Local bleaching, method

There are three methods for bleaching prints overall, local, and spot. 

Local This is the method for control work on comparatively large areas. Bleaching is done with a small wad of cotton or a brush. Local reduction can brighten specific areas, put luminosity into shadows, or drastically alter tonal values. 

If, by absorption of monochromatic light, i.e. a laser beam, a molecule can be so modified in its structure or in its interaction with the local environment that a laser pulse of the same wavelength cannot - even at a later time - again be absorbed (bleaching), then this molecule is excluded from the ensemble of molecules which contribute to the broad, inhomogeneous absorption line. In the broad absorption band, a hole then appears at the position of the individual absorption of the bleached molecule. This forms the basis of the method of hole-burning (cf Fig. 12.17). 

The Lancet s commissioners began their inquiries in Newcastle and based them on personal inspection of the men employed in the packing of bleaching powder, the study of the records of Newcastle Infirmary, and consultation with local medical men. They concluded that by none of ese methods could we establish anything definite against the chemical works . In Lancashire, they found nothing definite from the men , and local medical opinion very much divided on the issue. Dr. Angus Smith informed them that he had also received very contradictory accounts of the matter, and as yet no definite evidence . The Lancet concluded that the question of the effect of alkali manufacture on health... 

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