Blueing dangerous !?

[Erka]

Hello,
as I am new in this forum, let me say first hello to you guys. I just started this summer with knife-making, and do enjoy it alot.
After reading the very good thread 'Safety concerns for new knifemakers' I thought this is the right forum for this:
I thought about blueing a carbon steel blade, for some corrosion protection and for the nice dark look of it. I have some Perma-Blue and Super-Blue solution of Birchwood-Casey, which is sold for repairing the blued surface of guns. Maybe that was a bad idea anyway, and most of you would not think about doing that. But then, a lot of the people here will probaly have one or more guns too, so I hope this could be of interest anyway.
Remembering all the safety warnings on these bottles for the aplication (poisonous, risk of cancer...), I was wondering how 'healthy' such a bluead surface may be. So, before putting this stuff on a blade which might also be used to cut some food, I decided to ask them if there could be a health risk. So I tried to get in contact with Birchwood Casey, using the contact form on their website and then, because nothing happened, sending an email (which I know was received, because I got a notification). After 3 weeks an no answer at all, I sent a fax with my concerns to Birchwood Laboratories, because a fax usualy cannot be lost as easily as an email. Again no answer (this was 10 days ago). I cannot believe in such a bad customer service, and I take no answer for an answer: Does it seem to be fair to assume that they did not respond, because they would have to admit that even a blued coating can be harmful, at least when applied to a blade in contact with food? I think so.
Anyway, I do not want to use these blueing products on a knife, and personally I will not use them any more on anything that I touch with my hands. Of course everybody gets daily in contact with dozens of more or less harmful chemicals, but in this case I can easily avoid ist.
I guess that industrial blueings may be different, AFAIK these products ar applied under heat, and probably are more safe.
Any comments or ideas about that?

Erka

 

[Matt Shade]

The process you're talking about is cold bluing. If you're careful in how you handle the chemicals while you are applying it, it won't hurt you. After the fact, the knife is every bit as safe and clean as a non blued one.
The blue color comes from etching the steel. Its controlled oxidation, and when you are done, and have neutralized the chemicals, the piece is every bit as safe to handle as a normal knife. The chemicals don't stay on it, its not like paint.

 

[Erka]

Thanks for the fast reply, Matt.
I just thought that this cold blueing is very different than the 'real' blueing process.
The few sources I found stated that cold blueing '...is not a lasting ferric oxydule skin, but just the iron stained with selenium acid'. That's why I am afraid that some of the selenium (and maybe other stuff) still is in the surface. And what really made me somewhat nervous was the strange behaviour of tis company. Offering a special form to get in contact with them, and then not answering does not seem very logical...
Anyway, if the number of your posts does correspond just a little bit with your experience and your knowledge - and thats what I guess, it's probably safe to use

Erka

 

[STR]

Its best to wear gloves. Selenium dioxide is absorbed through the skin. Just small trace amounts can be handled by the kidneys but the fact is it accumulates over time and can cause kidney damage or even failure if you do it too much or absorb too muchnin your system so I would highly recommend rubber latex gloves if you are doing it a lot. I wear my respirator also because I can't stand the smell of it. It can cause asthma symtoms if you are prone to that kind of thing.

 

[suthincomfort]

use 44/40 by brownells i have found it works well when i'm even doing damascus because it darkens all but the nickel on the blade on carbon knives it's give s a good even blue easier to control cya

 

[howiesatwork]

44/40 is a great cold blue.
If you want a more lasting bluing, then you'll need to hot blue it.
A gunsmith can do it for you, as settting up for hot bluing can get expensive and dangerous...

 

[Erka]

Funny, I just received an answer from Birchwood Casey (and an apology for the delay), which I want to share with you.
They 'recommend that knife blades treated with Perma Blue or Super Blue may not be used for preparing food. Blades treated with Perma Blue or
Super Blue contain small amounts of chemical that could contaminate the
food.'

I assume that this will be more or less the same with all cold blueing solutions.
Cutting an apple from time to time with such a blued knive probably would not be a risk at all, but I would not use it frequently - and I will certainly not cold blue a kitchen knife.

 

[ysforge]

For a permanent blue, get it hot blued, it's not terribly expensive to get done if you have it prepared, and as long as it's the "low temp" stuff, blueing takes place at bellow the tempering tempratures, so shouldn't harm useability.