Blueing a Blade

Gliden07

Well-Known Member
#1
I have a question. I've seen some blade makers after hardening and tempering take a torch to the blade to get that Blued hue to it. Doesn't that mess up the heat treat??
 

C Craft

Well-Known Member
#2
My first thought was you were speaking of case hardening. While it may look OK it is no good for a knife!
https://en.wikipedia.org/wiki/Case-hardening

I think what you are speaking of is something like this! http://www.instructables.com/id/How-to-colour-steel-with-HEAT/

From the link above they are using a pen torch which I doubt that would get hot enough to ruin a HT. Grant you though I have not read through the entire article, nor have I done it myself. Some others may have more info to contribute!!

There are other processes, that I have heard of might be too hot to not hurt the HT on the knife!! Hope that helps.
 
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Gliden07

Well-Known Member
#3
My first thought was you were speaking of case hardening. While it may look OK it is no good for a knife!
https://en.wikipedia.org/wiki/Case-hardening

I think what you are speaking of is something like this! http://www.instructables.com/id/How-to-colour-steel-with-HEAT/

From the link above they are using a pen torch which I doubt that would get hot enough to ruin a HT. Grant you though I have not read through the entire article, nor have I done it myself. Some others may have more info to contribute!!

There are other processes, that I have heard of might be too hot to not hurt the HT on the knife!! Hope that helps.[/QUOTE

I read the article but I don't think this will work third paragraph down reads...

-metal object/s (I used mild steel, Please note this method should NOT be used on tempered/hardened steel as you will effect the properties of the metal.

This is what I thought might be the case?
 

Gliden07

Well-Known Member
#5
No you got the right idea. I remember tempering with my Blacksmith friend and laying it in the cold forge on a big piece of cast and watching the color run til we got that straw color.
 
#6
Basically anytime you change the color of the steel after its hardened using heat you have changed the steel’s hardness. That is the blacksmith’s method of tempering the steel. So if you are finish grinding and get the tip too hot it will change color (we have all done this) that means you have changed the tip’s temper. If I fully hardened a blade (spine and all) I may use a torch to draw some of that hardness back by turning it blue but I would not let that color run to the cutting edge because it would soften it too much. I have seen smiths use a torch to color steel as a finish but always on decorative items not blades. I cannot answer on ruining the blade because that is a relative term but I can tell you color change due to heat=soften
 

Gliden07

Well-Known Member
#7
Basically anytime you change the color of the steel after its hardened using heat you have changed the steel’s hardness. That is the blacksmith’s method of tempering the steel. So if you are finish grinding and get the tip too hot it will change color (we have all done this) that means you have changed the tip’s temper. If I fully hardened a blade (spine and all) I may use a torch to draw some of that hardness back by turning it blue but I would not let that color run to the cutting edge because it would soften it too much. I have seen smiths use a torch to color steel as a finish but always on decorative items not blades. I cannot answer on ruining the blade because that is a relative term but I can tell you color change due to heat=soften
I thought this would be the case but I have seen Bladesmiths do it. On certain knives I thought it would be a cool finish to try, but not at the expense of the HT.
 
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#8
In truth, the only times I have used a torch to temper steel is when I have used it to make a spring for a folder and I took the spring all the way to blue. At blue it was flexible enough to make a good spring. I do not think I would take a cutting edge to blue thats just my opinion. But, there are variables such as the type of steel that makes a difference.
 
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