Cyanides attack it, but they aren't acids
Hi Peter and all, I am not a chemist or a scientist and after your
reply about cyanides I started to reflect on. I sometimes use
potassium cyanide to clean gold from oxydation, mostly on chains. I
have never think that this substance can attack gold or other metals.
May be you was talking about another cyanide or maybe I have never let
metal enough time into it to note it. Would you please give more infos
about it. Thanks for your realiable advises. Vincent Guy Audette in
Quebec city
Hi Peter and all, I am not a chemist or a scientist and after
your reply about cyanides I started to reflect on. I sometimes use
potassium cyanide to clean gold from oxydation, mostly on chains. I
have never think that this substance can attack gold or other
metals. May be you was talking about another cyanide or maybe I have
never let metal enough time into it to note it. Would you please
give more infos about it.
Vincent,
Either Potassium or Sodium Cyanide solutions will dissolve gold,
silver, or copper. Not as rapidly as strong acids will, but still,
quickly enough to be notable. For it to go faster, use an electric
current to “strip” the gold into the solution. Like that, cyanides
can be used to quickly and efficiently etch patterns into gold or
silver in the same way that acids are used as etchants, and the etch
is often smoother and more even than with acids. Using cyanides as an
etchant does mean you need more secure masks, as the strong alkaline
nature of cyanide solutions will break down many of the materials
that can be used as masking agents when etching with acid. The effect
of just dipping gold items into cyanide is not so visibly obvious as
an etching one, since it’s slow, and there is no bubbling or obvious
action. The oxides are dissolved more obviously, but the gold is also
being removed. It doesn’t so quickly make it all dull, so you may
not be aware that metal is being dissolved. But it is. Take a piece
of thin gold sheet metal or wire, and leave it in a cyanide solution
overnight. Then use a micrometer on it the next day, and you’ll see
it will have been slightly reduced in thickness. If the solution is
hot, it acts much more quickly.
Peter Rowe
Peter-- Is there a resist that can be applied to the gold to etch only
certain areas with the cyanide? Probably a newbie question, but it
could have interesting applications.
Thanks Katharine in foggy Marin
etch resists for use with cyanide are a bit trickier than with acids,
since the highly alkaline nature of the cyanide solutions make them
supurb cleaners, and they tend to lift off some resists. However,
I’ve had good luck with the old standard asphaltum “hard ground” or
varnish types of resist used for printmaking where you are manually
scratching through the resist to open up areas to etch, and
commercially, some of the photoresists, such as Kodak KPR, I’m told,
also work. Beyond those two, either someone else will have to make
suggestions, or you will have to either try them out, or better,
simply ask the manufacturers of the products you would like to use…
Peter Rowe
Coats Australia make an acid resist printing ink which is soluble in
turpentine. Great for screen printing and also behaves well in cautic
solutions when etching aluminium so should with stand the alkaline
conditions of the cyanide.I willl post the details later as they are
not with me at present. Cost per kilo was approx $42 Aust. David Mcleod
Anne Jackman & David McLeod
Granton Studios
Harington Point Road
2 RD
Dunedin
New Zealand
ph: 0064 3 4780 635
email: @Anne_Jackman_David_M