A scrapped shell had two "product castings" snapped off the the runner system and sectioned. Both were identical - one is shown in the pictures.
The holes from the snapping-off were sealed with fireclay - so the amount of atmosphere access was identical to as if the shell were unaltered - and the dewaxed shell was fired in the gas-fired rotary hearth furnace at 1050C for around 2 hours as if it were a regular shell going to be poured. But it was removed from the furnace at unloading time and allowed to go cold. Then another two "product castings" were snapped off the runner system and sectioned. Parts of both can be seen in the photos.