diff --git a/gprMax/cmds_multiuse.py b/gprMax/cmds_multiuse.py
index 27a2252b..56ea5754 100644
--- a/gprMax/cmds_multiuse.py
+++ b/gprMax/cmds_multiuse.py
@@ -1572,7 +1572,7 @@ class SoilPeplinski(UserObjectMulti):
         self.order = 14
         self.hash = "#soil_peplinski"
 
-    def build(self, grid, uip):
+    def build(self, model, uip):
         try:
             sand_fraction = self.kwargs["sand_fraction"]
             clay_fraction = self.kwargs["clay_fraction"]
@@ -1615,7 +1615,7 @@ class SoilPeplinski(UserObjectMulti):
                 "fraction."
             )
             raise ValueError
-        if any(x.ID == ID for x in grid.mixingmodels):
+        if any(x.ID == ID for x in model.mixingmodels):
             logger.exception(f"{self.params_str()} with ID {ID} already exists")
             raise ValueError
 
@@ -1631,14 +1631,14 @@ class SoilPeplinski(UserObjectMulti):
         )
 
         logger.info(
-            f"{self.grid_name(grid)}Mixing model (Peplinski) used to "
+            f"{self.model_name(model)}Mixing model (Peplinski) used to "
             f"create {s.ID} with sand fraction {s.S:g}, clay fraction "
             f"{s.C:g}, bulk density {s.rb:g}g/cm3, sand particle "
             f"density {s.rs:g}g/cm3, and water volumetric fraction "
             f"{s.mu[0]:g} to {s.mu[1]:g} created."
         )
 
-        grid.mixingmodels.append(s)
+        model.mixingmodels.append(s)
 
 
 class MaterialRange(UserObjectMulti):
diff --git a/gprMax/grid/fdtd_grid.py b/gprMax/grid/fdtd_grid.py
index ec6bb363..6084f33b 100644
--- a/gprMax/grid/fdtd_grid.py
+++ b/gprMax/grid/fdtd_grid.py
@@ -32,7 +32,7 @@ from gprMax import config
 from gprMax.cython.yee_cell_build import build_electric_components, build_magnetic_components
 
 # from gprMax.geometry_outputs import GeometryObjects, GeometryView
-from gprMax.materials import Material, process_materials
+from gprMax.materials import process_materials
 from gprMax.pml import CFS, PML, build_pml, print_pml_info
 from gprMax.receivers import Rx
 from gprMax.snapshots import Snapshot
@@ -76,7 +76,6 @@ class FDTDGrid:
         # TODO: Add type information.
         # Currently importing GeometryObjects, GeometryView, and
         # SubGridBaseGrid cause cyclic dependencies
-        self.mixingmodels = []
         self.averagevolumeobjects = True
         self.fractalvolumes = []
         self.geometryviews = []
diff --git a/gprMax/model.py b/gprMax/model.py
index 0edc4e52..df379b37 100644
--- a/gprMax/model.py
+++ b/gprMax/model.py
@@ -28,7 +28,7 @@ from colorama import Fore, Style, init
 
 from gprMax.grid.cuda_grid import CUDAGrid
 from gprMax.grid.opencl_grid import OpenCLGrid
-from gprMax.materials import Material
+from gprMax.materials import Material, PeplinskiSoil
 from gprMax.subgrids.grid import SubGridBaseGrid
 
 init()
@@ -66,6 +66,7 @@ class Model:
         self.G = self._create_grid()
         self.subgrids: List[SubGridBaseGrid] = []
         self.materials: List[Material] = []
+        self.mixingmodels: List[PeplinskiSoil] = []
 
         # Monitor memory usage
         self.p = None