This is an Aga. Years of fat and oil has been oxidised all over the
enamel and chrome parts on the top to make a solid coating. In cooler
places it's soft, very hard where it has been hotter and burned right
off only on the very hot places like the hot plates themselves. How do I
clean it off?

So far tried various 'dissolves grease' cleaning products and green
scourers. Doesn't really work. A blunt table knife seems to remove the
stuff without scratching the enamel too badly but it's very laborious.
Is there a chemical solution? Even to soften it up?

TW