132 PRACTICAL PHOTO-MICROGRAPHY. 



about 160 degrees in an enamelled flat iron dish, a Bunsen or 

 other burner serving to keep the temperature up while a suc- 

 cession of prints are developed. On this hot solution made 

 alkaline the print is laid for a few seconds ; the previously 

 pale image will almost instantly flash into a black picture, the 

 high lights remaining for the time yellow. If the printing 

 or exposure has been too short the developing solution should 

 be hotter, say 180 degs., if the exposure was too long the 

 bath should be more cool, say 110 degs. It will generally 

 be found best to expose to such an extent that the develop- 

 ment will be correct at 160 degs. We usually have slightly 

 acidified the bath with oxalic acid and got fine results, but 

 the Company now recommend that the bath be kept faintly 

 alkaline. 



After development, which, conducted as above, will not oc- 

 cupy more than 15 or 20 seconds even with a "cool" solution 

 such as suggested, the print is to be put straight into : 



Water 60 parts. 



Hydrochloric Acid, 1 " 



Two more baths of the same ingredients are to follow, and 

 the third bath must never show any yellow tinge ; if it does 

 show such a tinge it must be followed by a fourth bath. When 

 No. 1 bath becomes very yellow it should be rejected and the 

 others be advanced each a step, No. 2 becoming 'No. 1, etc. 

 After the baths the prints are to be washed for about 15 

 minutes in running water to remove the acid ; they are then 

 finished. 



Pizzighelli's paper requires no development, but at time of 

 printing it must be slightly damp, not wet. To damp it we 

 may breathe on it or put it into a box in company with pieces 

 of wet blotting paper. Printing may be partly performed by 

 light, and finished with cold solution : 



Saturated Solution Sodic Carbonate, 5 parts. 



Distilled Water, 100 " 



Clearing is performed as above. 



The latest process put forward by the Platinotype Company 

 is convenient and good. The company send out with the paper 



