diff --git a/src/experimental/_impl/_sf_square_surfaces.scad b/src/experimental/_impl/_sf_square_surfaces.scad
new file mode 100644
index 00000000..82294dc4
--- /dev/null
+++ b/src/experimental/_impl/_sf_square_surfaces.scad
@@ -0,0 +1,21 @@
+function _sf_square_surfaces(levels, thickness, invert) =
+    let(
+        rows = len(levels),
+        columns = len(levels[0]),
+        surface1 = [
+            for(r = [0:rows - 1]) 
+            [
+                for(c = [0:columns - 1]) 
+                let(lv = invert ? 255 - levels[rows - r - 1][c] : levels[rows - r - 1][c])
+                [c, r, lv / 255 * thickness]
+            ]
+        ],
+        surface2 = [
+            for(r = [0:rows - 1]) 
+            [
+                for(c = [0:columns - 1]) 
+                [c, r, 0]
+            ]
+        ]        
+    )
+    [surface1, surface2];
diff --git a/src/experimental/sf_square.scad b/src/experimental/sf_square.scad
index ce12358b..7ba0c2c5 100644
--- a/src/experimental/sf_square.scad
+++ b/src/experimental/sf_square.scad
@@ -1,4 +1,4 @@
-use <experimental/_impl/sf_solidify.scad>;
+use <experimental/_impl/_sf_square_surfaces.scad>;
 use <experimental/sf_solidify.scad>;
 
 /*
@@ -7,26 +7,17 @@ use <experimental/sf_solidify.scad>;
     invert: inverts how the gray levels are translated into height values.
 */
 module sf_square(levels, thickness, invert = false) {
-    rows = len(levels);
-    columns = len(levels[0]);
+    surface = _sf_square_surfaces(levels, thickness, invert);
     offset_z = invert ? thickness : 0;
-    size = [columns - 1, rows - 1];
-
+    
     sf_solidify(
         [
-            for(r = [0:rows - 1]) 
+            for(row = surface[0]) 
             [
-                for(c = [0:columns - 1]) 
-                let(lv = invert ? 255 - levels[rows - r - 1][c] : levels[rows - r - 1][c])
-                [c, r, lv / 255 * thickness + offset_z]
+                for(p = row) 
+                    p + [0, 0, offset_z]
             ]
         ],
-        [
-            for(r = [0:rows - 1]) 
-            [
-                for(c = [0:columns - 1]) 
-                [c, r, 0]
-            ]
-        ]     
+        surface[1]
     );
 }
\ No newline at end of file