Chapter 12
Copying and Restoration

(This chapter was written in collaboration with R. Gilliam Rudd)

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Copying valuable old photographs in a collection should have a high priority, to obtain more stable reproductions before the originals deteriorate further. It is beyond the scope of this book to cover copying in detail. However, some useful techniques are touched on that are especially applicable to stained or faded pictures.

As to the choice of film sizes most suitable for copying, it can be said without question that the best size is the largest practicable a budget will allow. The 35mm film format with a good camera and a lens designed specifically for copying, along with the recently introduced films such as Kodak Technical Pan, can indeed yield copies of excellent quality from originals that vary widely in quality. The copy film needs to have extremely fine grain and a wide contrast range. However, it is more difficult to avoid scratches and surface dust in 35mm negatives in roll format than in flat sheet film.

4x5 sheet film is probably the most widely used size because with reasonable care the negatives can be individually filed and printed repeatedly without damage to the surface. Moreover, it is available in a range of contrasts and color sensitivities.

Deterioration with age in old photographs takes several forms, and more than one form may occur in a single photograph. Chemical treatment and physical retouching are sometimes effective but they do require considerable skill and may be destructive or irreversible. Restoration, therefore, should first be practised on a copy. Copying is a passive procedure resulting in no damage to the original.

Paper prints commonly exhibit the following types of damage:

Type 1. Color changes in the image or in the paper support, sometimes becoming brownish or yellow.
Type 2. Staining, appearing as an irregularly-shaped area of color, the color depending on the cause.
Type 3. Fading of the image.
Type 4. Tarnishing of the darker portions of the image, resulting in near specular surface reflections.
Type 5. Surface abrasion and tears.

The recommended copying techniques for these conditions are as follows:

Type 1. Use high-contrast film such as Kodak Contrast Process Ortho 4154. following the manufacturer's development recommendations to modulate contrast as needed.
Type 2. Stains that are a different color than the image may be reduced or eliminated by copying with a filter close to the stain color. If the color of the stain is nearly the same as that of the image, it will be fundamentally difficult to separate the two. If there are perceptible color differences, separation may be possible through selection of adjacent filters in a close series such as the Kodak Wratten filters. It may also help to use a panchromatic film instead of an orthochromatic film.
Type 3. Treat like type 1, plus a filter complementary to the image color. For example, if the image is brownish or yellow, use a deep blue filter such as Wratten 49.
Type 4. The degree of tarnish sheen can be reduced during copying by altering the angle of illumination, or with polarizing filters, or both. A polarizing filter should be used over both the light source and the copy lens, with polarizing axes adjusted for optimum effect. However, this technique should be used only if the sheen significantly obscures detail in the original, since the resulting copy is not a faithful reproduction of the original. Glass-covered Daguerreotypes and ambrotypes can be copied with polarizers to reduce glass reflections without dismantling the cases, since such reflections often do obstruct details. However, the images in these two types are very sensitive to viewing angle and illuminating angle, and a careful balance is needed in the copying conditions.
Type 5. Techniques recommended are: diffuse illumination, crossed polarizers, physical repair, and retouching copy prints.

Processing

All processing should be done in accordance with currently accepted archival procedures. In recent years more effective materials and processes for improved archival life have been published in the technical literature and in symposia. Accelerated testing methods for evaluating these procedures have gradually evolved, with encouraging correlations. But the technology is advancing rapidly, and it is important to keep abreast of currently accepted practices.

Following are some useful references for further reading:
Ref. 36, Conrad
Ref. 46, Eastman Kodak
Ref. 59, Gassan
Ref. 76, Hendriks
Ref. 122, Reilly
Ref. 130, Rudd