E. Cobham Brewer 18101897. Dictionary of Phrase and Fable. 1898.
Heat greater than white heat.
There be several degrees of heat in a smiths forge, according to the purpose of their work: (1) a bloud-red heat; (2) a white flame heat; (3) a sparkling or welding heat, used to weld barrs or pieces of iron.Kennett: MS. Lansd., 1033, f. 388.