Papers bromide

Many toning processes in photography involve the use of selenium compounds.6 One such process recently recommended consists in treating the print or lantern slide, after developing, fixing and washing, with a solution containing about 1 per cent, of crystalline sodium sulphide and 1 per cent, of sodium selenite or selenious acid after twenty minutes or so in such a bath intense brown tones are obtained with chlorobromide papers, or brown-violet tones with pure bromide papers.7... 

Many modifications of the apparatus and method have been recommended.1 Discs of paper may be fixed across the mouth of the tube B in various ways and the stain, thus localised, is uniform in colour and sharp in outline and therefore more readily compared with standards.2 Mercuric bromide papers are satisfactory in use,3 but should be freshly prepared the stains may be developed in aqueous potassium or cadmium iodide and compared with a colour standard.4... 

Photosensitization. Bon (Bll) proposed the following method. Press the wet strip against silver bromide paper, expose for a short period to light, develop with a hard developing bath, and fix immediately with concentrated potassium metabisulfite. Protein at 1 (xg/mm3 gave a distinct spot on the photographic paper. 

Bromide papers are generally the most sensitive to light and almost always give neutral or cold (blue-black) tones. They are the best papers with which to achieve cold tones through direct development, as opposed to toning after development. Bromide papers include Kentmere Bromide and Slavich Unibrom 160 . 

This information can be quite useful. For example, giving a print more than the usual exposure and developing it for less than the normal time, say 45 seconds to 1 minute, will often enhance warm tones, especially with chlorobromide papers. Using a warm-tone chlorobromide paper and developer combination will further heighten this effect. With bromide papers the results may be less than satisfactory as the color may be muddy olive depending on the paper. 

There are three ways to achieve cold tones. The first is through direct development of bromide paper. The second is through the gold-toning of a warm-tone chlorobromide paper. The third method is immersion in a blue-toning bath (Formulas Toners, Ansco 241 Iron Blue Toner). 

Method 1. The classic developing agent for creating cold tones on bromide papers is amidol. However, PQ developers using organic antifoggant, such as benzotriazole, will also increase the amount of cold image tone in a print (Formulas Paper Developers, Blue-Black Developer). In either case the results are usually very subtle. 

The best papers to use with amidol developer are old-style, soft emulsion papers, such as those with minimal hardener, silver-rich papers (papers without excessive dye sensitization), graded bromide papers, long-scale chloride papers, or specially coated papers such as David Lewis Bromoil Paper (see Resources). With any other paper, which is to say most modern chlorobromide papers, amidol works just as well, though not necessarily better than most other developing agents, or combination of developing agents—thus the controversy. 

Papers of the slow chlorobromide variety will be more successful for blue toning than fast chlo-robromide or bromide papers. 

Chromium Intensification for Prints The technique is to bleach the print and then redevelop it in a non-staining developer, just as you would for a negative. Slow chlorobromide and chloride papers respond best to this technique. Cold-toned and bromide papers don t respond as well to chromium intensification, but changes will occur. If in doubt, give it a try. 

Uses Hardening and acid fixing baths stop baths as a clearing bath after ferrous oxalate development of bromide paper. Glacial acetic acid can be used as a solvent of gelatin, celluloid, and pyroxylin. 

Notes Amidol is one of the finest developing agents for blue-black tones on soft-emulsion bromide paper. It is also capable of creating neutral-blacks with a fine scale and transparency in the shadows. 

Notes When blue-black or cold-black image tones are desired with bromide papers, benzotriazole should be used in addition to, or substituted for, potassium bromide. Make a 0.2% solution of benzotriazole (2.0 grams benzotriazole in water at 125F/52C to make 1.0 liter) then reduce the bromide to 1/10 or 1/6 strength and use just enough benzotriazole solution to prevent developer stain or fog. A little experimentation will be required. 

This formula gives either blue-blacks or rich, neutral tones, depending upon the paper. It works best with bromide papers. 

Normal dilution is 1 1 with water. For high contrast, use full strength for low contrast, use 1 2 with water. The useful development range with bromide papers is 2 to 6 minutes. With chlo-robromide papers it is 1 G to 3 minutes. 

