ABSTRACT

In the preservation of cultural heritage, the measurement of pH has implications both as a parameter for assessing the state of conservation and as a reference for the preparation and use of aqueous treatment solutions. Few studies in the relevant literature, however, deal with evaluating the reliability of measurements. The purpose of this study was to identify the best method and the confidence limits for measurements of surface pH on linen canvas. The results obtained with the two main methods currently used, water drop and rigid gel, were evaluated and compared with warm extraction. Agarose at different concentrations was used for preparing rigid gels, and the influence of the volume of the gel was also evaluated in the latter measurements. Five canvas samples with different degree of acidity were tested: highly acidic, acidic, weakly acidic, a new linen canvas, and the lining canvas recovered from a painting dating around the middle of nineteenth century. The theoretical surface pH values (pH_st), derived from the measurements obtained by the aqueous extraction method, were used as standards against which to assess the reliability of the measurements.

摘要

在文化遗产的保护中，pH 值的测量既可以作为评估保护状态的参数，也可以作为制备和使用水性处理溶液的参考。然而，相关文献中很少有研究涉及评估测量的可靠性。本研究的目的是确定测量亚麻帆布表面 pH 值的最佳方法和置信限。对目前使用的两种主要方法（水滴和硬凝胶）获得的结果进行了评估，并与温提取进行了比较。不同浓度的琼脂糖用于制备刚性凝胶，凝胶体积的影响也在后面的测量中进行了评估。测试了五种不同酸度的帆布样品：强酸性、酸性、弱酸性、一块新的亚麻帆布，内衬帆布是从 19 世纪中叶左右的一幅画中恢复的。理论表面 pH 值 (pH_st )，从通过水萃取法获得的测量值得出，被用作评估测量值可靠性的标准。