Blue-black tones

The antifogging effects of BZT are greater than bromide, especially in developers of high pH. As a result, BZT is especially useful for salvaging outdated papers or when blue-black tones in prints are desired. 

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 . 

One of the best methods to achieve blue-black tones is to use gold chloride. Not only does the gold chloride tone the print to various shades of blue, it also serves to protect the silver from degenerating. 

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. 

The same treatment can be applied to chloride and chlorobromide papers to eliminate any greenish black tendencies and/or achieve a blue-black tone. 

Blue toner for solid deep blue tones on warm-tone papers, and soft blue-black tones on neutral-tone papers. 

Using the Toner. Immerse the well-washed print for 10 minutes at 68F/20C or until a just perceptible blue-black tone appears. Then immerse in a washing aid and wash for 1 hour. 

Toning time can be increased up to 20 minutes for increased blue-black tone. 

This bath can be used directly on a print to produce a blue-black tone. It may also be used on prints that have been toned in any of the preceding methods. The toned print is first immersed in a 3% sodium chloride solution. 

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 classic formula for gold protective toning is Kodak GP-1 Gold Protective Solution. Like selenium toner, GP-1 not only protects the print but causes a minimum color shift. What shift there may be is toward a slight blue-black that some photographers find pleasing. With some papers, GP-1 will also improve separation in the highlights. 

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. 

NOTE 2 If a stock solution is made up with no bromide or benzotriazole it can be varied from a cold/blue black developer to a warm-tone developer with the addition of benzotriazole or bromide. 

Iron blue pigments are used to impart a pure black tone and high jetness in printing inks. They are used in paints with deep blue colors but seldom used in tints. Use of these pigments has been greatly reduced due to the availability of more durable copper phthalocyanine blue pigments. 

Jet ljet n [ME, ft. MF jaiet, fr. L gagates, fr. Gk gagates, fr. Gagas, town and river in Asia Minor] (14c) Term used to describe the blackness or intensity of the mass tone of black or near black surfaces. It is frequently used to describe dark blues, blue-black or black pigments. (Billmeyer FW, Saltzman M (1966) Principles of color technology. Wiley, New York). 

Some of the color deficiencies can be overcome by using a fourth ink, black, which allows printing neutral tones and dark blacks and colors. Black also improves the contrast of an image and its apparent sharpness. Black, usually referred to as K to distinguish it from blue, makes up the fourth member of the printer s primaries, CMYK. 

Iron Blue. There are three common varieties of iron blue MUoti, Chinese, and Pmssian (they are sometimes caUed toning blues). The three types differ chiefly in color, ease of dispersion, and reactivity characteristics. MUori blues are the easiest to disperse and are the least reactive. They are reddest in mass tone (plum colored) in tints, they ate intense and intermediate in redness between the Chinese and Pmssian varieties. Both the Chinese and Pmssian blues are jet in mass tone, but Pmssian blue is considerably redder and less intense in tint than Chinese blue. Because of their jet mass tones, both are used to shade blacks. Pmssian blues are the hardest to disperse and are somewhat more reactive than Chinese blues. 

Commercial flushed pastes commonly contain about 40% pigment however, these products are standardized not in terms of pigment concentration but regarding their tinctorial strength. The ratio between carbon black and Alkali Blue pigment in a toned product may range between approximately 2 1 and 4 1, depending on the nature of the components and on the desired effect. 

FIGURE 2.22 The three-dimensional CIELAB colour system. Left /zab (hue) describing the tonality of the color, where 0° corresponds to red, 90° corresponds to yellow, 180° corresponds to green, and 270° (or —90°) corresponds to blue, C represents the chroma (or saturation), where 0 is a gray tone, while 100 is a pure hue. Right the lightness (L ) goes from black (0) to white (100). 

Iron blue pigments are used in the manufacture of single- and multiple-use carbon papers and blue copying papers, both for toning the carbon black and as blue pigments in their own right [3.180]. 

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