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Failures and Imperfections

On Glass. 1. Universal clouding from over exposure or diffused light in preparation or development of the plate, or alkalinity of the bath, or too much nitric acid in bath, or organic matter in the bath, or the used. colorless collodion; also vapors of ammonia or sulphuretted hydrogen. Such negatives may sometimes be recovered by the application of a weak solution of iodine, followed by hyposulphite of soda. 2. Spots upon the plate from excess of bromide of potassium in the collodion, impure nitrate of silver in the bath, super-saturation of the bath with iodide of silver, dust upon the glass or coating, the concentration of nitrate of silver by drying before exposure.

3. Curtain-like marks upon the edge, from the plate being too dry before dipping, not long enough in the bath to remove the greasy appearance. 4. Wavy lines, from the use of a glutinous, thick collodion from want of rocking when pouring off the collodion (common with cadmium sensitigus). 5. Rottenness of film, from bad cotton or dipping too soon after proving before properly set. 6. Oily lines, from the removal from the bath too soon. 7. Curved lines, from the developer not covering the whole plate immediately. 8. Silver stains, from reversing the plate between the bath and slide.

9. Yellow patches, imperfect removal of the iodide of silver in the fixing bath. 10. Scum upon the surface upon removal from the bath, over iodized collodion. 11. Image black and white without half tones, from under-exposure in the camera. 12. Collodion curls from the glass upon drying, from dirty glass, insufficient alcohol in the collodion, want of roughness of the edges of the glass. 13. Blueness of film, want of iodizer in collodion. 14. Crystals on film when dried, hyposulphite not washed entirely out. 15. Developer flows greasily, from want of alcohol in developer.

16. Circular transparent spots of large size, from pouring on the developer at one place.

On Paper. with some bars of zinc, and pour over it sulphuric acid largely diluted with water (1 of acid to 60 of water). As soon as it ceases to give off gas add more acid until the zinc is entirely dissolved.

Should any chloride remain add more zinc and acid. The gray powder is metallic silver, and may be run into an ingot in a crucible by mixing with twice its weight of carbonate of soda or borax. Hyposulphite Baths.

Boil for several hours with a suspended bar of zinc, filter out the precipitate, and fuse with carbonate of soda or borax. The button contains silver and gold if the solution has been used to tone and fix prints.

Toning Baths (Alkaline).

Add a solution of sulphate of iron, filter out and wash the precipitate; digest with diluted nitric acid for several hours; filter out the residue, which is metallic gold.

All waste solutions, containing silver, in the laboratory should be run into a large vessel, and acidulated with muriatic acid every evening, and the clear liquid siphoned off in the morning; the precipitates will be principally chloride of silver, and when enough has accumulated it should be removed from the vessel, and reduced, as advised for baths of nitrate of silver.

Paper Clippings.

The clippings of sensitized paper should be preserved, and when a quantity has accumulated burned to ashes; the ashes to be in a crucible, mixed with twice their weight of a mixture of carbonate of soda and borax. If carefully brought to a full red heat, and allowed to cool, the silver will be found collected into an ingot at the bottom of the crucible. It is best to trim the prints before washing or toning, but the whole of the cuttings are worth saving.

Removal of Silver Stains. 1. By rubbing with a moistened lump of cyanide of potassium, and washing freely with water. This mode is dangerous, on account of the highly poisonous nature of the cyanide. 2. By rubbing the spot with moistened iodide of potassium, then with diluted nitric acid, and then with hyposulphite of soda, and washing with water. 3. Apply a paste of chloride of lime for a few minutes, wash thoroughly with water; rub with moistened iodide of potassium, and dissolve out the iodide of silver formed by hyposulphite of soda. 4. For Linen or other Fabrics. - Rub with solution: Cyanide of potassium, 100 grs.; iodine, 10 grs.; water, 1 oz.; (very poisonous;) and wash with large amount of water. 1. Marbling and spots, from weak nitrate-bath. | TOOVELY'S (PATENT) PHOTOLITHOGRA- 2. Marbling after toning, from the prints overlying each other. 3. Spots by transmitted light, from imperfect removal of the silver salt. 4. Cold and faded appearance, from weakness of bath or excess of chloride in paper. 5. Yellowness, from acidity of bath. 6. Bronzing of deep shadows, negative is too transparent.