A piezometric relationship is derived between subgrain size and stress in plastically deformed crystalline materials, based on the assumption that subgrain boundaries become stabilized once their strain energy per unit area exceeds that in the adjacent lattice. The subgrain diameter at this point depends on the density of geometrically necessary dislocations (GND), many of which are housed in the subgrain walls, and on their spacing in the walls. Subgrains grow by merging, which results in a linear relationship between size and misorientation. The piezometric relationship for any given misorientation has a stress exponent close to unity. The subgrain piezometer can be calibrated using literature-based estimates of the size of dynamically recrystallized grains produced by subgrain rotation (SGR) for different minerals.

Grain-size piezometers reflect processes of nucleation and post-nucleation modification during dynamic recrystallization. New grains formed by these different processes occupy different regions in grain-size/stress space. These regions are bounded by the subgrain piezometer and the Dmin line, which marks the smallest size that newly formed grains can have without being eliminated by surface-energy driven grain-boundary migration. The piezometers are statistically defined by the scatter of grain-sizes produced by these different processes. Piezometers defined in this way for quartz, olivine, and calcite correspond well within uncertainties to experimentally determined piezometers. No experimental piezometer exists for feldspars; a piezometer based on the concepts advanced in this paper is suggested that can be tested by experiment.

基于这样的假设，一旦单位面积的应变能超过相邻晶格的应变能，亚晶界就会变得稳定，从而得出塑性变形晶体材料中的亚晶尺寸和应力之间的压压关系。此时的亚晶直径取决于几何必要位错 (GND) 的密度（其中许多位错位于亚晶壁中）以及它们在壁中的间距。亚晶粒通过合并而生长，从而导致尺寸和取向错误之间存在线性关系。任何给定的错误取向的测压关系具有接近于1的应力指数。亚晶渗压计可以使用基于文献的对不同矿物的亚晶旋转 (SGR) 产生的动态再结晶晶粒尺寸的估计来校准。

晶粒压力计反映了动态再结晶过程中的成核和成核后改性过程。由这些不同过程形成的新晶粒占据晶粒尺寸/应力空间中的不同区域。这些区域以亚晶压力计和 Dmin 线为界，Dmin 线标志着新形成的晶粒在不被表面能驱动的晶界迁移消除的情况下可以具有的最小尺寸。压力计是通过这些不同过程产生的颗粒尺寸的分散性来统计定义的。以这种方式定义的石英、橄榄石和方解石的渗压计在不确定性范围内与实验确定的渗压计很好地对应。不存在针对长石的实验压力计；建议使用基于本文先进概念的压力计，可以通过实验进行测试。