In the 1960s, a company by the name of Ciba-Geigy in Switzerland created a new process for printing a color transparency directly onto paper without the need to produce what is known as an internegative (the production of a negative from the positive film). This paper was formally known as Cibachrome, though was purchased by Ilford. The Cibachrome successor is Ilfochrome Classic - though is occasionally confused with Ilfochrome Rapid.

Most prints made today are produced using a chromogenic process where the dyes used to color the paper are part of the 'chemistry' (in darkroom parlance, the chemistry is the set of all of the chemicals used). These chemicals interact with the developer on the paper to form a color image.

With Ilfochrome Classic, the dyes are part of of the paper itself and are bleached out selectively as part of the process. The dyes used are known as AZO dyes which are well known for stability and purity. This gives the Ilfochrome Classic prints archival quality and rich color. This proves to be extremely fade resistant - where a normal print will fade over time, the Ilfochrome prints will last for decades or more. Having the dyes embedded in the emulsion, this acts as an anti-light scattering layer when making the print, preventing the projected image from scattering within the emulsion itself and producing a much sharper image.

An additional impact of the AZO dyes being used is that they are pure metallic and have no organic component (opposed to AZO-methane or indo-aniline dyes used in chromogenic systems - these contain residual color couplers that may discolor with time). The life expectancy of the print is longer than any other conventional process and Ilfochrome Classic Deluxe Glossy Prints are guaranteed to not fade or discolor for 200 years. Thats 200 years! For this guarantee to be in effect, the prints must be on Ilfochrome Classic CPS 1.k normal contrast paper or CF.1k low contrast paper and must be professionally laminated with a protective polyester film. This guarantee is not applicable to prints that are displayed outdoors or where exposed to atmospheric pollutants.

While the paper is more expensive, there are cost savings in the chemistry itself - less is used. With standard color prints, there is a significant amount of toxic dyes that are left over after the print is made that must be disposed of. With Ilfochrome Classic, the developer is more similar to that used in the black and white process where the bleaching step can be neutralized simply (sulfuric acid neutralized with sodium bicarbonate) and contains no toxic substances. The fixer is also processed after use to remove silver.

To produce an Ilfochrome Classic print one must start with a positive film (not a negative film). This is often known as "slide" film and produces an image that is what was taken of rather than having the colors reversed. In theory, one could produce a print using positive paper and a color negative - though the question of "why" will rapidly be encountered - this would produce a print that would look exactly like the negative.

When printing a positive, spots or dust on the film will show up as black on the final print. This makes it very difficult to retouch to bring it back to the correct color (the negative process creates a white spot which can easily be painted over to correct the color). While it is possible to selectively bleach the spot and then redye it, this involves sulphuric acid and may be very damaging to the print (or the person doing the retouching). Ilford does make retouching dyes and Marshall Liquid Dyes for hand tinting can also be used for retouching light spots. Both of these are water soluble and can be washed off and reattempted.

In most cases, the paper used has either a glossy or pearl surface with either a white opaque polyester backing or a resin coated paper backing. However, there is a line of Ilfochrome Classic that is printed on a clear or translucent polyester film. The classic application of this is to produce an overhead transparency or a transparency for a light box.

The paper's structure is:

  • Protective layer
  • Blue sensitive emulsion without dyes
  • Blue sensitive emulsion + yellow dyes
  • Mask Layer
  • Interlayer
  • Green sensitive emulsion + magenta dye
  • Interlayer
  • Red sensitive emulsion + cyan dye
  • Resin coated paper with backing layer
Even with the protective layer, the Ilfochrome Classic is sensitive to the oils naturally on one's hand. Fingerprints will eat into the emulsion of the photograph and are very difficult at best to remove. Photographs should be handled only when wearing cotton gloves. If a print does get onto the photograph, use a soft cotton cloth to wipe it away. Denatured alcohol or PEC-12 film cleaner is also useful for removing prints.


http://www.lightroom.com/lr_pages/ilfo_info.htmlO
http://www.ilford.com/html/us_english/prod_html/ilfoclassic/Iclassic.html
http://www.hollandphoto.com/ilfoadv.htm

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