Il restauro e la protezione della carta mediante trattamento con gel di Gellano

Traditional wet restoration methods for librarian and archival artifacts - such as cleaning by immersion - present lots of limitations that are primarily due to the uncontrolled release of water to the paper supports. An approach able to provide a more gradual release of water to the supports is needed. Using Gellan gum as gelling agent to optimise the presence of water and minimise the impact on the paper supports during cleaning treatments, this method was developed. The Gellan gum method can be used also for deacidification as well as for reductive bleaching pourposes. Different analyses were carried out to assess the suitability and the effectiveness of cleaning treatments of paper artifacts. Some of these were conducted by water immersion, some others by cellulose ethers contact or by Gellan gum rigid gels contact. In particular, colourimetric analysis was performed to quantify colour modification. Microscopy investigations (including SEM) were employed to observe the structural modification possibly occurred on the paper surface. In order to compare the effectiveness of chemical stabilisation treatments, pH and alkaline reserve measurements were performed. During the experiment, modern paper samples and original artifacts - considered "expendable" - are used. Based on the acquired experience, results on three cases of studies are also presented. Results show that the treatment by contact (Gellan gum) is a viable alternative to traditional methods of restoration in terms of effectiveness and safety. Moreover, Gellan gum gel is manageable, easy to use, inexpensive and respectful of the unique characteristics of the archival and librarian artifacts. Concerning deacification and reductive bleaching, better results were obtained using Gellan gum as carrier for aqueous solutions with calcium propionate and borane terz-butylamine complex. This method provides an increase of pH values comparable to that achieved by immersion. Furthermore, it leaves an appreciable amount of alkaline reserve on the paper support. The result obtained on the three case of studies show the same trend, in terms of color changes.