

 wire, and the excess of acid finally removed by the acetate of soda. 

 Others have proposed the solution of gelatine in acetic acid or 

 nitric acid and the addition of this, from a few drops upwards, to 

 the ordinary protosulphate of iron or ammonio sulphate of iron 

 developer, without the acetic acid (Dr. Towler's method). Some 

 use honey or a little albumen added to the pyro-acetic and silver 

 solution for the same object. 



34G. Varnishing the Plate. When the plates are dry, clean off 

 the edges with a damp cloth held on the forefinger nail, wipe well 

 the back, and hold the plate before a clear fire until moderately 

 warm to the back of the hand ; take it by one corner and pour on 

 the varnish (Soehnee is very good). Allow it to flow freely over the 

 surface and remain for half a minute or less on it, then pour back 

 the surplus into the bottle from one corner, not rocking the plate ; 

 let it drain a little, then hold the plate towards the fire vertically, 

 the edges from which the varnish was poured being downwards, and 

 wipe them with a piece of rag or tissue paper to prevent a thickened 

 line being formed and extending inwards as the plate dries. If 

 intended for enlarging, it is far better not to varnish the plate in 

 any way ; but to prevent the surface from being injured, it may be 

 flowed with weak albumen, then dried, and plunged into a dish of 

 alcohol as advised by some. 



347. Of Cleansing Old Plates. The soiled and used plates can 

 be cleaned by the fresh use of washing soda ; those varnished should 

 be allowed to soak in a very hot strong solution of this substance, 

 or rubbed with a pledget of tow dipped in nitric acid ; or treated 

 by Mr. M. Carey Lea's method. If they are to be used again 

 they must be cleaned with great care. 



The third stage in the manipulation closes with the production 

 of the image on paper, technically called Printing. 



PRINTING. 



The negative, if it be preferred, can be handed to a professional 

 photographic printer, who, however, should be acquainted with the 



