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  1. #1
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    Default Metal bluing solution

    Does anyone know where i could buy this around melbourne?
    Art has now be-come
    Sim-ply an ex-cuse to sit
    In the Sun . What Fun!
    BC-haiku

  2. #2
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    Quote Originally Posted by ohno View Post
    Does anyone know where i could buy this around melbourne?
    You can buy a tube at most auto stores, just don't call it Prussian Blue, the darn fools only recognise it by brand name or 'metal blue'.

  3. #3
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    Quote Originally Posted by Groggy View Post
    You can buy a tube at most auto stores, just don't call it Prussian Blue, the darn fools only recognise it by brand name or 'metal blue'.
    Cheers.
    Art has now be-come
    Sim-ply an ex-cuse to sit
    In the Sun . What Fun!
    BC-haiku

  4. #4
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    Oct 2003
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    Sydney,Australia
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    You really have to be more specific - hot blue, cold blue or marking blue.

    Groggy is talking about marking blue - a greasy stuff you smear on to metal and then press something on to see where it touches - much used in fitting & engine work. Also handy for painting on door handles to find out who has been getting into the locked storage - it is a right B@$^(^d to get off.

    Hot blue is a chemical metal finish - comes as a coarse powder like salt and is made up with water into a super-saturated solution. Very clean ferrous metal is immersed in the boiling salt solution & goes blue-black almost immediately. It is then taken out, placed in a water bath to remove residual salts, then oiled. Hot blue is readily available in 20 litre drums from specialist sellers of metal treatments (Yellow Pages).

    Cold blue is closely related to hot blue, but uses different salts. It is wiped onto very clean ferrous metal and turns it blue-black after a few applications. If you don't work fast enough, it will turn the metal red-brown with a chemically stable rust finish, much loved of antique shotgun collectors. It is the only blueing that can be used where parts are soldered together (like shotgun barrels) - hot blue eats solder, and has been a source of much amusement at the range when someone has had a 'cheap' blue job done on their $20,000 shotgun, and all the bits fall off with the first shot


    Cold blue is pretty much a DIY job these days, you have to get a formula that works & have a chemist (not a pharmacist, although they should know how) make it up for you in about litre lots. Commercial paste cold blues, sold in gun shops for 'touch up' jobs is hopeless - it will make the job a variety of colours from grey thru' black & then turn a sort of muddy dark brown in a few weeks

    Oh, and they are all pretty toxic of ingested, so wear gloves & don't dump any down the drain or the EPA will be after you.

  5. #5
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    Quote Originally Posted by bsrlee View Post
    Groggy is talking about marking blue - a greasy stuff you smear on to metal and then press something on to see where it touches - much used in fitting & engine work.
    I would call that bearing blue.

    Marking blue is painted onto metal like an ink then you mark out over it with a scriber so your lines stand out.
    Dan

  6. #6
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    Dan, that sounds correct - I'm not a trained precision metal worker, more of a get-a-bigger-hammer type who has picked up a bit from friends over the years, and sweated over a few blue tanks too.

  7. #7
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    Seaton, South Australia
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    Hi bsrlee,
    Have wondered what goes into those "cold blueing" solutions that you pay heaps for,like $12+ for a little plastic bottle.I just recently had to blue some lathe parts and used both the paste and the solution, and as you say neither were that impressive. eg. Nothing like a professional job done on a rifle barrel.
    Is there a recipe to make you own? or are the chemicals not available to the public?

    Regards,
    Gary.

  8. #8
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    Armidale NSW
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    Default Phosphoric acid

    I thought (and I could very well be wrong) that the chemical blueing agent uses phosphoric acid. I know that it is used in prepping bare metal prior to painting and it leaves the metal blue.

    Cheers.

    Vernon.

