I hope some knowledgable people out there can give me some advice!
I'm intending to use copper microbore (8mm & 10mm) to make a "twisting garden sculpture. I'd like to know what colour this will end up whe left outside, as I don't know whether microbore is "annealed" o "enamelled" or not treated at all.
I may also incorporate some smaller wire for decoration - I' considering Enamelled Copper Wire (2mm) which I assume would sta "shiny" even outside? Or possibly annealed copper wire (like that use for binding bonsai trees!) - I believe the latter would end up a dul sort of brown colour - am I right? (probably not!!)
Many thanks in advance of any kindly forthcoming help..
I hope some knowledgable people out there can give me some advice!
I'm intending to use copper microbore (8mm & 10mm) to make a "twisting garden sculpture. I'd like to know what colour this will end up whe left outside, as I don't know whether microbore is "annealed" o "enamelled" or not treated at all.
I may also incorporate some smaller wire for decoration - I' considering Enamelled Copper Wire (2mm) which I assume would sta "shiny" even outside? Or possibly annealed copper wire (like that use for binding bonsai trees!) - I believe the latter would end up a dul sort of brown colour - am I right? (probably not!!)
Many thanks in advance of any kindly forthcoming help...
Sort of ruins the point of using it! It will go greenish after a long time, depending on conditions. He could of course use the odd bit of brasso to polish it up ;o)
No. copper goes red or brown from oxides fairly quickly, but prlonged exposure to rain causes that to turn to carbonet.
You can use some chemical - can't remember what it is - to blacken copper as used in copper bas relief work, but you need a lacquer over the top to prevent it going the carbonate route.
It's annealed, not enamelled. It'll go dirty brown quite quickly. If you're after a verdigris finish it won't, if that's the last thing you want it will :-)
Acid flux left around soldered joints seems to give verdigris quite quickly.
Enamelled wire would probably keep its colour longer, but wouldn't then match your sculpture. You could probably acquire un-enamelled wire of various grades for the asking from an electrician or skip: just strip it from PVC cable.
I tend to think they put some laquer on the pipe at production to keep it shiny. I do outdoor sculpture with copper and first use fine steel wool to get down to bare metal, chemically clean with good old malt vinegar (how people use that stuff as food flavouring !) and then with a bit of practice apply a cupric nitrate solution. Hey presto 3 years worth of patination in an hour. If you want to keep it a plain old brown just apply some wax to keep the acid rain away.
I think the route that copper gioes is basically surface oxidation to cuprous oxide, which then works with carbonic acide to go to copper carbonate.
Copper sulpate as such is blue, not green and water soluble - though sulphide is very black IIRC.
All I know is that in the presence of hard water (leaks/condenstaion) on my plumbing green deposits occur very quickly - especially on HW pipes where temps are high. In fact condensation also turns pipes green.
My experiences with domestic plumbibg are if he copper is left indoors is slowly goes brwon with an oxide later, but if it gets damp outside it rapidly goes green. We are in a hard water area so that may explain the arpidity of carbonation on leaking pipes.
Annealed pure copper will remain soft indefinitely, but most aluminium alloys will "age harden" afterwards, no matter what you do. This is inherent in the alloy's behaviour, it's not a question of "proper technique"
Copper left alone outside will darken to a tolerable dark patina, but it will take an age and is likely to have pale green spots on it. You're unlikely to get a greenish deposit overall, unless there's water or tree sap running over it, but you'll get at least one visible splodge of it. To avoid this, apply a deliberate patina immediately. Applied patina is more stable against discolouration than bare metal.
For an easy life, spend a fiver on a bottle of Liberon's "Tourmaline brown" antique patina for copper (from Axminster). It's an easy cold process - not the best in the world, but it's the best you can do for a fiver, working cold, and without shopping for awkward to locate chemistry.
If you want to colour copper, then read these two books:
"The Colouring, Bronzing and Patination of Metals"
This is _the_ book on colouring non-ferrous, non-exotics. Expensive, but worth it. Well known, so any decent library should have access to it.
Tim McCreight, "Color on Metal"
Cheaper, but less comprehensive. Worth reading if you happen across it.
Two relatively simple copper recipes with easily obtained ingredients are these:
Glossy dark brown (recipe 3.69 in CB&P)
copper carbonate 125g .880 ammonia 250cm^3 water 750cm^3
(It may be easier to replace both water and ammonia with 1litre of 26% ammonia, which is commonly available in hardware shops)
Simmer in a warm bath of this mixture at 50°C for around an hour - the colour develops slowly. Wash in hot water, then dry by tumbling in a box of sawdust . Wax afterwards.
Matt dark brown (recipe 3.70 in CB&P)
cooper sulphate 125g ferrous sulphate 100g glacial acetic acid 6.5cm^3 water 1litre
Boil for 30-40 minutes. Wash in hot water, then dry by tumbling in a box of sawdust . Wax afterwards.
Both of these recipes use common chemistry that's of little toxic hazard. However the ammonia process needs good ventilation and keeping away from aluminium (For comfort I wear a full-face mask too - a half mask is useless, as ammonia will enter via the eyes). Acetic acid in this strength is corrosive and irritating, so wear gloves and keep it out of the eyes.
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