The mystery of the burning cage, in which the Fire King remains while a steak is thoroughly cooked, is explained by Barnello as follows:
"Have a large iron cage constructed about 4 x 6 feet, the bottom made of heavy sheet iron. The cage should stand on iron legs or horses. Wrap each of the bars of the cage with cotton batting saturated with oil. Now take a raw beefsteak in your hand and enter the cage, which is now set on fire. Remain in the cage until the fire has burned out, then issue from the cage with the steak burned to a crisp.
Explanation: On entering the cage the performer places the steak on a large iron hook which is fastened in one of the upper corners. The dress worn is of asbestos cloth with a hood that completely covers the head and neck. There is a small hole over the mouth through which he breathes.
As soon as the fire starts the smoke and flames completely hide the performer from the spectators, and he immediately lies down on the bottom of the cage, placing the mouth over one of the small air holes in the floor of the same.
Heat always goes up and will soon cook the steak."
I deduce from the above that the performer arises and recovers the steak when the fire slackens but while there is still sufficient flame and smoke to mask his action.
Piece of cake! Er, steak!