Ammonia in sawdust, or a small container of it sealed in a
plastic bag with the copper item will give you the same ( or
similar) patina, without upsetting the cats ;-)
G’day; As Christine implied,. it is the ammonia and primary
amines in stale urine which cause the patina reaction. These
substances are produced by bacterial attack on various substances
in the urine; fresh urine is completely sterile unless the producer
has a virus which can get through membranes that bacteria in the
body cannot. Urine is a really excellent culture medium for many
Here’s a couple more suggetions;
Dampen - not soak - a small piece of sponge with undiluted
household ammonia (from the supermarket) and place it in a sealed
plastic bag with the object to be patinated which must be clean and
grease free. If it is firstly wiped over with a solution of copper
sulphate or very blue old pickle, and allowed to dry the patination
will be more rapid.
Obtain some solid pieces of ammonium carbonate (your local
pharmacist?) and use that instead of the sponge - less messy.
Ammonium carbonate is used in smelling salts., and gives off ammonia
. I don’t think normally fastidious people want to muck about with
bodily wastes when there are good alternatives available.
Cheers for now,
John Burgess; @John_Burgess2 of Mapua, Nelson NZ