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Black residue on tumbled jewelry


#1

Hi All,

My name is Max Goodman, I’m a jewelry designer and educator, and I
run the jewelry studio at 3rd Ward in Brooklyn, NYC
( http://www.ganoksin.com/gnkurl/1b8 ). We recently inherited a large
scale tumbler, along with what I presume to be about a pound of
steel shot. The tumbler is in good shape, and loads from the top.

Having never owned a tumbler before (where I went to school we had
mass finishers, but they all took ceramic media, not steel shot), I
was eager to find out all I could about working with this one. I
filled it with water to about 3/4" above the steel shot, and added
dawn soap as per directions I found online. The first few rounds of
tumbling went fine - because I intend to use this for my lost wax
casting students, I threw in a couple of clean sprues, and they came
out looking shiny - they were silicon bronze. I then put in a silver
ring, and noticed some mild discoloration, almost an oxidizing.
Unsure of what to do, I tried one more piece, and to my dismay the
black tarnish-looking finish increased. I switched out the water and
rinsed the steel shot using a screen, then tried again, to no avail.
Any clues on what I’m doing wrong, or what chemical combo might be
growing this sticky black finish? Thanks!

Sincerely,
Max Goodman


#2

Max,

What color is your tumbling barrel? Black rubber? And how long are
you running it? If you’ve got a black rubber barrel, what may be
happening is that the longer you tumble, the media will rub off some
of that black rubber and then deposit onto your jewelry. That black
rubber for tumblers was not such a hot idea, I’m thinking. In ours,
we use a stainless steel asst. media, with water and a half cap-full
of ShineBrite burnishing compound concentrate, made by Eurotool. When
we are polishing (burnishing), we only run our tumbler for about 15
min. and get a beautiful shine. Our liquid gets dumped after each 15
min. session.

If you run it for hours, we’ve noticed the black coating appears,
much like you’re describing. That’s why we keep our running times
relatively short in those black barrels.

Hope that helps.
Jay Whaley


#3

Max, there is a thread about this in the archives if someone can
explain how to find it.

John Moe


#4

Hi Max - order up some solution specifically designed for tumbling
steel. The Dawn is alkaline, you need a mildly acid solution with
surfactants as well as cleaning agents. I use Rio Grande’s Sunsheen
concentrated solutions. You would fill the tumbler to just below the
top of the steel with diluted solution. Change it every time you run
or at least once a day. It gets dirty.

To clean up your mess, use a can of regular Coke that you either let
sit or heat to remove carbonization, and run your steel in the
tumbler. The acids in the coke will do a good job of cleaning the
black gunk. Rinse the sticky mess well and proceed.

To learn more, read the book I wrote on the subject - Tumble
Finishing for Handmade Jewelry. Gesswein, Frei and Rio Grande and
others carry it. It has a lot of on how to use tumblers,
including “cookbook” recipes for times and finishes.

Judy Hoch.


#5

I’ve dealt with the black residue and in my case it came from dirty
shot or perhaps dirty, worn-out soap. Wash your shot and start
fresh. It solved the problem for me.

Dick


#6

I’ve read about this happening, but have never (so far) had it
happen myself. I prefer to use Rio’s Sunsheen over Dawn. It IS
possible to break down the rubber barrel with time - lots of time!

I run mine anywhere from 30 minutes to a day or two, depending on
what I’m doing, and change the solution when it gets dirty - not
that often, actually.

I believe I’ve read that running Coke in the barrel will help clean,
but do some searching online first! Don’t take me word for that!!! I
do know I’ve read that there IS a way to clean it up.

Beth Wicker
Three Cats and a Dog Design Studio
http://www.bethwicker.com


#7

Stuller sells some liquid steel shot cleaning soap and also liquid
tumbling soap. The tumbling soap has a pH of 4 and the cleaner has a
pH of 10.


#8

I’ve noticed if jewelry is dirty and lots of tarnish on metal, it
will turn my clean tumbling solution to a greasy black, and leave my
very old ( but still very good ) carbon steel shot greasy. I have to
run a couple cycles with shot cleaner ( powder form) and change it
at least 2-3 times. Another oldie but goodie is to pour vinegar into
your barrel and add a teaspoon of baking soda, and run for 15-30
mins to really clean your shot. I’ve had to ask some of my students
to clean their jewelry with Tarn-X to remove the tarnish and degrease
the metal a bit before they do a tumble run in my tumbler,
otherwise, we run into the greasy shot issue. I’ve used household
degreaser to degrease my shot on occasion. Now, I use a shot cleaner
from Contenti that works pretty good. Since my steel shot is 26 to 40
years old, I have to use 920 compound from Rio or Contenti for the
rust inhibitor since it is too much of a hassle to use steel shot
storage solution. Personally, as long as I take care of my steel
shot, why bother upgrading to stainless steel? It’s lasted this long.
I use clear plastic barrels so I can really see how the shot and
solution looks day to day.

Joy, who loves old tools and uses the frequently.