Clayton M. Posted August 24, 2014 Share Posted August 24, 2014 I tempered my first knife a day ago at about 400 degrees( my toaster oven only goes by hundreds of degrees). I put it in the oven and left it there for two hours. When i pulled it out it came out looking like a rainbow.What did i do wrong? I've spent some time thinking about it and i've come up with a few ideas as to why that happened. I put the knife in the oven diagonally because that was the only way it would fit, the middle of the knife turned blue right where that knife rested, above the heating element, on the rack.The blue is interrupted by a bronze strip exactly where the knife rested above the heating element. The reason i'm wondering what happened is because i thought at 400 degrees the whole knife would take on a straw color not any other color let alone a rainbow of most of the oxidation colors. Can anyone help me understand what happened? Should i continue with another tempering cycle, or should i start over and re-harden the blade and try again? Quote Link to comment Share on other sites More sharing options...
KRS Posted August 24, 2014 Share Posted August 24, 2014 Place it further away or shield of the radiation heat. The element heats on full power until the ambiance sensor turns off. Quote Link to comment Share on other sites More sharing options...
Steve Sells Posted August 24, 2014 Share Posted August 24, 2014 lay down a heat sheild to deflect direct heat Quote Link to comment Share on other sites More sharing options...
jmccustomknives Posted August 24, 2014 Share Posted August 24, 2014 I've found that any oils on the blade left from quenching will cause the colors to be off. Clean the oil of. I also use one of those cookie sheets that are doubled to keep from burning the bottoms. It helps. Quote Link to comment Share on other sites More sharing options...
Clayton M. Posted August 24, 2014 Author Share Posted August 24, 2014 Do i need to re-harden it before trying again or can i just do another cycle? I would assume i have to re-harden the knife. Quote Link to comment Share on other sites More sharing options...
EricJergensen Posted August 25, 2014 Share Posted August 25, 2014 Yup. Looks like you've probably drawn too much temper. You'll have to re-harden. Quote Link to comment Share on other sites More sharing options...
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