Page 1 of 2 12 LastLast
Results 1 to 15 of 30

Thread: Darkening cast iron?

  1. #1
    Join Date
    Feb 2004
    Location
    Perth, Australia
    Posts
    9,467

    Darkening cast iron?

    Can anyone recommend an easy way to darken new silvery cast iron (handles). Ideally, I'd like them very dark grey to charcoal or black.


    Regards from Perth


    Derek

  2. #2
    Join Date
    Feb 2004
    Location
    Perth, Australia
    Posts
    9,467

    Darkening cast iron?

    Can anyone recommend an easy way to darken new silvery cast iron (handles). Ideally, I'd like them very dark grey to charcoal or black.


    Regards from Perth


    Derek

  3. #3
    Join Date
    Jul 2013
    Posts
    547
    Blog Entries
    1
    Stove polish. Or cold blue?

  4. #4
    Join Date
    Aug 2007
    Location
    Dickinson, Texas
    Posts
    7,655
    Blog Entries
    1
    I wonder if the cast iron would darken if heated with a torch?

  5. #5
    its just a thought. what about that "bluing" liquid thats used on weapons ? it does not turn blue, but black. I don´t know how it will react with cast iron, but on soft steel it turns black almost instant
    Best regards

    Lasse Hilbrandt

  6. #6
    Join Date
    Jun 2010
    Location
    twomiles from the "peak of Ohio
    Posts
    12,120
    Disston was very good at heating things up a bit, then coating with mineral Oil....to get the backs of the backsaws blued....

    When I rehabbed that spokeshave I accidentally had tossed into the fire pit....I had it down to bare metal....I used Gun Blue Paste...instead of black paint.
    front view.jpg
    Just wipe on, allow to dry, wipe off the excess...
    logo.jpg
    It will also bring out any logos...

  7. #7
    Join Date
    Sep 2015
    Location
    Clayton, WI
    Posts
    193
    Not sure about cast iron, but I do that with steel. Heat it up and then put BLO on it while still hot. Turns it a nice dark gray.

  8. #8
    Join Date
    Jan 2016
    Location
    Longmont, CO
    Posts
    810
    if you want to keep it raw and keep it from rusting, I would suggest seasoning them with unrefined linseed oil, and if they are food grade, unrefined flax seed oil. clean with something strong to remove all residue, use a rag and rub on a light coat of oil, put in cold oven and set for 500 for an hour after it gets to temperature. after the hour, let it cool and repeat. I do 4 or 5 cycles on raw cast and when re seasoning my pans I do a couple coats after a vigorous scrubbing with chain-mail scrubbie and salt. it should turn out a beautiful matte black.

    flax and linseed are the same thing. one is generally processed on food grade equipment and the other is not. very low smoke point so the oil will polymerize. refined oil has a much higher smoke point.

  9. #9
    Interestingly, this is one of the undesirable side-effects of soaking in citric acid -- a technique many use for rust removal.
    It imparts a dull-to-dark grey tone, depending on the soak time.
    My understanding is that Evaporust* has the same side-effect.

    Another option, if you can find it, is "Stove Polish" or "Stove Blacking"


    *don't know if you have this at your location
    Last edited by Joe Bailey; 07-10-2018 at 12:44 PM.

  10. #10
    Leave a leaky cup of coffee on it!

  11. #11
    Join Date
    Apr 2013
    Location
    Stone Mountain, GA
    Posts
    751
    IF the part is fairly small then rust blueing works well and should be more durable than cold blue. You clean and degrease the part, apply the rust blueing solution, wait a few hours for it to rust, then boil it in water for 10 minutes or so to convert red rust to black. Then you wire brush it to remove anything loose, and repeat the process if you want it darker. 3 rounds usually is enough for what I do. I've done a lot of chisels and plane irons, but also a cast iron lever cap, which darkened nicely.

    Another method that blacksmiths use is to heat the part in a forge or with a torch and apply oil. Basically like seasoning a cast iron skillet. Might not be the best feel for a handle though, could be a little sticky.

  12. #12
    Seasoning a cast iron skillet is what I would recommend, Google 'jeffrey rodgers culinary fanatic' to find the guy that does it best. Properly seasoned cast iron will resist rusting and will not be sticky.

  13. #13
    Join Date
    Oct 2014
    Location
    Poughkeepsie, NY
    Posts
    207
    If you want to experiment, I have used this process twice. It is more or less based on a rust conversion and cast iron cookware preparation.

