I've always maintained that you should never get a knife blade hotter than you can "touch". I know many knife "sharpeners" maintain that theory, siting the fact that they do not have to worry about ruining the temper, heat-treat, rockwell, etc. I think a "Kettle" may be going a bit too hot. If I can clean a blade with a "warm/hot" to the touch temperature I think (for me anyway) that this is hot enough. Perhaps someone else has another idea??
Best, Capt. Chris