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Re: Permanency of VDB (test)
Sam Wang wrote:
> At 8:14 PM -0400 7/19/00, Robert W. Schramm wrote:
> >>it seems has to do with the deterioration of the image due to
> >>chemical reactions between those comound which make up the image
> >>and chemical compounds in the substrate and in the air.
> Which begs the question again, what if we wax the VDB print with
> Renaissance or similar wax? What if we coat and protect the VDB with
> a layer of colloid such as gum or gelatin? I'm testing the latter but
> it will take awhile to get answers. Problem is, in the humid South,
> even toned gelatin-silver prints are sometimes attacked by fungi and
> Sam Wang
According to L>P> Clerc in "Photography Theory and Practice" 1937,
photographs on POP or developement papers may be effectively protected
against atmospheric action by waxing. The waxing solution may be
prepared by melting paraffin-wax on a hot iron and letting it run into
petrol. on cooling it will have the consistency of a thick cream.
Another way to give a certain degree of depth to to the blacks of matt
prints is by treating them(by means of an airbrush or atomizer )with a
thin solution of gum arabic, but this gum, unlike the wax does not
afford any protection to the print.
Gradual fading of the image is generally caused by incomplete removal of
the hypo which under the influence of oxygen and moisture gives rise to
sulphuric acid which attacks the silver image. Discoloration of the
whites is due to incomplete fixing.