Black residue on tumbled silver

I have been using the Rio rotary shot tumbler for about a year with
great results. Recently, however, I have been getting a black residue
that is burnished onto the surface of the silver pieces. It resembles
fire scale and is almost as hard to get off. I use Rio burnishing
liquid mixed to the right proportion. I realized that the black
coating was coming from the rubber “O” ring seal at the lid. I called
Rio customer service and told them my theory and their reply was that
was the first time they had heard of this. They are going to try to
find another “O” ring for me. In the future I will put a layer of
saran wrap over the hole before putting the top on so that the
burnishing compound can’t contact the seal.

I determined that the seal was the problem when I wiped it with a
paper towel and got a very black streak on the towel. This residue
coated the inside of the clear plastic barrel and created the
nastiest black foam inside as it tumbled. I ran a few pieces with
laundry detergent and had no problem with the residue.

I was just wondering if anyone else has had a similar problem with
this unit.

Alburn Sleeper

I too had that problem. Use “Simple Green” cleaner to clean your
shot. Get it at the grocery store.


We get the black coating every month or two, especially end of
quarter when students give tumblers heavy use. I clean our stainless
steel shot tumblers with a few tablespoons to a cup of baking soda
depending on tumbler size. Rinse the out the tumbler and shot and
refill tumbler with shot, water and baking soda. Run tumbler for
about three hours.

WARNING!! Keep tumbler in a container or someplace waterproof. Ours
lives in plastic storage container. Pressure builds up and may pop
the lids of the Lortone and one bolt type tumblers. Bigger tumblers
with the multi-bolt on lids hold better. If still has black coming
off lid and inside barrel repeat the baking soda tumble. This should
clean the tumbler and shot.

I have tried Coca-Cola, Sodium Hydroxide, or Simple Green
(separately - NOT mixed together) Baking soda has worked the best
for tumblers here.

1 Like


I have also had the problem of black residue coating on my sterling
silver after burnishing with stainless shot. This also happened to
me after many years of successful tumbling using Rio burnishing
liquid. I tumbled in sudsy ammonia to clean up my silver jewelry, my
stainless shot and my barrel.

I never did find out what caused the residue but I have three

  1. The Rio burnishing liquid is attacking the black rubber barrel.

  2. Contamination with the oil I use to lubricate the tumbler.

  3. Contamination by polishing compound on the jewelry.

I now mix up the Rio burnishing liquid at half strength and use it
that way. I make sure that my silver jewelry is clean and free from
contamination when it goes into the tumbling barrel and that no oil
is transferred from the outside of the barrel.

I have not had the problem since making these changes and I am still
using the same tumbling barrels.

I also told Rio Grande about this problem and they recommended
tumbling in sudsy ammonia to clean up jewelry and shot.

David Luck
627 Center Street
Iowa City, IA 52245-3008


I had this problem a couple of years ago. I tried everything using
all sorts of soap compounds to clean my tumbler. I took all of the
shot out and washed it really well and nothing worked. Finally I
heard from a friend that I should run a little bit of Coca Cola in my
tumbler every now and then. I did and it worked! My tumbler is back
to it’s shiny self! Thank God I don’t drink Coke!

Delias ; )

When I was in Norway, I found that adding a little citric acid
(crystals, can buy at grocery store), prevented the polishing
compound residue from sticking to the silver.


Delias thanks for that. I can live with the coke thing, but if
someone suggests that Corona does the same thing the country could be
in trouble.:):slight_smile:

Dave thanks for that. I have isolated my problem to the black rubber
"O" ring seal. I ran the last batch with a piece of saran wrap
covering the seal and it worked fine. Al.

When tumbling either with a rolling or vibratory tumbling and which
ever media you choose. You must use some form of lubication, most
times the media supplier will have either a product or some
suggestions for what to use.

When you you get done with a run you must clean the items that are
tumbled, the can or barrel and the shot. No matter what you are
using wash it till the water runs clean. Washing the shot in a wire
strainer from the dollar store will let you have a couple. If you
store the shot dry then placing a towel on a baking sheet with the
shot spread out in a thin layer till it drys. If you store it wet in
a plastic jar in the recomended lube till the next time you must
wash the shot and barrel out everytime. No execptions.

If you wipe most any rubber product with a cleaner you probably will
get some carry over. The most common black scum on silver is from
not washing the shot and equipment good enough between uses. Some
cheap rubber rings and gaskets can be affected by any petro-based

If you want to lube or lightly grease the gaskets or o-rings use a
silcone based grease or go to a plumbings supply house and pick up a
tin of sexhauer (brand name) plumbing valve/faucet grease. a tin or
tube will last a long time.

been there, done that and broke it!