Stabilization Methods for Black-Dyed Silk Used for Seals Attachment

Textile cords and ribbons are an integral part of archival documents with pendent seals. These textiles are frequently highly degraded, especially in case of black-dyed silk. However, their maintenance in good condition is necessary for retention of the seal and thus the legal value of the document. Methods of chemical stabilization of iron-gall inks on a paper support are promising also for stabilization of degraded black-dyed silk. This chemical stabilization is based on deacidification or the use of antioxidants or a combination thereof. The deacidification is potentially dangerous for silk because of its high stability in the slightly acidic region. Therefore the stability of silk in the alkaline pH region was measured and even long-term immersion of silk in a medium with pH 9 did not result in degradation changes. The selected reagents (methoxymagnesium methyl carbonate, tetrabutylammonium bromide, cysteine, calcium phytate and tannin) were tested. The effect of stabilization procedures was studied on artificially damaged samples of black-dyed silk containing unbound ferrous ions. The effectiveness of the stabilization procedures and their influence on the long-term stability of silk were evaluated by means of colorimetry, mechanical properties (flexural rigidity, thread tensile strength), measuring the pH of the silk surface and scanning electron microscopy.