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Sparex turns silver black


#1

Hi Folks, I could have sworn I saw this question on Orchid before, but
can’t find a trace of it in the archives. Since I had never had the
problem before, I don’t think I bothered to follow the thread… sorry
for any redundancy, but HELP!

My pickle is starting to turn sterling black. No longer coming out a
dull white. The longer the silver stays in, the blacker it gets. I am
using Sparex in a crock pot. The pickle isn’t that old… maybe a
few months… hasn’t taken on the telltale green-blue tinge of spent
pickle. It has evaporated a bit, had more water added and evaporated
some more, but that’s nothing new for me. No known contaminants, other
than the possibility of a couple dead bugs. I only use stainless steel
binding wire… and this doesn’t appear to be a plating problem. I use
water based Wite-Out as an anti-flux, boric acid, green liquid flux
(primarily). That should be about all that’s in there.

Should I just neutralize it, dump it out and start with a fresh
batch, or is there something else going on here I need to know about?

Thanks in advance,
Dave
Dave Sebaste
Sebaste Studio and
Carolina Artisans’ Gallery
Charlotte, NC (USA)
dave@sebaste.com


#2

your pickle is contaminated - perhaps a steel utensil was placed
in the solution - replace it.


#3

You have been keeping the stuff too long! You are getting metal
sulfides in the bath among which are the black silver sulfide. You
sulfate bath is an interesting mix of metal ion sulfides that would
make a nice “unknown” for a qualitative analysis student…

Jesse


#4

Dear Dave, My guess is that some how some iron (steel) got in there.
I know when this happens my sterling copper plates and I think turns
it black as well. Maybe tweezers got dipped in there or something.
Neutralize it and start with fresh. Sam Patania, Tucson


#5
    My pickle is starting to turn sterling black. ... The pickle
isn't *that* old... maybe a few months... hasn't taken on the
telltale green-blue tinge of >    spent pickle. ....No known
contaminants, other than the possibility of a couple >    dead
bugs. 

G’day Dave; Sparex, which is sodium bisulphate will not, of itself,
cause silver to blacken. The blackening of pure or fine silver is
caused almost entirely by the action of sulphur compounds on it.
Copper in sterling silver will also blacken with the action of
sulphides, but copper has a black oxide too, which silver does not.
Sparex or sodium bisulphate will dissolve copper oxides, sulphides,
and silver sulphides. So there must be some contamination of the
pickle. But you did put in that sentence about 'a couple of bugs.'
Well, for a start, most bugs do contain sulphur compounds in their
make up, which break down in acid solution over time and that is one
possibility. But if ‘bugs’ can get in what else can get in unknown to
you?

My suggestion is that you stop buying an expensive pickle and buy the
pH adjuster sold by shops who sell equipment for spar and swimming
pools. They sell it by the pound, not by the ounce! It is the same
stuff; sodium bisulphate and is very cheap indeed. So cheap that you
can economically replace it much more often, but even so, you should
keep the pot covered when not in use. – Cheers now,

John Burgess; @John_Burgess2 of Mapua Nelson NZ


#6

As we all know there was always that one person in class that thought
he/she could get by or thought the rule was not true. Remember the
hair that stood up on our neck when it turned out to be our items
that were contaminated, Ahh the good ole days. Great to read news
from you girlfriend. Eager to hear more. Hee Hee Pat