Surface soil, soot, and grime were present on the rectos and versos of the folios and the high humidity levels instigated mold growth. The mold fed on the parchment, causing red-brown foxing stains which were scattered throughout the parchment and a few areas in the paintings. The mold damaged parchment was spongy and weak (fig. 2). Old attachments, gummed brown paper tapes and tabs of pressure sensitive foam tapes, were attached to the top and bottom verso edges of the folios for mounting the folios onto backing boards. The attachments caused localized staining, locally intensified parchment distortions, and the gummed adhesive provided an additional food source for the mold. The thickly applied media was beginning to crack, flake, and powder in areas and was the most concerning condition issue. In the case of the folios, expansion and contraction of the parchment in response to fluctuating humidity levels, was constantly inflicting stresses on the physical bond between the paint and the parchment. The physical tension induced detachment and minor losses of the paint from the parchment. Powdering of paints, which was also observed in the folios, occurs when there is not enough binder to hold the large pigment particles together or if the binder degrades, no longer providing the necessary cohesion. In the 1400s, paints were made by hand by the artist or their studio which meant that the results were less standardized. Making a paint with enough binder required experience and sensitivity to materials. Improper binder to pigment ratios is a common condition issue for pigments with larger particle sizes. Examples of such pigments used for manuscript illuminations are malachite, azurite, vermillion, and ultramarine. Examples of media damage are shown in the slideshow below.

Surface Cleaning and Structural Repairs Surface soil and mold residues on the parchment rectos and versos were reduced with a kneadable eraser, avoiding all media. A microscope was also used in this step for accuracy. Accretions, which are surface deposits of foreign materials, were reduced mechanically with a scalpel. Old paper attachments were removed from the versos of the folios using a heated spatula to remove the foam tapes. A 4% (w/v) methylcellulose aqueous poultice was used to remove paper tapes. This was followed with a gentle enzymatic solution applied by cotton swab to reduce gum adhesive as best as possible without introducing too much moisture to the parchment. Small tears in the parchment were mended with Japanese Kozo (paper mulberry) tissue paper adhered with 5% (w/v) gelatin or wheat starch paste.

Reduction of Planar Distortions The distortions in the folios prevented safe matting and framing of the works because the surface of the paintings would touch the glazing. Contact with the glazing could cause further media damage and loss. Planar distortions in paper and parchment supports are reduced by relaxing the fibers and slightly expanding the hygroscopic supports with controlled introduction of moisture followed by drying under pressure or tension. Exposure time and the methods for introducing moisture are also important for success. Parchment supports pose an additional challenge because of their extreme reactivity to moisture. If parchment becomes too wet, it can easily revert to raw flesh. Most importantly, humidification and flattening should not cause damage to the support and media, so the conservator must choose techniques keeping the vulnerabilities of the artwork in mind. The goal of this treatment step was not to completely flatten the folios but to reduce the distortions enough to safely mat and frame the folios. The humidification of the folios needed to be done very gradually to avoid disturbing the fragile attachment of the paint layers to the parchment. A humidity chamber was used to humidify each folio because it offers the most control over the introduction of moisture and allows the work to be monitored during the process. The folio was supported by a screen over a reservoir of deionized water in a tray. Plexiglas was placed over the tray to seal it and allow humidity levels to rise. Tension drying was chosen to flatten distortions. Linen threads were attached at even intervals along the verso edges of the folios using 8% (w/v) gelatin. Threads would also be used in a later step to mount the works for display. After a brief thirty minutes of humidification, the folios were removed from the chamber and dried under tension. The free ends of the threads were secured with masking tape to an 8-ply window mat ‘stretcher’ to relax distortions (fig.10 a-b) as the parchment dried. The threads were examined periodically as the parchment dried, adjusting the tensions as needed.

Cosmetic Treatment Once the chemical and physical stability of the folios was ensured, cosmetic treatment steps were completed to address issues that were disrupting the aesthetic appreciation of the work.. Darkened lead white was converted from lead sulfide to lead sulfate using a 3% (w/v) solution of hydrogen peroxide at pH 8. The solution was brush-applied in very small quantities using a microscope to ensure accurate application and to monitor the reaction. The shift of the darkened lead white from black or dark gray to pale gray or white, significantly improves the appearance of the image and, most importantly, honors the artist’s original intent. The most notable results are seen in St. Margaret of Antioch and St. Pope Urban (fig. 11 a-b, fig.12).