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Bryan W.





Joined: 27 Oct 2007

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PostPosted: Fri 20 Mar, 2009 2:16 pm    Post subject: Bluing and steel questions         Reply with quote

Kind of a silly question but I was reading more about the different types of bluing processes since I'm fairly ignorant regarding them. If I'm reading this correctly, it seems many of these (if not all) are acidic and corrosive which is how they get the color, but does this have any noticeable effect on an expensive, high carbon steel blade after a time (ie: cause increased pitting, weakening the steel, etc)?

Also is there substances out there to touch up scratched bluing or is it better to have someone (or yourself) polish it all down and do it again from scratch?

EDIT: Nevermind. Search functions help. I couldn't find an explicit answer but from the information I think I can imply one Happy
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Lin Robinson




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PostPosted: Fri 20 Mar, 2009 5:47 pm    Post subject: Re: Bluing and steel questions         Reply with quote

Bryan W. wrote:
Kind of a silly question but I was reading more about the different types of bluing processes since I'm fairly ignorant regarding them. If I'm reading this correctly, it seems many of these (if not all) are acidic and corrosive which is how they get the color, but does this have any noticeable effect on an expensive, high carbon steel blade after a time (ie: cause increased pitting, weakening the steel, etc)?

Also is there substances out there to touch up scratched bluing or is it better to have someone (or yourself) polish it all down and do it again from scratch?

EDIT: Nevermind. Search functions help. I couldn't find an explicit answer but from the information I think I can imply one Happy


1. No...Bluing and browning are controlled rusting processes, and put a protective finish on the steel. As rusting processes they have to be stopped when the desired finish is reached. There are a number of ways this is accomplished, depending on what solution and techniques are being used. But once the process is stopped, no further chemical reaction occurs with the steel, if it is done correctly.

2. There are some products which can be used to touch up damaged bluing but I have never used one that worked to my satisfaction.

Lin Robinson

"The best thing in life is to crush your enemies, see them driven before you and hear the lamentation of their women." Conan the Barbarian, 1982
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Bryan W.





Joined: 27 Oct 2007

Posts: 198

PostPosted: Fri 20 Mar, 2009 6:05 pm    Post subject:         Reply with quote

Thanks Lin. One of the threads I was reading under the search function here mentioned that hot bluing can affect the temper of the blade if used on it. Is this true?
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Lin Robinson




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PostPosted: Sat 21 Mar, 2009 12:57 pm    Post subject:         Reply with quote

Bryan W. wrote:
Thanks Lin. One of the threads I was reading under the search function here mentioned that hot bluing can affect the temper of the blade if used on it. Is this true?


Bryan...

As far as I know, hot bluing does not involve heat much greater than the boiling point of water. But, I have never done any bluing of any kind myself, although I have browned a number of muzzle loading gun barrels, so I cannot say that for sure. When rust bluing first became popular among gun makers, it involved immersing the piece to be blued in boiling water. So, I cannot say for sure, but I don't think that you have to heat the metal enough to affect temper. There is probably someone out there who knows more about this than I do and who will respond to your question.

Lin Robinson

"The best thing in life is to crush your enemies, see them driven before you and hear the lamentation of their women." Conan the Barbarian, 1982
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Jared Smith




Location: Tennessee
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PostPosted: Sat 21 Mar, 2009 1:14 pm    Post subject:         Reply with quote

Lin Robinson wrote:

As far as I know, hot bluing does not involve heat much greater than the boiling point of water.


(You are basically correct given the wide range of heat treat, tempering and blacksmithing temperatures.) Most of the blacksmith recipes call for about 275 F to 300F. 2/3 Lye and 1/3 potasium nitrate-salt peter have to be dissolved in roughly an equal weight of water, gradually. In principle it is simple, but in practice boiling acid can geyser and eat through clothing, flesh, etc. If done well (30 minute soak), it can be fairly deep and durable as a finish. I have dreams of treating a hauberk this way.

Absence of evidence is not necessarily evidence of absence!
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Michal Plezia
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PostPosted: Sun 22 Mar, 2009 5:33 am    Post subject:         Reply with quote

Do you know what kind of lye?
www.elchon.com

Polish Guild of Knifemakers

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it that is the only truth.
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Jared Smith




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PostPosted: Sun 22 Mar, 2009 8:18 am    Post subject:         Reply with quote

You have several options. Sodium hydroxide is what you want from the lye. Fairly clean grades of it are readily available as soap making supplies. It costs something like $2 U.S. per lb. I would recommend a seamless vessel (like a 300 series stainless stock pot and turkey fryer on low heat, improvised splash guard. Homebrewers usually have this. I have two 10 gallon vessels myself. The stainless should hold up to potassium nitrate and sodium hydroxide. More elaborate bluing recipes may ruin the passivation of the stainless though.) One should note that the batch starts off with water. Lye is added to water, NOT water added to lye (boom!)
The blade makers and gun forums usually have common fertilizer and household cleaning type substitutes.
http://castboolits.gunloads.com/archive/index.php/t-36054.html

http://www.geocities.com/kemays/formula.htm

Absence of evidence is not necessarily evidence of absence!
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