Reversible Modification Of Flexural Rigidity On Dry Archaeological Leather From Wet Anaerobic Burial Sites: An Herbal Method Irma

摘要

This work is based on a treatment reported in the article “Über der Weichen trockengefallenerAlkohol und Formalinpräparate, Herbarblätter und von Tapagewebe” in Der Präparator from2001 by Klaus Weichsler and co-authors. A series of experiments were performed toinvestigate the described effect of cherry laurel leaves and the compounds emitted therefromupon flexural rigidity of dry archaeological leather from wet burial sites, which uponuncontrolled drying becomes rigid. To aid interpretation or to ease stress and strain on thematerial, it is often desirable to modify the flexural rigidity of the leather to allow for theobject to be reformed. A review of current leather treatments which modify flexural rigidity:immersion, humidity chambers and infusion with humectants followed by freeze drying,indicates that some dry archaeological leathers would not withstand these treatments due toinduced collapse and cross-linking of collagen fibres. Treatment with cherry laurel leaves(Prunus laurocerasus) has been proposed as an alternative method, but there is a general lack ofliterature on the treatment and no explanation of the working mechanism of the treatment.Considering the time and constrained resources, a limited number of methods were selectedto first evaluate the effect of the treatment on dry archaeological leather, and then clarify themechanism of the treatment.An apparatus to measure the flexural rigidity of leather was designed and constructed. Resultsfrom this instrument were used to demonstrate that; a) the treatment depends upon emissionof volatile compounds from the crushed leaves; and that b) benzaldehyde and water are theactive compounds in the treatment. An experiment comparing the effects of a matrix oftreatments: 1) chopped cherry laurel leaves in contact; 2) chopped cherry laurel leaves in noncontact;3) benzaldehyde + distilled water; and, 4) 4-Methoxybenzaldehyde + distilled waterwas conducted by measuring changes in: flexural rigidity, pH, surface colour, weight, length,width, thickness and evaluate other attributes such as visual appearance, touch/texture,workability with respect to both before and immediately after treatment and also with respectto treatment reversibility through elapsed time following treatment. This experiment indicatesthat all treatments work in a similar way, but to different extents, and that the presence of analdehyde + moisture is required for modification of flexural rigidity. Benzaldehyde with waterwas found to be the most effective treatment. The results also indicate that the treatments arereversible within an acceptable time frame with the changes in the above measured propertiesreturning to their original values within 48 hours following treatment. Benzaldehyde withwater has the added benefit of not involving the emission of HCN(hydrogen cyanide), as isthe case when cherry laurel leaves are used, which is both an acute toxin and a potentialhazard for the leather