Mr. Cundell on the practice of the Calotype Process. 327 



fifty grains of common salt. He found that the chlorinated 

 iodide of silver is infinitely more sensitive than the simple 

 iodide ; and by this addition of common salt, a similar, though 

 a less remarkable, modification is obtained of the sensitive 

 compound. Pour the solution into a shallow flat- bottomed 

 dish, sufficiently large to admit the paper, and let the bottom 

 of the vessel be covered to the depth of an eighth of an inch. 

 The prepared side of the paper having been previously marked, 

 is to be brought in contact with the surface of the solution, 

 and, as it is desirable to keep the other side clean and dry, it 

 will be found convenient, before putting it in the iodine, to 

 fold upwards a narrow margin along the two opposite edges. 

 Holding by the upturned margin, the paper is to be gently 

 drawn along the surface of the liquid until its lower face be 

 thoroughly wetted on every part ; it will become plastic, and in 

 that state may be suffered to repose for a few moments in con- 

 tact with the liquid ; it ought not however to be exposed in 

 the iodine dish for more than a minute altogether, as the 

 new compound, just formed upon the paper, upon further ex- 

 posure would gradually be redissolved. The paper is there- 

 fore to be removed, and, after dripping, it maybe placed upon 

 any clean surface with the wet side uppermost until about half 

 dry, by which time the iodine solution will have thoroughly pe- 

 netrated the paper and have found out and saturated every par- 

 ticle of the silver, which it is quite indispensable it should do, 

 as the smallest portion of undecomposed nitrate of silver would 

 become a black stain in a subsequent part of the process. 



18. The paper is now covered with a coating of the iodide 

 of silver; but it is also covered, and indeed saturated, with salt- 

 petre and with the iodide of potassium, both of which it is in- 

 dispensable should be completely removed. To effect the 

 removal of these salts, it is by no means sufficient "to dip the 

 paper in water;" neither is it a good plan to wash the paper 

 with any considerable motion ; as the iodide of silver, having 

 but little adhesion to it, is apt to be washed off*. But the mar- 

 gin of the paper being still upturned, and the unprepared 

 side of it kept dry, it will be found that, by setting it afloat on 

 a dish of clean water, and allowing it to remain for five or ten 

 minutes, drawing it gently now and then along the surface to 

 assist in removing the soluble salts, these will separate by their 

 own gravity, and (the iodide of silver being insoluble in water) 

 nothing will remain upon the paper but a beautifully perfect 

 coating of the kind required. 



19. The paper is now to be dried; but while wet, do not 

 on any account touch or disturb the prepared surface with 

 " blotting-paper," or with anything else. Let it merely be 