    Oh, and a link to Jeff Rogers seasoning (a little different then what I do)
    http://theculinaryfanatic.com/cast-i...soning-method/

    Step 1: Clean

    -Wash with soap and water to remove any residual oil and other contaminants.
    -Rinse well with water.
    -Dry in a 200ºF oven for 5 to 15 minutes.

    Step 2: Etch

    -Soak in distilled white vinegar for 1 to 4 hours.
    -Rinse well with water.
    -Dry in a 200ºF oven for 5 to 15 minutes.

    Step 3: Patina (rust conversion)

    -Heat some Tannin Tea* to boiling (microwave) and brush it on.
    -Dry in a 200ºF oven for 5 to 15 minutes.
    -Rinse well with water.
    -Dry in a 200ºF oven for 5 to 15 minutes.

    -Repeat around 3 times (when the patina looks good).

    *Tannin Tea recipe:

    Brew a strong cup of tea using 5 to 6 (real) tea bags.
    Optionally add a teaspoon of instant coffee, if you have it.
    Optionally add a teaspoon of wine tannin, if you have it.

    Step 4: Season (coat)

    -Wipe on vegetable oil (flaxseed and linseed oil works if you have it).
    -Wipe off the oil with a dry cloth (this leaves a thin coating).
    -Position your piece(s) in the oven so that if they drip, the blob formed on the piece will be in an unobtrusive area.
    -Put aluminum foil on the bottom of the oven to catch any drips.
    -Bake in 350ºF to 400ºF for 1 hour.
    -Turn off the oven and let cool for 1+ hour.
    -If the seasoning is sticky, bake again at 400ºF.

    -Repeat 1 to 3 times (when it looks good).

    Note: If you have a self-cleaning oven, you can use it to ash (remove) the seasoning.

  14. #14
    Join Date
    Jun 2010
    Location
    twomiles from the "peak of Ohio
    Posts
    12,120
    "Wipe on, wipe off."
    IMAG0240.jpg
    What I use to bring out an etch.

  15. #15
    Join Date
    Jul 2017
    Location
    Calgary AB
    Posts
    179
    https://mypeculiarnature.blogspot.co...-in-black.html
    I came across this method a while back and have found it to create a durable black finish like that of of Japanese tool with its Kuro skin; forge finish. The blog is worth a read too, a favourite of mine.

    This is similar to John's method.

    I have experimented with it a lot a while ago and came up with some variations on the rust solution which fail my memory. I will try looking for any notes I've written. They were particularly quick acting, I dropped a kanna blade in and 30 seconds later there was bubbling rust and the solution was a rich rust colour in 2 minutes.

    Here is an axe which I did this process on for a couple days. I found that a boiling pot of water was better than a steamer and the only option for something this sized. I let it boil for hours at a time.

    IMG_0011.jpg
    ​here it is in its original sorry shape.

    IMG_2416.jpg

    A little less sorry looking now.

    The axe only had some oil and rust removed before I started rusting it, I didn't care about sanding every pit and crevasse away. Or any sort of sanding. A bbq brush and some soap was basically the prep. Turned out okay.

    This is harder to do on polished stuff, a natural rust is more suitable. like the ones that would form on a nice veritas or LN plane in a humid environment. Even and thin.

    IMG_1006.jpg
    bottom right is a kanna blade that I started the process on and at first it had a wonderful silky gray finish as shown but as I experimented with etching with a citric acid bath and then a way too strong rusting solution I made, it became very pitted and I had to regrind the ura.

    IMG_0992.jpg

    It took about 100 seconds for that to happen. Perhaps it's for the best If I don't find my recipe.

    IMG_0998.jpg

    A little heat and It really chewed through the metal. I think a natural rust from a humid environment with a light pickling from citric acid to start off with would be a good way for a polished cast iron handle.

    I suppose this isn't an easy or fast method. Might not be suitable to your taste at all. I have seen your Kiyohisa (or are they Kiyotada) paring chisels and the Kuro finish on those haunt me, I think images of near perfect Kuro finished tools spark me to do really awful experiments on anything steel or iron.

    http://benchcrafted.blogspot.com/201...cast-iron.html

    I just remembered about this blog post; this may not give the quite the colours you are looking for but isn't very hard to do and noticeable darkens things up.

    have fun experimenting,

    Vince
    Last edited by Vincent Tai; 07-10-2018 at 3:15 PM. Reason: can't seem to grammr

Posting Permissions

  • You may not post new threads
  • You may not post replies
  • You may not post attachments
  • You may not edit your posts
  •