Conserving the Cosway Portrait of Shakespeare

Editor’s note: Folger conservators are internationally known for their expertise in book and paper conservation. When it comes to conserving paintings, though, we turn to outside experts like Dawn Rogala of Page Conservation, Inc. Here, Dawn explains how she treated the Cosway Portrait of Shakespeare. ¹ All photos in this post have been provided by Page Conservation. 

Using a binocular microscope to monitor progress removing one of the Cosway Portrait’s varnish layers

In April 2013, an eighteenth-century portrait of William Shakespeare believed to be from the collection of Royal Academician Richard Cosway (1742–1821) made its way from the Folger Shakespeare Library to the Page Conservation studios for conservation treatment.

Back view of the unframed panel

The wooden panel support is approximately 1/8″ thick, beveled on the reverse to 1/32″ thick at the edges. The wood is in good condition and there is no evidence of insect activity. Viewed from the front, the panel has a slight convex curve, and its fine diagonal grain runs from the top left to the bottom right of the composition.

A preparatory layer of white gesso (a smooth chalk-based coating) lies beneath the portrait and extends to the edges of the panel. The portrait is executed in oils, thinly applied with overlapping fine brush strokes and minimal impasto (paint applied thickly enough to stand up in relief). Close examination of the painting revealed surface abrasions in the background paint, most likely from previous restoration cleaning. Cleaning tests indicated that there was an upper layer of synthetic varnish over a yellowed natural resin varnish. Although some retouching was visible over areas of background abrasion, heavy layers of discolored varnish made it initially difficult to determine the extent of the earlier retouching. 

Cleaning tests before treatment

Above is an image of the Cosway Portrait before treatment, under normal illumination. The two small light areas on the left of the portrait are test cleanings that indicate the level of discoloration in the natural resin varnish.

Detail showing earlier retouching

Darkened areas of earlier retouching are visible beneath the discolored varnish in the background of the painting.

Examination under ultraviolet light

This image is taken under ultraviolet illumination. The heavy coat of natural resin varnish visibly fluoresces in response to ultraviolet radiation. (You can see that the two cleaning test areas do not fluoresce.) Retouching that sits atop an aged varnish usually blocks this fluorescence and appears as dark dots. In the Cosway Portrait, a few areas of retouching are visible on Shakespeare’s chin, but the painting’s thick varnish layer fluoresces so brightly in UV that it is difficult to identify any retouching beneath the varnish. Even the background retouching that is visible under normal illumination is not clear under UV. (Synthetic varnishes do not fluoresce under UV.)

Conservation cleaning of a painting is approached as an “unpacking” of obfuscating, non-original surface materials. Once the uppermost layer of materials is removed, the next layer may be accurately assessed and decisions made regarding how further cleaning should proceed. This careful progression may reveal previously unknown information, such as retouching obscured by heavy varnish.

Degraded varnish now removed from the left side of the picture

In this photo, the degraded upper synthetic varnish has been removed in an area on the left side of Shakespeare’s face. The very discolored underlying natural resin varnish remains and will be thinned in a balanced manner. Light areas in a portrait—such as the face, hands, and shirt collar—are often preferentially cleaned over the life of the painting and may appear too bright and out of balance with the rest of the composition. (Some pigments historically used to recreate a sitter’s blushing cheeks or warm skin tone are also light sensitive and fade over time, adding to the present-day ghostly appearance of some portraits.) Varnish removal on any portrait is a combination of science and aesthetics, as original materials must be preserved while non-original materials are reduced to bring the composition back into visual balance.

Detailed brushwork begins to emerge

In the image above, the artist’s detailed brushwork on the face is revealed during thinning of the portrait’s discolored natural resin varnish.

After removal of old inpainting in the background

Above is a fuller view of the portrait after thinning the discolored varnish and removing the earlier background repaint. This older repaint no longer matched the background color once the discolored varnish was thinned. The abraded paint beneath the old retouching is now visible. A thin layer of new, non-yellowing varnish was applied to isolate new inpainting from the original and to saturate original colors to aid accurate inpainting. Small dots of non-yellowing conservation colors carefully placed within areas of paint loss (not over original material) restore the background’s coherence.

New inpainting of the background

Using a magnifying visor, the conservator inpaints the abraded background of the Cosway Portrait with easily reversible synthetic conservation paints. A second layer of synthetic conservation varnish was applied after inpainting. This final layer preserves the saturated inpainting colors and imparts a satin sheen that enhances legibility of the portrait.

Close-up after cleaning, varnish removal, and inpainting

After treatment, the artist’s delicate brushwork in both the portrait and the background is newly visible.

The conserved painting, ready to return to the Folger