  9. #9
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    Tallahassee FL USA
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    From "Handbook of Chemistry and Physics" 41st ed., 1959, p. 3281:

    "BLUING STEEL AND IRON

    The metal is cleaned with a potassium bichromate-sulfuric acid mixture, then washed with ammonium hydroxide and rubbed dry. Apply ammonium polysulfide until the desired depth of color is obtained, allowing the object to dry after each application and rubbing briskly with soft clean cloth. The result is a deep blue which may be made very nearly black by repeated applications. Rubbing with boiled linseed oil will deepen this color more. The finish thus obtained is very resistant to oxidation."

    BTW, the process of using "marking blue" mentioned by bsrlee is called "blueprinting;" useful for any kind of fitting up. And it doesn't have to be blue. And it doesn't have to be for metal, either; also works for wood. I've even used crayons.

    JG
    Of course truth is stranger than fiction.
    Fiction has to make sense. - Mark Twain

  10. #10
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    kiama
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    I have a bottle of "Super blue" made in the USA which I got from a gun shop a few years ago. The bottle says the material is "Selenium Dioxide"

    You polish the steel to a bright clean surface, apply the blue with a rag or sponge leave for 30 seconds and wash off with water. To get a darker colour repeat till satisfied. I find it goes black easily within 2 coats.

    The last thing I used it on was for a thinner washer I made to allow me to get an extra 4mm for dado blades on my table saw. Not being a paint it didn't add to the thickness of the washer.

  11. #11
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    IIRC my mate used one of the formulas in the book 'Firearms Blueing and Browning' - its been in print for about 70 years :eek: but I'm not sure which formula He had an old chemist/pharmacist make it up for him when he was doing a 'lot' of shotgun finishing, including putting the ribs back on after someone else did a bodgy job, but the chemist died some years ago.

    One 'secret' is to put the metal parts into clean, near boiling water before putting on the blue. As you should be using gloves anyway to keep skin oils off the metal (one source of streaky finishes) you can (just) handle the pieces when you pull them out. The remaining water dries off in a few seconds, and any surface rust that forms is absorbed in the bluing process.

    You use clean 'cotton waste' to wad on the blueing solution - any oil contamination see above.

    I was also worried about the commercial cold blue that contains 'Selenium' in a form that is chemically active - the stuff is both toxic and psyco-active in a bad way in even small quantities.

  12. #12
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    Slightly off centre but...
    When I was working out west the first thing you did with your steel gold pan was make an enormous fire and then bury the pan in the white hot coals and leave it overnight.

    The pan would emerge with a lovely blued surface that prevented all rust over its lifetime. ( a rusty pan = hardwork)

    I don't know the chemistry but it works.

  13. #13
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    Nov 2006
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    Hobart, TAS
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    If you don't mind it being on the black side of blue, www.janekits.com.au sell a cold blackening kit which would supposedly give the common tool finish. Haven't tried it myself but am considering it for a couple of small lathe fixtures. This is the only one I've been able to find in smaller quantities.

    I'd imagine that like plating, etching etc cleanliness is the key otherwise a variable result is likely. The Janekits guys include chemical cleaning so that's a good sign I suppose.

    (Not associated in any way)

  14. #14
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    Jun 2006
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    Default

    right. Thanks for a bit more info guys.
    What i need is a cold bluing solution to use of damascus steel in order to bring out the patterns futher.

    The book i've been refering to has two recipes.

    1
    8 fl oz water
    8 fl oz denatured alcohol
    2 fl oz hydrochloric acid
    2 fl oz of ferric chloride.

    2
    1 gal boiling water
    3 oz sodium thiosulfate
    2 oz lead acetate.
    Art has now be-come
    Sim-ply an ex-cuse to sit
    In the Sun . What Fun!
    BC-haiku

  15. #15
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    Garvoc VIC AUSTRALIA
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    The stuff in recipe 1 is easy enough to get
    I think you can get ferric chloride from Jaycar for making printed circuit boards.
    Regards, Bob Thomas

    www.wombatsawmill.com

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