Saturated Solution of Iron,...................................

4 ounces

Methylated Spirt,........................................................

4 ounces

Glacial Acetic Acid,..........................................

4 ounces

Bottle filled up with Water,..........................................

80 "

Now that nitrate of baryta is used in the bath (ten or twelve drops of saturated solution in a 12 x 10 bath), probably more plates could be done; but it is usual to discontinue the use of the bath as soon as it is found difficult to keep the developer on the plate. Probably about 170 or 180 plates may be done before this happens. A bath holding 80 ounces of solution 35 grains to the ounce, when it was discarded as worn out, was found by the argentometer to register 16 grains; it had also diminished in quantity nearly one-third. The number of plates sensitized in it was about 180 7 1/2 x 7 1/2.

Quantity of Silver at first,..........................................

2,800 grains.

Quantity in the Bath left,............................

880 "

Quantity used,..........................................

1,920 "

Practically about ten grains a plate; about two cents' worth of silver, or six cents a square foot. With a bath made of new silver and water, the plates at first come beautifully bright; but rapidly a surface fog accumulates, which gets worse and worse with every plate that is put in the bath. When this occurs, the bath has to be taken out, and a few drops of a saturated solution of baryta added, and stood in the sun for a day or two, when a deposit takes place, and, after filtering, the surface fog never appears again. In the former case, when the surface fog is rubbed off, the film under is bright, like bare glass, whilst in the latter, after the addition of the baryta, the film is granular, looking something like very fine ground-glass. The glass plates are all albumenized before coating with collodion; probably this has something to do with it. In every case the development is pushed to the utmost. The fog here spoken of would not be noticeable in a negative, nor the granular film; but in the case or transparencies for the lantern, where absolutely bare glass is needed, it is very obvious.

170. And not only does tot collodion sometimes cause very annoying troubles,but it is subject to annoyances which either impair its value as a helper or render its work useless altogether.If it is suffered to evaporate, it becomes thick and unmanageable. Should it is suffered kept too long before use it becomes red, thick, and works with too great intensity. When it is salted in a certain way, it may not be need with good results until it is several days old. If diluted, or impure chemicals are used in its mixture, it will rebel; and if the bath is not in harmonious condition there is no end to the troubles which will occur.

Adding more nitric acid to the bath did not diminish the surface fog nor the granularity of the film. Adding iodine to the collodion did tend to clear the film, particularly the granularity, but did not remove it unless an enormous quantity was added, making the collodion quite dark, in which case the exposure was very much lengthened, and the resulting image very weak. The best result was obtained with the collodion a dark sherry color. - R.Gillo

170. I have suffered great annoyance from collodion admirable in every way except being too thick, thus making it impossible to flow a plate evenly. The trouble was intolerable when I had occasion to make a picture with a delicate sky. I tried to remedy the evil by reducing the collodion with alcohol, but it was always at the expense of sensitiveness, making the exposure necessarily longer and the resulting negative very inferior. I then tried equal parts of alcohol and ether. I found that better than the other, but by no means satisfactory.

This state of affairs had cost me a good many pounds of collodion, perfect in every respect except in being too thick, when the query arose in my mind, "What does a perfectly balanced collodion lose first, when it begins to deteriorate?" "Why, ether, of course" answered reason; "and it wants ether to replace that which is lost." I tried this with perfect success, and now find a bottle of good ether one of the every - day necessities in my practice.

I mention this because I have been much tried and could find no remedy. 1 have been alcohol alone recommended, and equal parts of ether and alcohol, too; but my experience is that a perfectly-balanced collodion, when it is new, wants ether when it gets thick. Add from day to day as you see it. It is a perfect cure. - B. W. Kilburn.

Structural Crapy Limbs. - Marks from glutinosity will sometimes occur when using cadmium as an iodizing solution. A sample of plain collodion which gives these markings will probably be free from them after keeping for a few months without any further treatment. Structural lines on the film also frequently depend upon the plate not being properly-rocked whilst pouring off the collodion. Some operators dilute glutinous collodion with ether, but in doing so there is always danger of precipitating the iodide of potassium, and. if the pyroxylin be of that kind which sets very rapidly, the use of too large a proportion of ether will produce markings of a different kind. - T. Frederick Hardwich.

A source of great waste among photographers is that of old collodion.It can be renovated and used again by the following process: Pour off the collodion from the sediment, and add subchloride of mercury (Hg2 Cl) - calomel - until a greenish color is assumed when shaken. Then allow it to settle, and add more calomel until, by shaking again, the collodion appears of a canary-yellow color. Now, if it is very old and thin, either add more cotton to it or mix it with your new collodion. When thus treated, it will never turn red again.

171. Semi-zigzag lines, running from the edge of the plate that first enters the bath solution upwards, attract us next. These are also caused by a want of harmony between the bath and the collodion, but for a reason different from that which creates fog. If the collodion be too highly iodized to suit the strength of the bath, then these lines or marks will occur. The remedy is to test the bath, and add silver until it reaches the strength of a newly-made bath. Should the lines, after trial of a plate, still appear, then add plain collodion to the iodized, a little at a time, until the lines are no longer seen on trial of further plates.