Archival Washing and Permanence

Printing

The Importance of Thorough Washing

The primary cause of image degradation in silver photography is the presence of residual chemicals -- specifically silver-thiosulfate complexes and unreacted thiosulfate (fixer).[1] Over time, these chemicals react with the silver image, causing staining, fading, and "bronzing." Archival washing ensures these residues are removed to levels that permit centuries of stability.

The Washing Process

1. Film Washing

Film is relatively easy to wash because the emulsion is thin and the base (polyester or acetate) does not absorb chemicals.

  • Conventional: 20-30 minutes in running water.
A U.S. Army lab technician washing photographic prints in a fine-weave screen basket placed in a flowing river, demonstrating that washing requires fresh moving water across the print surface
Washing prints in flowing water (Korea, 1951) — the principle is the same in any darkroom: fresh water must move across the surface for fixer to leave the fibers. Image: U.S. Army Signal Corps — Public domain
  • Ilford Method: Fill tank, 5 inversions, dump. Fill, 10 inversions, dump. Fill, 20 inversions, dump. This is highly water-efficient and effective.

2. Paper Washing

Paper is much harder to wash because the paper fibers (in Fiber-Based paper) absorb fixer deeply. Resin-Coated (RC) paper washes like film (5-10 minutes) because the plastic coating prevents absorption.

Using Washing Aids (Hypo-Clear)

Washing aids (like Kodak Hypo Clearing Agent or Ilford Wastaid) significantly reduce washing time and improve results. They work by ion exchange, replacing the stubborn thiosulfate ions with more soluble sulfite ions.

Archival Sequence for Fiber Paper:

  1. Fix: 5-10 minutes in non-hardening fixer (or two-bath fixing).
  2. First Rinse: 5 minutes in running water to remove surface fixer.
  3. Wash Aid: 10 minutes in Hypo-Clear with agitation.
  4. Final Wash: 30-60 minutes in running water at 20-25C.

Hardening vs. Non-Hardening Fixer

Hardening fixers (containing alum) make washing much more difficult. The cross-linked gelatin traps chemicals more effectively. For maximum archival permanence, use a non-hardening fixer unless the emulsion is very soft or the temperature is very high.

Testing for Permanence

  • Residual Hypo Test: Uses a drop of HT-2 solution (silver nitrate and acetic acid) on a print margin. A yellow stain indicates residual fixer.
  • Residual Silver Test: Uses a drop of ST-1 (sodium sulfide) to check if fixing was complete.

Tips for Success

  • Temperature: Water should be between 18C and 25C. Cold water (below 15C) is very inefficient at washing.
  • Agitation: Water must move across the surface of the print. Trays of stagnant water do not wash.
  • Siphon Washers: Use a dedicated print washer that ensures fresh water enters the bottom and overflows the top, preventing "dead zones."

References

  1. BOOK Haist, Grant. Modern Photographic Processing, Volume 2 1st ed. John Wiley & Sons, 1979. ISBN 0-471-04635-X. ↩