Is it okay to kiln wash the underside of a kiln shelf?

We recommend kiln washing only the top of the shelf for ceramic firings. Kiln wash applied to the underside of the shelf can flake off and land on glazed ware underneath. However, for a glass kiln with only one shelf, it would be okay to kiln wash both sides of the shelf provided the kiln does not have elements in the floor of the kiln.