Print bleaching, process

The archivally stable Cibachrome printing process is based on the use of developed silver metal in the negative image for the imagewise reduction of azo chro-mophores 39-41 to colorless anilines under highly acidic conditions. The anilines are then dissolved away to leave a positive image in dye. This process is also known as the silver dye bleach process [56,57],... 

Stopping the bleach process when some of the metallic silver is still visible will often create a deeper color than bleaching to completion. However, it is less controllable because the precise moment to pull the print may not be repeatable unless carefully timed. Partial bleaching may also create a split-toned effect that may, or may not, be desirable. 

To halt the bleach process use the hose, mentioned above, directly on the area being bleached. If a hose is not available, use a water-saturated sponge. After the bleach has been thoroughly rinsed with water, immerse the print in fixer for a few seconds to completely neutralize the bleach.You may repeat the bleaching process as many times as necessary. When the process is complete, fix in a fresh, non-hardening fixer and wash the print thoroughly. 

Most of the peroxodisulfate produced (>65%) is used as a polymerization initiator in the production of poly(acrylonitrile), emulsion-polymerized PVC etc. The rest is utilized in numerous applications (etching of printed circuit boards, bleaching processes etc.). 

Plastics can be used to make erasable printing media by a number of different techniques. Photo changing dyes could be incorporated into the structure of the plastics. The printer could change the dye to the colored form to read, and the material can be bleached with another unit that would reverse the photo coloring process. An ionic type plastic can be incorporated into the plastics and used to color the printed area by the use of an indicator type reaction with an organic acid or base. Another method would be to use a thermal printer in conjunction with liquid crystal type materials that would alter the state of the liquid crystals in the printed areas. Applying heat and electrical fields to the printed sheet would erase the printing. 

Bleached or unbleached kraft process wood pulp usually converted into paperboard, coarse papers, tissue papers, and fine papers such as business, writing and printing... 

The choice of the absorber dye is obviously defined principally by the wavelength of the laser used in the process. However, since some of the near-IR absorbing dye is likely to be transferred in the process, it should not interfere with the colours in the final print and preferably be colourless. Colourless near-IR absorbers are difficult to find and workers at the Imation Company overcame this problem by using an IR absorber (4.21), exhibiting broad absorption at 790- 900 nm and addressable at 830 nm, which bleached out during the process. ... 

Color-Dye Sensitization In Chapter 4, Film Development, I mentioned the use of color-dye sensitization to replace silver particles in him. Color-dye sensitization when applied to him is of questionable beneht to the photographer. However, when applied to paper it is not necessarily a bad thing. Color dyes enable the manufacturer to create papers with a fast printing speed and increased tonal scale. On the other hand, dye-rich papers do not respond as well to bleaching, toning processes, or direct image color manipulation through the use of print developers. This is doubly true of dye-rich papers with over-hardened emulsions which are discussed next. 

Uses Principal use is in bleaching baths iron printing processes and as a bleach before sulfide toning. Also used in dye-toning formulas. 

Expose and process the print as normal and wash well. Bleach the print, wash until all the yellow from the bichromate has been removed from the highlights, and redevelop in the following developer. 

Mitsubishi Chemical Corp. developed a water-based ink composed of photo-chromic-containing capsules and an aqueous polymer binder.46 The average particle size of the capsules containing photochromic spirooxazine and antioxidant was 20 pm. By using this ink composition, cotton clothes could be screen printed. The printed part showed coloration within 10 s when exposed to sunlight and exhibited good fatigue resistance. Furthermore, it bleached within 15 s in the dark, and this process was observed repeatedly. 

The first step in the restoration process is dry cleaning with soft erasers. Old mounts or supports, usually highly acidic, are removed. Immersion in water is prescribed for removal of discoloration in the more stable forms of art on paper etchings, prints, engravings, and some drawings. For specific stains that cannot be removed with water or other solvents, bleaching agents are applied locally. Deacidification by total immersion is preferred a spray is used when this is not possible. 

Most natural fibers, such as cotton and linen, have a yellowish look when they are first manufactured because of the presence of natural impurities. They must be bleached to pure white before they can be dyed, printed, or sold as white fabrics. The commercial process of bleaching these fabrics is very similar to the process you used in this experiment. 

---