Műtárgyvédelem, 2009 (Magyar Nemzeti Múzeum)
Kovács Petronella: Zsugorodási hőmérséklet - a bőrök lebomlási fokának értékmérője
Műtárgyvédelem 34 and so the changes could be followed as they were taking place. Within such circumstances, three values could be recorded at every sample: the starting temperature of Larsen’s phase Al, the start of phase C, which is the shrinkage temperature (Ts), and the temperature values at the termination of the shrinkage activity of the fibres. The shrinkage temperature measured on the fibres of the samples taken from vegetable-tanned leather coatings was 43-44 °C in average. Apart from two exceptions, the shrinkage temperature of the examined samples decreased to about the half of the Ts value - 75-85(90) °C - of the new vegetable-tanned leathers and the complete shrinkage of the fibres took place under the minimal shrinkage temperature of new vegetable-tanned leathers. The shrinkage temperature values measured on alum-tanned leather coatings - 35-38 °C - were also much lower than the shrinkage temperature of new alum-tanned leathers - 50-63 °C. The shrinkage temperature (67 °C) of the vegetable-tanned sample taken from the coating of the drawer of one of the chests proved to be the highest. It corroborates that beside the natural aging process of leathers, environmental effects also influence the rate of decomposition since the leather coating of the drawer was less effected by air pollution and other environmental deteriorating factors (light, heat, pollutants of oxidative effects) within the chest. The results of the measurements of the shrinkage temperature refer only to the fibrous components of the samples since the examined fibres were extracted from the reticular layer. The grain layer of the leather covers are probably in an even more decomposed state. It should also be mentioned that the measured values are characteristic of the areas of the leather coverings of the chests from where the samples were taken and although samples from more than one part of the chests were examined, the data should be treated as average values because of the large sizes of the coatings. A szerző cime/Authors'address: Kovács Petronella DLA Fa-bútor restaurátor művész/Wooden object and furniture conservator DLA e-mail: kovacs.petronella@gmail.com 94
