Hydraulicity is a well-known characteristic of mortars and plasters from the Roman, Late Roman, and Medieval periods, while the use of hydraulic mortars in pre-Columbian Mesoamerica and Central Mexico in particular, has not received equal attention. To address this issue, in this paper, we discuss the problem of hydraulicity and suggest a method to study it in Mesoamerican plasters. To prove the effectiveness of this method, we selected plaster samples from the archaeological site of Teotihuacan (Mexico), the main city of Central Mexico during the Classic period. The characterisation of plaster samples confirmed that, similar to other Teotihuacan plasters, they are made of two layers: the outermost layer (enlucido), composed of a mixture of lime and volcanic glass shards, and the underlying layer locally called firme, consisting of crushed volcanic scoria (tezontle) mixed with a mud-based binder. The compositional characterisation of the plasters confirmed their hydraulicity and the combination of microchemical (energy dispersive spectrometer (EDS) microchemical analysis), microphysical (Vickers microhardness), and petrographic (optical microscopy) measurements demonstrated that it was not the presence of glass shards in the external plaster layer which produced hydraulicity, as we originally thought. Instead, this was due to the reactivity of the tezontle, present in the lower layer.

This suggests that the small thickness of the enlucido layer, in addition to save the amount of lime used, increased its performance, promoting chemical reactions with the tezontle in the contact layer and that the glass shards played another role in the mixture, rather than producing hydraulicity.

水硬性是罗马、罗马晚期和中世纪时期砂浆和灰泥的众所周知的特征，而特别是在前哥伦布时期的中美洲和墨西哥中部，水硬砂浆的使用并未受到同等重视。为了解决这个问题，在本文中，我们讨论了水力问题，并提出了一种在中美洲石膏中研究它的方法。为了证明这种方法的有效性，我们选择了古典时期墨西哥中部主要城市特奥蒂瓦坎（墨西哥）考古遗址的石膏样本。石膏样品的表征证实，与其他特奥蒂瓦坎石膏相似，它们由两层组成：最外层 ( enlucido)，由石灰和火山玻璃碎片的混合物组成，下层当地称为Firme，由压碎的火山渣 ( tezontle ) 与泥基粘合剂混合组成。石膏的成分表征证实了它们的水硬性，微化学（能量色散光谱仪 (EDS) 微化学分析）、微物理（维氏显微硬度）和岩相学（光学显微镜）测量的组合表明，在石膏中不存在玻璃碎片。正如我们最初认为的那样，产生水硬性的外部石膏层。相反，这是由于存在于下层的tezontle的反应性。

这表明透明层的小厚度除了节省石灰用量外，还提高了其性能，促进了与接触层中的 tezontle 的化学反应，并且玻璃碎片在混合物中发挥了另一个作用，而不是产生水力。