In regard to obtaining a greater sensitiveness, the addition of starch size in the place of the water to the albumen appears to increase it, and certainly gives great improvement in depth of the blacks. A very good way of beating up the albumen is as follows:—Take a round stick, and having cut several slits in it, from the bottom half-way up it, insert into these several pieces of quill, so that they may project on each side of the stick to the length of about half an inch or a little more, and tie up the bottom of the stick with some string wound round it to keep the quills in place. Take then the albumen, iodized as directed by Thornthwaite or any other successful manipulator, and place it in a tall cylindrical glass vessel; and taking the whisk as above prepared between the palms of the hands, roll it backwards and forwards, keeping the part armed with the quills immersed in the albumen. This is the most effective method I know, and much less tiring than the old method with the common whisk.
In answer to another Querist, I have only to reply that the black tints in the French positives are due to the presence of starch, used as a size for the paper. I have lately succeeded in producing several very beautiful and brilliant effects of this kind by passing the paper—French or English, it does not much matter which—first over a size of starch, and next (after being dried) over a combination of albumen and thin starch size, composed of equal parts of each, to which, according to the process of M. Le Gray, may be added one-fifth of a saturated solution of chloride of ammonium. This is only an improvement in the process as described by M. Le Gray, and the rest of the process will be found in his own book, or in Thornthwaite's Guide.
F. M. L.
Torquay.
Queries on Mr. Weld Taylor's Process.—I hope Mr. Weld Taylor will not withhold (from those
who would most thankfully acknowledge the favour) an amended description of his paper process, embracing replies to the following Queries:
1. How strong should the cyanide solution be that is to be added "drop by drop;" and how much of it is likely to redissolve the precipitate formed by the first mixture?
2. Should the paper be brushed with, floated on, or immersed in the solution? If either of the latter, for how long a time; and what then?
3. How is the bath of nitrate of silver prepared, and the mode of applying it to the paper?
4. How much sulphuric acid is added to a given quantity of water, in which the paper is placed after removal from the exciting bath; and is it immersed or floated?