1855.] Manipulation in the Calotype process. 289 



To Excite. — I here diminish the strength of the exciting solution 

 as the heat of the weather increases. 

 The normal solutions are as follows : — 



No. 1. 



Nitrate of silver, 30 grains, 



Glacial acetic acid, 1 drachm. 



Distilled water, 1 ounce. 



No. 2. 



Gallic acid, 10 grains. 



Glacial acetic acid, | drachm. 



Distilled water, 6 ounces. 



The addition of the acetic acid enables us to keep the gallic acid 

 any length of time without decomposition. 



Take 10 minims of No. 1 and 10 minims of No. 2 mixed with 

 3 drachms of distilled water (this is just enough for a sheet 10 by 

 12 inches) pin the iodized paper face upwards on the solah board 

 as before with clear silver pins, dip a clear Buckle brush in the 

 gallo-nitrate solution, and lay on the wash as described in the iodiz- 

 ing process, lay the board on its back out of the light of the candle 

 for about a minute, then unpin the paper take it up by a couple of 

 corners, and lay it carefully, face downwards, on a dish of clean 

 filtered water, taking care not to wet the back ; agitate the dish 

 gently for a few minutes, lift up the paper, allow it to drain for a 

 few seconds and lay it on its back on a clean dry surface, blot off 

 with a fresh sheet of blotting paper, and put it, while still damp, in 

 the dark frame. "With a little management, four sheets can easily 

 be thus excited at one time. 



If the weather is warm, reduce the quantity of gallic acid to 4 

 minims. 



If the weather is hot, omit the gallic acid altogether, and a second 

 washing may be given to the paper, if it is required to keep long. 



Exposure. — It is impossible to give any safe guide in this part of 

 the process as no two lenses work alike. The shortest exposure I 

 give is 3 minutes, and I have given as much as 15 according to 

 the light. 



Development. — Here again I graduate the strength of the solu- 

 tion according to the heat of the weather, or the appearance of the 

 paper when taken out of the dark frame. 



