If you want to change properties of the material, please use at first Updating and at least Updated. These guaranties that only one time an Update-call is fired.

// Sample
Material m = new Material();
m.Updating();
m.Ambient    = Color.Red;
m.Specular    = Color.Blue;
.
.
m.Updated();
// now the virtual method Update will be called

See Also

Material Class | Minais.Drawing3d.Materials Namespace