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



suspended in the air, and, in the absence of a better expedient, 

 it may be pinned across a string by one of its corners. When 

 dry it may be smoothed by pressure. It is now " iodized " 

 and ready for use, and in this state it will keep for any length 

 of time if protected from the light. The second process is 

 that of exciting, or 



20. Preparing the Paper for the Camera. — For this purpose 

 are required the two solutions described by Mr. Talbot, namely 

 a saturated solution of crystallized gallic acid in cold distilled 

 water, and a solution of the nitrate of silver of the strength of 

 fifty grains to the ounce of distilled water, to which is added 

 one-sixth part of its volume of glacial acetic acid. For many 

 purposes these solutions are unnecessarily strong, and unless 

 skilfully handled they are apt to stain or embrown the paper ; 

 where extreme sensitiveness therefore is not required, they 

 may with advantage be diluted to half the strength, in which 

 state they are more manageable and nearly as effective. The 

 gallic acid solution will not keep for more than a few days, and 

 only a small quantity therefore should be prepared at a time. 

 When these solutions are about to be applied to the iodized 

 paper, they are to be mixed together, in equal volumes, by 

 means of a graduated drachm tube. This mixture is called 

 " the gallo-nitrate of silver." As it speedily changes and will 

 not keep for more than a few minutes, it must be used without 

 delay, and it ought not to be prepared until the operator is 

 quite ready to apply it. 



21. The application of this "gallo-nitrate" to the paper is 

 a matter of some nicety. I doubt if it be possible to apply it 

 successfully with brushes: and it appears to me, that one ap- 

 plication of the gallo-nitrate as completely unfits a brush for 

 a second, as the dipping of a sheet of paper in ink would unfit 

 it for writing upon. It will be found an improvement to apply 

 it in the following manner: — Pour out the solution upon a 

 clean slab of plate glass, diffusing it over the surface to a size 

 corresponding to that of the paper. Holding the paper by a 

 narrow upturned margin, the sensitive side is to be applied to 

 the liquid upon the slab, and brought in contact with it by 

 passing the fingers gently over the back of the paper, which 

 must not be touched with the solution. 



22. It has been recommended at this stage, "to let the 

 paper rest for half a minute, and then to dip it into water and 

 dry it with blotting-paper," which I apprehend has been the 

 fruitful cause of much failure and disappointment, by the 

 staining and embrowning of the paper, and by the partial re- 

 moval of its sensitive surface. 



23. As soon as the paper is 'wetted with the gallo-nitrate, it 