Dilution may vary from 1 1 to 1 4 depending upon the contrast and image tone desired. Normal dilution with chlorobromide papers is 1 2. For warmer tones, dilute 1 3 or 1 4 and add approximately 8.0ml of 10% potassium bromide per liter. For higher contrast with bromide papers, dilute 1 1 and add 1.0 ml of 10% bromide per liter. 

For warm black tones with bromide papers dilute 1 3. 

For warm black tones on slow chlorobromide and chloride papers and neutral tones on bromide papers. 

Use a 3 minute standard development time for amidol developers with bromide papers. 

This famous teaspoon formula first appeared in Practical Photography No. 5 in 1935. It is a good developer for bromide papers and is often recommended for bromide enlargements that are intended for the Bromoil process. 

Use Photography (gelatin bromide papers and plates), process engraving and lithography, special soaps, spectroscopy, infrared transmission, laboratory reagent. 

Sinee also H2S gives a eolour reaction with HgBt2, it must be removed from the ASH3 stream before the eontact with the mercuric bromide paper. Hydrogen sulphide is absorbed by cotton wool and paper impregnated with lead acetate. PH3, SbH3, and GelTj also interfere in... 

Mercuric bromide papers. Place thin, compact filter paper disks (about 20 mm in diameter) in a freshly prepared 5 % HgBr2 solution in ethanol for 30 min. Lay the papers on a watch-glass to dry in air. The papers may be stored in an amber-glass jar for not longer than a week after preparation. 

Into the lower tube insert 50 mg to 60 mg of lead acetate cotton R, loosely packed, or a small plug of cotton and a rolled piece of lead acetate paper R weighing 50 mg to 60 mg. Between the flat surfaces of the tubes place a disc or a small square of mercuric bromide paper R large enough to cover the orifice of the tube (15 mm x 15 mm). 

In the conical flask the prescribed quantity of the substance to be examined is dissolved in 25 ml of water R, or in the case of a solution, the prescribed volume is adjusted to 25 ml with water R. 15 ml of hydrochloric acid R, 0.1 ml of stannous chloride R, and 5 ml of potassium iodide solution R are added. The solution is allowed to stand for 15 min and 5 g of activated zinc R is then introduced. The two parts of the apparatus are assembled immediately and the flask is immersed in a bath of water at a temperature such that a uniform evolution of gas is maintained. A standard is prepared in the same manner, using 1 ml of arsenic standard solution (1 ppm As) R diluted to 25 ml with water R. After not less than 2 h the stain produced on the mercuric bromide paper in the test is not more intense than that in the standard. 

Swan, Sir Joseph Wilson (1828-1914) English chemist and physicist who in 1860 invented the electric lamp 20 years before Thomas Edison. In 1864 he patented the carbon process for photographic printing in 1871 he invented the dry-plate technique and in 1879 he produced bromide paper. He was the first to produce a practicable artificial silk. 

Fluorescein provides a specific reaction for bromine and iodine chlorine can also be detected if the other halogens are absent. The yellow dye reacts with free bromine to produce red eosin (tetrabromofluorescein), whereas iodine yields red-yellow erythrosine (tetraiodofluorescein) (see page 145). Chlorine is without direct action on fluorescein. If, however, a mixture of potassium bromide and fluorescein is used, the bromine set free by the chlorine immediately forms eosin. Thus fluorescein also provides a test (indirect) for chlorine. All these tests can be carried out as spot reactions on fluorescein and fluorescein-potassium bromide paper. 

If the response is negative, a drop of the test solution is placed on fluorescein-potassium bromide paper. If chlorine is present, a red spot results. 

Reagents 1) Fluorescein paper Strips of filter paper (S S 598g) are bathed in a saturated water solution of fluorescein and dried 2) Fluorescein-potassium bromide paper Strips of filter paper (S S 598g) are bathed in a very weakly alkaline solution containing 0.1 g dye and 0.5-0.8 g KBr and dried... 

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