The wooden artifacts excavated in Gansu are typical rotted wooden objects,based on the shapes and structures of the wood.The woods used were identified as wood from Picea spp.,Sabina spp.and Abies spp.Based on the shape,structure,and effecting issues the wooden artifacts,it is concluded that after the first fundamental change,when the wood moisture content was well below the fiber saturation point,the artifacts experienced a second fundamental change stage,when wood moisture content was close or slightly higher than the moisture content balance point.The change during the second stage is devastating for the artifacts.The microstructure of the wood was observed by cross-sectional microscopy and by scanning electron microscopy.These results match those of the different decay stages of the objects.A piece of coffin wood excavated with other rotted wood artifacts was selected as a research control subject to measure its chemical compositions,volume,weight,moisture content and mechanical properties.It was found that： more than 50% of the wood fiber had degraded and that the wood had a moisture content of 10.5%.In addition,the wood＇s mechanical properties have declined significantly,with its density being about 60% that of normal density of the wood.It is concluded that： 1） the shape and structural condition of the rotted wood match its condition as observed by the cross-sectional method and SEM;measurement of the material composition,volume,weight and mechanical properties provide solid support for the analytical results;2） the main cause of the shape and structural change of the rotted wood is its wood moisture content,a value that changes with the surrounding environment and reflects the material properties of the rotted wood;3） the fiber saturation and moisture content balance points are very important physical parameters that could affect the shape and structure of the wooden artifact;4） depending on the properties of the rotted wood artifacts,their preservation should be done without direct contact with water.The moisture content of the wood artifacts should be strictly controlled.A stable and constant environment is crucial for the preservation of rotted wood artifacts.%甘肃出土木器依据形态与结构划分,属于典型的糟朽木器类型,材质外观特征与特性明显。制作材质鉴定表明,基本类型有①松科云杉;②松科冷杉;③柏科圆柏。通过对糟朽木器形态类型、结构属性、影响因素及发生改变原因剖析,指出了糟朽木器材质在经历了第一阶段的转折性根本改变后（含水率远低于纤维饱和点）,即将面临第二阶段的转折性根本变化（含水率略高或接近于平衡含水率）,而这一阶段的改变结果对器物将是毁灭性的;为了避免出土器物在短期内形态发生剧变,运用生物切片、扫描电镜分析技术对木质纤维显微结构进行了观察和研究,研究结果与结构病害腐变结果相吻合。选取与糟朽器物同期考古出土的糟朽棺板木作为分析对象,分别对其化学成分、容积重、含水率以及力学性能进行了实验测试,测得糟朽木器降解损失超过50%,含水率约为10.5%,力学强度指标与正常材质相比,均有明显的下降,且相对差异较大,最大约为正常木材强度的60%。对比分析结果,得出了结论：①糟朽木器的形态与结构状况与实验生物切片分析、电镜显微结构观察和研究结果相吻合,同时材质成分、容积重与力学性能测定结果为上述分析结果提供了有力的数据支撑;②致使糟朽木器形态和结构发生改变的主要因素是胎木含水率,其值是非恒定的并随外部环境而改变,因此含水率可用于反映糟朽木器的材质特性;③纤维饱和点与平衡含水率是影响、衡量和评估糟朽木器形态与结构的两个重要的物理参数;④鉴于糟朽木器的材质特性,后期保存应尽量避免与水分的直接接触,需要严格控制其胎木的含水率,且维持恒定、稳定的保存环境,这点对后期糟朽木器的保存是非常重要的。
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