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As every range was a cast-iron, it was kept clean with a polish called 'black lead' which was specially for cleaning and shining cast iron. It came in a tin with the picture of a Zebra on.
My mother's written recollections make it clear that the outer rims of the range in her home were steel and kept bright with emery paper.
I understand that, more generally, the insides of the ovens were kept clean by heating them to a high temperature and burning off the soot. Some insides of ovens may have been removable for cleaning purposes.
As an older child it was one of my daily jobs to 'black-lead' the kitchen range, once I had cleared out ashes and relayed the fire. Then I had to polish up the exposed metal with wire wool.