To All, There has been a lively discussion on preventing silver tarnish lately, and a lot of good suggestions were posted, such as enclosing articles in plastic bags.
Unfortunately, sulfur is a very penetrating atom and can pass through a thin polyethylene film quite easily. So ultimately the silver will get tarnished. Silver polish can remove the tarnish, but it will also remove some silver. Eventually the details will be lost and the article will be ruined. There is another way to remove the tarnish without damaging the silver. A simple electrolysis can transfer the sulfur from the silver to another metal, such as aluminum, and leave the silver untouched. The usual method is to place the article in a pan lined with aluminum foil. Add some baking soda and hot water and watch in amazement as the silver starts to shine. You can easily clean large objects this way. Here's an example: http://www.youtube.com/watch?v=G5Qnbn366G0&feature=related Another example uses the same method to clean silver tableware. You can see how quickly the sulfur is removed: http://www.youtube.com/watch?v=CsKLcc13WBo For those who might be interested, the chemistry is easy. First, hydrogen sulfide plus a bit of water combines with the silver and forms silver sulfide: 2Ag(s) + H2S(g) = Ag2S(s) + H2(g) Now comes the magic part. When you place dissimilar metals in contact in an electrolyte, a small voltage is developed between them. You can see which metal takes a positive voltage by looking at the Galvanic Series. You will find aluminum is near the top of the graph, so it takes a positive voltage. Silver is near the bottom, so it becomes negative with respect to the aluminum: http://l-36.com/corrosion.php The baking soda becomes the electrolyte when it is added to water. It does not take part in the chemistry, but merely allows the ions to flow in the solution. The reaction at the silver cathode is 3Ag2S + 6e- --> 6Ag + 3S(2-) This says 3 molecules of silver sulfide accept 6 negative electrons from the aluminum. This restores the silver back to its original state and leaves 3 negative sulfur ions in the solution. The reaction at the aluminum anode is 2Al - 6e- --> 2Al(3+) This says 2 aluminum atoms release 6 electrons to the silver and become 2 positive aluminum ions. Now we have a match made in heaven. The aluminum and sulfur ions could combine and form aluminum sulfide: 2Al(3+) + 3S(2-) --> Al2S3 However, this will quickly decomposes back to the ionic state in water, so the aluminum foil doesn't show any change in color. You simply toss the ions down the drain when you flush the solution away. And now you have nice shiny silver without the elbow grease and without damaging the silver. I am working on a similar method to remove sulfur from the electrodes in a cs generator, but may be running into problems with residual or secondary contamination. I won't know which until a new shipment of silver arrives, hopefully soon. Thanks, Mike Monett -- The Silver List is a moderated forum for discussing Colloidal Silver. Rules and Instructions: http://www.silverlist.org Unsubscribe: <mailto:[email protected]?subject=unsubscribe> Archives: http://www.mail-archive.com/[email protected]/maillist.html Off-Topic discussions: <mailto:[email protected]> List Owner: Mike Devour <mailto:[email protected]>
