replicating/improving this oxidised copper effect

[darron]

i was making some plates for a fuzz, John Lyons style.

before tin plating, i left this one with water on a nearly flat surface. the water rolled off and obviously oxidised it. the colours it made were so pretty though.

somebody out there must have experimented with this before? has anybody got any good techniques? i'm thinking maybe an eye-dropper with drops of water, or using oils.

i've experimented with leaving plates in water. also, with rusting steel wool on top. only briefly and that's the extent of it.

any cool ways i can make some "controlled" colourful swirls like this? or similar effects?

[Seljer]

May try getting some swirly effects if you sped up the oxidation process with a gas torch used on selective areas?

Most of the more 'household' patina'd finishes for copper involve vinegar or ammonia and salt (obviously watch out for the fumes with the ammonia) which tend to give that antique blue/green finish.

[darron]

definitely would like some good ventilation playing with ammonia      haven't played with salt yet. that antique blue/green is a fraction of the colours, like on an old diving helmet i suppose.


how would the gas torch work? heat treat just certain areas before oxidising it? doesn't usually colour things by itself when doing copper work. wouldn't want to get this flimsy fibreglass too hot.

[R.G.]

Search "metal patina copper".

I have a book entitled " The Complete Metalworker", which is a compendium of metalworking techniques for the crafts jewelry trade. There is a lot of info on patinas.

I know that on iron, and I suspect on copper, the swirled rainbow patina is an artifact of the thickness of the oxide layer growing over bare metal when it's too thin to prevent light passing on its own. I believe it's an interference effect from the incident and reflected light through the layer IIRC.

If that's the case, it's a result of differential oxidation going on very briefly at the end of your chemical process before it was stopped.

Copper oxide might not be very durable, and would have to be preserved somehow. I don't know if clear coating would mess up the interference effects, though.

[mistahead]

Jeeeeeesus... reinvent the wheel... oh right - that's why we are here.

Talk to some of the metal art crowd guys - you can get deeply metalised pigment paints and complimentary oxidizing overcoats, art stores and halfway decent paint shops have a good range.

I've an in-law who is a mixed media artist - my god the tricks you can do with a little oxidizer, salt and a kiln...

[John Lyons]

As far as I've found it's one thing to get the color and effect you want and another to keep it that same way
given humidity and further oxidation. Lacquer seems to semi freeze the process but it changes with the humidity etc.
I've used Lye either bought or made (wood ashes and water) and alternating Copper Phosphate (root Killer) and Etchant
dabbed on with a small brush and rinsed and repeated to get the result I wanted (completely inconsistent)  but keeping
the deep oranges and reds is hard to do as far as I've found. They usually turn brown or black and sometimes dull copper
even when clear coated.

[mistahead]

Hence why the suggestion I made isn't bad, from start to end you add an additional metal layer, oxide later, neutralise it and can then coat it.

Its out there guys - ever seen a sculptor who you didn't think was a lazy bum in overalls?   

[R.G.]

Actually, this is a breeze compared to the process for getting red/brown/blue combined "bluing" on steel. That one goes like this:

Get your piece finished and polished to a fair-the-well, cause you can't make it shiny afterwards.
Clean and degrease the piece. Any oils or other contaminants whatsoever will ruin your work, and you won't know until the end. Fingerprints are especially ugly on things like this.
Keep it this clean until you can get it into the oven.
Get a heat impervious container to process the piece. This can be a steel or iron box, or a ceramic enclosure (flower pots have been used).
Bury the finished steel piece in the container in charcoal you've made by roasting fruit pits or bone meal, and soaking the charcoal in a metallic carbonate solution, then drying.
Include a scrap of brown paper to eat the remaining oxygen inside the box.
Seal the box.
Put the box into an oven. Hot oven. Bring it up to 1400-1500C, let it bake for several hours at that temperature.
While it's baking, prepare its bath. Make a salt brine with water, and arrange an air pump to pump in air to bubblers in the bottom of the tank. Leave the top of the tank open.
When the baking is done, take the container out - using tongs, heat protective clothing, face shield, welder's goggles, and so on, because it's white-hot.
Quickly - a few seconds is too much - open/break the container and dump the entire contents into the bubbling brine tank. There may be some steam evolved, and exciting bubbling.  

If you're lucky, the heat, absorbed carbon in the steel, quick cooling and oxygen in the water will oxidize the surface just so, and the piece will be a swirled/mottled mixture of vivid blues, reds, and browns, those being the oxides/thicknesses of the iron oxides that give the colors on the steel.

When it's cool, oil/wax it so it can't further rust and ruin your work.

[haveyouseenhim]

I got the same effect once by accidentally leaving some PCB material a few inches above an open tray of ferric chloride. I have learned to put a lid on my etching dish because the 'fumes' tend to oxidize any metals in the surrounding area.

