Blanquart Everard, Sagnez, and some others, have recommended that in the preparation of the highly sensitive photographic papers no brushes should be employed. They pursue the following plan : the solutions are poured upon a perfectly flat piece of glass, and the paper carefully drawn over it, and, if necessary, pressed closer by another plate of glass.

A plan of iodizing paper has been proposed by, Mr. Jordan, which offers many advantages. Iodide of silver is precipitated from the solution of the nitrate by iodide of potassium, and this precipitate being lightly washed, is redissolved in a strong solution of the latter salt. This solution is applied to the paper, and the paper allowed to dry ; after this it is placed face downwards upon some clean water ; the iodide of potassium is removed by this, and a pure iodide of silver left on the paper.

If the paper carefully and properly iodized is washed with a very dilute solution of the aceto-nitrate of silver, that is to say, with a solution composed of 10 grains of nitrate of silver to 1 fluid ounce of distilled water, and 10 drops of a concentrated solution of gallic acid be added to another ounce of distilled water and the two mixed, it will keep for three weeks or a month. It may be used dry in the camera, and afterwards developed with the gallo-nitrate in the usual manner. It will, however, require an exposure in the camera of from ten to twenty minutes, and is, therefore, only useful for still objects; but for buildings, landscapes, foliage, and the like, nothing can be more beautiful.

Le Gray recommends as a highly sensitive paper for portraits the following :—

Distilled water..... 6200 grains.

Iodide of potassium . . . 300 „

Cyanide of potassium ... 30 „

Fluoride of potassium ... 1 „

Papers are washed with this, and then with his strong solution of aceto-nitrate of silver, which is described in the section devoted to the wax paper process.

M. A. Martin, who is aided by the Imperial Academy of Sciences of Vienna in his endeavours to improve the photographic processes, and render them available to the purposes of art, has published the following as the best proportions in which the solutions should be made, and the order of their application.

For the negative picture:

First

Iodide of potassium.....1/2 oz.

Distilled water......10 fluid oz.

Concentrated solution of cyanide of potassium.....7 drops.

Second

Nitrate of silver ...... 7 drachms.

Distilled water......10 fluid oz.

Strong acetic acid.....2 drachms.

Third

A concentrated solution of gallic acid.

Fourth

Good spirits of wine.

Fifth

Hyposulphite of soda . . . . 1 oz.

Distilled water......10 fluid oz.

For the positive pictures:

First

Chloride of sodium . . . . 168 grains.

Distilled water..... 10 oz.

Second

Nitrate of silver . . . . 1 oz.

Distilled water..... 10 oz.

Third

Hyposulphite of soda .... 1 oz.

Distilled water..... 40 oz.

Nitrate of silver 30 grains, dissolved in 1/2 oz. of distilled water, to be poured into the solution, in a small stream, while it is constantly stirred with a glass rod.

Martin particularly recommends the application of the iodine salt first to the paper, drying this, then applying the argentine solution, and drying rapidly. I have urged the necessity of this on several occasions : the advantages are, that the iodide of silver is left on the very surface of the paper ready for the influence of the slightest chemical radiation.

The productions of M. Flacheron, which were seen in the Great Exhibition, excited much interest, and the process by which these were obtained in the Eternal City was eagerly sought for by photographic amateurs. In the Art Journal for May. Mr. Thomas has communicated the process by which the photographers of Rome produce their best effects; and as this is important, as being useful in hot climates, a sufficient portion of that communication is transferred to these pages.

1st

Select old and thin English paper—I prefer Whatman's: cut it in such a maimer that the sheet shall be the sixteenth of an inch smaller than the glass of the paper-holder on every side, and leave two ends at diagonal corners to the sheet by which to handle it.

2dly

Prepare the following solution:— " Saturated solution of iodide of potassium 2 1/2 fluid drachms: pure iodide 9 grains: dissolve.

" Then add, distilled water 11 1/2 ounces, iodide of potassium 4 drachms, bromide of potassium 10 grains, and mix. Now, filter this solution into a shallow porcelain vessel somewhat larger than the sheet of paper to be prepared. Take a piece by the two diagonal ends, and gently place the end of the marked side nearest to you, upon the surface of the bath ; then carefully incline the surface of the sheet to the liquid, and allow it to rest two minutes; if French paper, one minute, or until the back of the paper (not wetted) becomes tinted uniformly by the action of the dark-coloured solution. Raise it up by means of the two ends occasionally, in order to chase away any air-bubbles, which would be indicated by white spots on the back, showing that the solution in these parts has not been absorbed. Hold the paper by one of the ends for a minute or so, in order that the superfluous moisture may run off, then hang up to dry, by pinning the one end to a string run across a room, and let the excess drop off at the diagonal corner. When dry the paper is ready for use, and quite tinted with iodine on both sides. It will keep any length of time, and is much improved by age.

3dly

I will presume that four sheets are to be excited for the camera, and that the operator has two double paper-holders, made without a wooden partition, the interior capacity of which is sufficiently large to admit of three glasses, all movable. The third, as will be seen, is to prevent the two pieces of excited paper coming in contact with each other.