diff --git a/Assets/VRM10_Samples/VRM10Viewer/VRM10VisualPrimitive.cs b/Assets/VRM10_Samples/VRM10Viewer/VRM10VisualPrimitive.cs
index f6bc44257..b87a30f79 100644
--- a/Assets/VRM10_Samples/VRM10Viewer/VRM10VisualPrimitive.cs
+++ b/Assets/VRM10_Samples/VRM10Viewer/VRM10VisualPrimitive.cs
@@ -36,7 +36,10 @@ namespace UniVRM10.VRM10Viewer
             {
                 if (_urpMaterialForGrayscale != null)
                 {
-                    visual.GetComponent<Renderer>().material = Instantiate(_urpMaterialForGrayscale);
+                    var m = Instantiate(_urpMaterialForGrayscale);
+                    m.SetFloat("_Metallic", 0);
+                    m.SetFloat("_Roughness", 1);
+                    visual.GetComponent<Renderer>().material = m;
                 }
             }
         }