On Fri, 08 Apr 2005 07:27:24 GMT, "al"
wrote:

Properly annealed metals should retain their annealed appearance almost
indefinitely.

What's an "annealed appearance" ?

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"
http://www.amazon.co.uk/exec/obidos/ASIN/0500015015/codesmiths
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"
http://www.amazon.co.uk/exec/obidos/ASIN/1893164063/codesmiths
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.

--
Smert' spamionam