Preservation

Methylene blue testing (implementation underway)

  • ISO 18917 1999 compliance: Methylene blue testing to measure residual thiosulfate and its decomposition products is of use in appraising the adequacy of washing and therefore the permanence of the silver image on photographic films, plates and papers. Inadequate washing can cause a loss in image density and the formation of stain in low-density areas.

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The U.S. National Archives and Records Administration
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