Blade issue

[kachingchingpow]

10 or so years ago I purchased a knife... a Randall copy by Blackjack. I was recently washing it down in my hunting camper after cleaning a deer. The thermostat on my hot water heater is set to "scald," and unfortunately it looks like I held the blade under the water too long, altering the temper. The blade now has a blueish tone to it in places. The same tone that a bolt gets when it's heated up via a bench grinder.

My thought is that what's done is done, and this knife will never look the same short of re-tempering and buffing. Perhaps a bit too much for a $160 knife. I've thought about taking it to my gunsmith and having him blue the blade. I've cold-blued blades in the past and didn't really like the look. Anyone else have any ideas, or issues with blueing?

[The Reaper]

Trust me, your hot water heater does not posess the ability to produce water hot enough to heat steel sufficiently to change its temper, unless your camper has a nuclear reactor with a pressure vessel.

Sounds more like a chemical reaction to me.

You do realize that bluing is oxidation, right? What kind of additives have you put in your water storage tank?

TR

[Bill Harsey]

Reaper got it.
The best you could do with boiling water at one atmosphere (sea level) is about 212 Degrees F.
There is no hardened tool (knife) steel that I know of that could have it's temper harmed at this temperature.

The general "minimal" tempering temperature for a steel which has already undergone its hardening (austenitizing) heat treat phase is 300 degrees F.

There is no blade I've ever made that would be harmed by 300 degrees F after completion. Handles and fittings would be a seperate issue.

The best I would suggest for your blade is to use steel wool and oil and not mess with cold blueing on a knife intended to cut what will become food unless your diet is seriously deficiant in selenium dioxide.

[DanUCSB]

This is what I love about PS.com. A question is asked; a subject matter expert (or several) is generous enough to reply; everyone else learns something they might not have known before. Good times.

[Ambush Master]

Reaper got it.
The best you could do with boiling water at one atmosphere (sea level) is about 212 Degrees F.
There is no hardened tool (knife) steel that I know of that could have it's temper harmed at this temperature.

The general "minimal" tempering temperature for a steel which has already undergone its hardening (austenitizing) heat treat phase is 300 degrees F.

There is no blade I've ever made that would be harmed by 300 degrees F after completion. Handles and fittings would be a seperate issue.

The best I would suggest for your blade is to use steel wool and oil and not mess with cold blueing on a knife intended to cut what will become food unless your diet is seriously deficiant in selenium dioxide.

Is this Blade A Hershey Bar?!?!?!:D:munchin

[kachingchingpow]

No doubt that you can fill volumes with what I *don't* know about tempering metal. The trailer *does* put out some extremely hot water though, so it wasn't difficult to make this assessment. Not to mention I actually watched it happen with my own eyes as it was under the water. I'm going to try to snap a picture or two and get them on here. Hopefully my camera will capture the damage. I've owned this trailer for quite a few years... and it's never done this to any other blade that I've put under it. I *swear* the blade has that same blueish hue that a piece of steel get's when it's exposed to an extreme heat.

As for water... it's well water. I've never tested the water myself, but sulfur is an occasional problem if the power goes out and we deplete the holding tank. When that happens I'll pickup some sulfur into my heater. Usually evident pretty quickly with the familiar "rotten egg" smell. Quick flush of the heater and it's no longer an issue.

Yeah I'm familiar with blueing. Again, I've cold blued few old "tools" (blades would be a complement), just for the sake of cleaning them up a little. Hot blue would be the route I'd go.

[Bill Harsey]

katchingchingpow,
My take on non-stainless blades is that surface discoloration is not a form of damage but deep rust pitting is. Just use fine steel wool and let the blade go dark. If you abrade the surface, it will just rust deeper again. The oxide you see forming is a form of protection, that darker it gets, the better the protection.

pay careful attention to this: DO NOT BUFF A SHARPENED BLADE! very serious injury can result, this is not theory.

I'm not sure that one can hot blue a knife without complete removal of the handle. This would be like blueing a rifle with the wood stock in place.

You are correct that you see the same color as a heat oxide color but I don't think it's from heat. There are two types of oxides on steel, heat and chemical. Some heat can help speed up the chemical reaction that results in color. Blood sodiums are very good at reacting with non-stainless steels.

For this to have been a heat oxide, the blue colors begin at just over 500 degrees F.
You must have some pretty warm water there.

[kachingchingpow]

Thanks Bill.

The water *is* hot, but it's not boiling & spewing from the spigot or anything. I would think we're talking just below boiling, because *I think* it has a valve that opens at about boiling.

You mentioned "blood sodiums," and that sounds interesting. I did just finish dressing a deer, and the blue hue fades along a line about an inch from the back end of the cutting edge toward the top of the blade at about a 45 degree angle. I'm wondering now if the blood had dried on the blade. It might have been sat down while I removed the straps and loins, then I only noticed the oxidation when I washed it off.

Here's the spec's on the blade if it makes any diff.:

Blade Steel: 1095-Cryo @ 58ZRC (it says carbon steel on the blade)
Blade Thickness: .215 in.

I'll play around with some 4 aught wool tonight.

[cold1]

Some Carbon steels react with acids and turn Blue. Think Old Timer brand cutting oranges, The blade starts turning blue immediately. You make have an acidic condition in your water tank.