[darron]

wow. i've just come back from work to a whole wealth of suggestions.


seems like searching "metal patina copper" should lead me in some interesting directions. i didn't really look into it too deeply myself at all, which i usually would, but i was also glad to strike up a conversation here and show the result too


i'd been tinning the boards and giving them a coat of polyurethane. hopefully that will just seal it off bad as noted it might ruin the blues/green or still allow it to oxidise darker down the track. failing that as suggested perhaps just sealing it with some oil/wax. what's the worst that can happen, it get's a little rusty down the track?


so i guess the colours might show intensity of corrosion. lower bands in the spectrum are more intense. looks like a music visualise plugin


i've also has problems with leaving acid nearby. i left some hydrochloric exposed near some VERY expensive machinery which now looks like it's sat on the beach for a year. sigh. lesson learned.


i'll do some research and see what comes out. cheers all

[Seljer]

With most patina finishes you just have to accept that the colour isn't final and will most likely change over time, thats just part of the charm

[psychedelicfish]

I wonder if Hydrogen Peroxide could be used to artificially oxidise metal?

[defaced]

Put the box into an oven. Hot oven. Bring it up to 1400-1500C, let it bake for several hours at that temperature.

Why so hot and so long?  That's delta ferrite land which I can't make an obvious connection why that would be better than austenite (which is formed at a much lower temperature) for this application. 

[R.G.]

Put the box into an oven. Hot oven. Bring it up to 1400-1500C, let it bake for several hours at that temperature.

Why so hot and so long?  That's delta ferrite land which I can't make an obvious connection why that would be better than austenite (which is formed at a much lower temperature) for this application. 

I don't actually know. I think that the colors were a side effect of the original process.

The real objective of the process was case hardening gun parts.  It was a traditional process for hand-crafted guns back when a gunsmith would make or modify everything by hand. Low- or moderate-carbon steel was the base material, and the hard-coating was for mechanical durability, and then blued for corrosion resistance. I believe it was an accident when someone noticed that instead of boiling the metal in a nitrates salt bath for some hours that the case hardening process itself could produce an oxide finish that was attractive.

Of course, today guns are manufactured with a carefully controlled process for bluing, and the tinkering to get blue/red/brown swirls is way to expensive and requires too much tinkering and hand labor, even for low-labor-cost places. So the process has become a little-known very-high-priced option for things like hand-made high end shotguns and such.

The objective was to diffuse carbon into the outer case, then harden it with the quench. The oxide was a fortuitous side effect. I believe that the optimum temp for swirled colors is lower than the optimum temp for case hardening, or best diffusion or something.

[defaced]

Ok, case hardening, that's a different ball of wax than just making pretty colors.  I could see performing that operation at high temperatures advantageous because the speed of diffusion of carbon into the matrix is faster because of the BCC ferrite structure and increased energy of the system.  Or it may be for better carbide formation - I'm not terribly familiar with bluing, but there's only so many options when you have steel that hot and you're adding carbon.

The pretty colors occur at much lower temperatures, but is alloy dependent.  I do alot of pre-heating of steel alloys prior to welding, some are fairly low chrome which start to discolor around 300F, others which are higher chrome don't start to discolor until 450F.  If they're held at this temperature for long periods of time (hours, days), the colors continue through the spectrum as if they were heated to a higher temperature and ultimately end up a nice dull gray color.  What starts out a nice shiny freshly machined pieces of metal turn into dull gray hunks of weldment when they leave the lab.  

[mistahead]

I wonder if Hydrogen Peroxide could be used to artificially oxidise metal?

Yes but why bother with the price.

Heavily salt water (saturate it) drop the metal in, cut the jack off a big wall wart.... ahhhh dammmit.... who can help me finish the trick for oxidizing this way... I forgot which lead.

Haven't done this since I was 14 and also making a lot of aluminium dust...

[Joe]

I used to copper plate boxes using this formula:

-Copper Sulphate Pentahydrate (Root Kill) (1 tsp)
-Sodium Carbonate (Washing Soda) (1 tsp)
-Cream of Tartar (1 tsp)
-Water (enough to cover pedal)

Do this after drilling holes etc. Use a stainless steel saucepan deep enough to hold your enclosure. I don't think going over 1 tsp for the chemicals helps much, and only makes more of a mess. Perhaps even less will do.

Dissolve the copper sulfate into the water and bring just to a boil, but not too hot. Lower the pedal enclosure into the water, and dump in the other ingredients. Swish the enclosure around until it's plated. (Flush the leftover solution down the toilet, it cannot be reused.)

IIRC the plating is thicker and blacker as the temperature goes up. You can also modify the outcome the same way you would clean pennies, with a vinegar/salt solution. (You can erase the whole thing this way if you don't like it.) Lacquer the finish.

Usually the outcome is a lot of brownish oxide but with a lot of colors mixed in. The temperature has a lot to do with the colors. I'm not sure if this will get the exact result you're looking for but is relatively easy.

[mistahead]

You could use electrolosis (spelling?) and replace the sodium chloride in my suggestion with copper sulfate... I still don't recall which lead you need to touch the metal (+ or -) but the other just floats in the solution.

Pretty sure its positive terminal attaches to target metal, negative floats in solution... but I could be thinking that because pos/neg are actually counter-intuitive...

[darron]

screw this! i'm not interested in plates any more... I'd rather plate the whole enclosure and have the effect!



the electro-etch seems a bit excessive when all that was required was a bit of water exposed for 15 minutes in the sink. THOUGH... now that I think about it, exposed ferric chloride was right beside it.


will definitely play with some highly salts saturated blends. that seems like a winner. i was more interested in application techniques like perhaps spinning, or dropping, or draining in a special way. haven't had time to look into R.G.'s thoughts just yet but that will probably point me to the right info

[mistahead]

Give the submerge and wire-up method a go, really, you need less salt concentration and its FAST...