Two-tone effect, and Heat Colouring on Steel Prints

Discussion in 'Finishing Techniques' started by bengabel, Jun 17, 2016.

  1. NoahLI
    NoahLI Well-Known Member
    Cool! I'll definitely try it out when I get the kingfisher printed. Have you tried quenching in oil? polishing wise you start at a very fine grit? 1000? 2000? and work up to 6000?
     
  2. Ontogenie
    Ontogenie Well-Known Member
    What an amazing experiment! I especially love the one with the gold/silver contrast and the one that has been blued. I'm also curious to hear more details about the polishing. I might try it with some of my pieces someday.
     
  3. stannum
    stannum Well-Known Member
    You forgot around 40% is bronze.
     
  4. Wow, truly excellent. The two-tone effect is very impactful, they all look great... Vaguely recalling Orin from The Neverending Story... Love the polished item resting on kelp!
     
  5. tiancode
    tiancode Member
    Let me confirm with you, that in the first a few photos (especially photo#3), what's blued is the gold layer, not the steel surface?

    I have never thought of gold being oxidized to add color. Maybe not a lot of people tried!? This just opens up endless opportunities. Thanks so much!
     
  6. bengabel
    bengabel Active Member
    Hi everyone, thanks for your comments. Just to clarify a few points about this process:

    The gold isn't reacting with anything or oxidising - it can't. (Thats why we love gold so much, it doesn't oxidise)

    So the two components of the model that we are interested in are the stainless-steel and bronze.

    Stainless-steel doesn't easily react with much - which is why we call it 'stainless'.
    But it can , if heated enough, slowly create a thin surface oxide layer that acts as a diffraction grating , making it look yellow/blue/purple. This is a well-known effect - you can read about it on the web:
    http://www.bssa.org.uk/topics.php?article=140

    Because stainless is so unreactive, this oxide layer doesn't grow over time and the colour is stable in air.

    Bronze on the other hand reacts well with other things, so you can use traditional chemical patination techniques on it. These however need coating/waxing to prevent further oxidation/reaction over time.

    Because our model is made of a mix of the two things, you see both effects. When you heat it, the stainless component can colour, while the bronze component will darken.

    The trick seems to be to stop heating after the stainless has coloured but before the bronze darkens . . .

    Note:
    The different steel materials do seem to have a different stainless/bronze ratio. If you file into a Bronze Steel Model, its that bronzey colour inside. If you file into a Gold Steel or Grey Steel model, its bright silver inside.

    The coloured surfaces - Matt Black, Grey, appear to be chemical patination surface layers.

    So for heat-treatment the best starting point is Stainless Steel or Gold Steel , whereas for patination experiments you should start with Bronze Steel.

    Hope this inspires you all, do post pics here of your results!
    Ben
     
  7. mkroeker
    mkroeker Well-Known Member
    Actually I am wondering if the thin gold plating may be the surface layer that can be structured to give the color effects (no need to build an oxide layer first in this case). And I would not expect different bronze content of the bulk material to correlate with surface treatment - more likely to be related to part geometry perhaps, or just too small sample size ?
     
  8. bengabel
    bengabel Active Member
    The gold is a bit of a red herring. We know we're not changing the gold layer. So that's not responsible for the colour change. And its thickness is much, much thicker than the wavelength of light too, so you can't get that effect that way. The gold just sits there being gold.

    The only influence I can imagine the gold having is that it might slow down the oxidation of the stainless , making it easier to stop at the right temperature/colour.
     
  9. NoahLI
    NoahLI Well-Known Member
    got a couple of steel prints, one plain, one gold plated. gonna practice a few more runs on some stainless spoons before I point the torch at the prints. :D

    It's a very delicate process, a second too much and the color changes past what I was aiming for.

    Edit: must be my luck of the draw... no matter how much I polish my prints have slight yellow tint from the bronze.
     
    Last edited: Aug 27, 2016
  10. NoahLI
    NoahLI Well-Known Member
    DSCN8870.JPG

    Gave it a go.. actually close to a dozen go's. Can't seem to hit the temp mark without overshooting, I get to the deep orange color then next color I see is light green/blue going toward gray. Can't seem to get the dramatic blue/violets you are getting. I think butane and propane torch is just too much heat.

    After slooowly heating this one about 4" ~5" away from the visible flame for what seemed an eternity, I got a dark gray that looks rather nice after going over with polishing wheel, so I figured I keep it.

    I'll experiment more with the other print, maybe try more aggressive approach this time not letting the entire piece get too hot.
     
  11. PacoSako
    PacoSako Member
    Cool!! Beautiful.
     
  12. fouldobaggins
    fouldobaggins Member
    Really interesting work this, and the results are stunning! Hoping to rummage up the courage to try it myself someday.. Thanks for all the info, definitely keep it coming!
     
  13. bengabel
    bengabel Active Member
    Nice birds. OK, yes it can be problem with the piece retaining heat and carrying on cooking...

    Try heating slowly and then throwing in a water bath as soon as you see straw-yellow. Should stop it there.

    (none of mine have shattered yet!)
     
  14. bengabel
    bengabel Active Member
    And, with your one that has 'gone over' it might be worth painting it with plumbers flux and letting it sit for a while, then heating gently and cleaning, the flux might eat off the oxide layer, so you can try again from the start.
     
  15. seriaforma
    seriaforma Well-Known Member
    Very cool!
     
  16. NoahLI
    NoahLI Well-Known Member
    Tried it a few more times last night... mixed results, nothing picture worthy. Did get some violets and spots of blue, dunking it in water seem to cause much of the oxidation to flake off and I end up with a much duller finish, any kind of polishing takes off whatever's left and I'm back at a dark brown. Plus side is residual oxidation really makes the textural details pop after polishing. I'll just keep trying till I run out of propane or till I get something I like. :D

    Maybe I'll give nitre bluing a try. Seems easy enough to do.
     
  17. bengabel
    bengabel Active Member
    I've done a few now, and I think those of you having trouble with this are heating too hard and too fast. It definitely works best with the Gold Steel.
     
  18. bengabel
    bengabel Active Member
    Here's a particularly satisfying result; Ported Triwing sculpture in Gold Steel, heat coloured and then repolished to give steel highlights.

    Photo is not retouched in any way, taken with a Motoroloa Moto E 2015. IMG_20161119_132221384~2.jpg
     
  19. Lilichi
    Lilichi Member
    This adds a LOT of pretty detail! I've just tried to give a stainless steel part a patina with vinegar and salt, that adds some color variation, but I think your way of doing it is much prettier, and cleaner too.

    You really should make these thinner and maybe slightly smaller, they would do great as jewellery, especially as pendants! in fact, I thought they were pendants, until you called them 'pocket sculptures' ...