A Raman spectroscopic study of glass trade beads excavated at Mapungubwe hill and K2, two archaeological sites in southern Africa,raises questions about the last occupation date of the hill

Thousands of glass trade beads were excavated over a 75 year period on Mapungubwe Hill and at K2, two archaeological sites in the Limpopo valley, South Africa. An assemblage of 175 beads that appeared to be different in shape, size and colour (red, yellow, green, blue, white, black, pink, plum) was studied with Raman scattering. At least seven different chromophores or pigments (lazurite, lead tin yellow type II, Ca/Pb arsenate, chromate, calcium antimonate, Fe–S “amber” and a spinel) have been identified. Pigment identification allows the recognition of specific productions and indicated that many of the pigments colouring the beads excavated on Mapungubwe hill were manufactured after the 13th century, confirming the presence of modern beads in the archaeological record, some dating from the 19th century. This date is in agreement with the last occupation date for the hill suggested by the earlier excavators and raises questions about the revision of this date to 1290 AD by archaeologists in the 1970’s.     

基于明胶微球的新型彩绘文物保护材料的可行性分析与预实验研究

彩绘类文物的彩绘研究和提取保护是考古工作的重点。但彩绘类文物因其自身的脆弱性而难以保存，需要进行一定的修复加固保护。现有加固保护材料由于大多与文物本体材质存在差异，致使加固保护长时间后，会与本体形成开裂，甚至剥离，宏观表现为“保护性破坏”。本研究着眼于使用彩绘类文物中传统的胶结材料，即动物明胶，但因明胶特有的溶胶-凝胶性，难以直接在文物上使用。因此，本研究首次提出将明胶微米化、纳米化，以“先渗透，再交联”的方式，有效回避明胶的溶胶-凝胶性，实现原材料保护修复。实验使用条件温和的乳化交联法，制备出尺寸为2～4μm的明胶微球，使用扫描电镜、红外光谱对其进行表征，并在模拟彩绘样块上进行透气性以及大红染色观察渗透性等的实验，初步证明作为加固剂的明胶微球新材料基本符合文物保护材料的标准要求。在今后更多的实验测试下，明胶微球有望投入使用。