How does aluminum foil clean silverware

A. The principle behind this is that most metals corrode with exposure to oxygen. For example, iron rusts with time because of its exposure to moisture in the air, oxygen. You may also have noticed that cars in the northeast rust a lot faster because of the salt used on the roads in winter. The whole process involves electrons moving between the metal and oxygen atoms. It happens spontaneously with most metals (gold being a notable exception). Silver does pretty much the same thing, only that tarnish is the combination of silver with sulfur [affil links] and not oxygen. Silver is special with its more complex reactions, but the principle by which silver tarnishes is the same by which iron rusts.

Aluminum also does the same thing, only it happens more readily than silver...(see where this is going?)

So we need to move the electrons to and from the metals and we need a metal that will take the electrochemical abuse for the silver. The aluminum takes the hit for the silver, and the salt water allows the electrons to move between the silver and aluminum. I would explain more, but this is not a general chemistry article.

This of course raises the question of why airplanes (which have aluminum) don't dissolve in mid flight...

A. Explanation: Silver tarnishes because it undergoes a chemical reaction with sulfur-containing substances in the air. Silver combines with sulfur to form silver sulfide, which is black, and darkens the silver.The silver can be made shiny again by removing the silver sulfide coating from the surface.

Two ways to remove the silver sulfide are to: remove it from the surface, or reverse the chemical reaction and turn silver sulfide back into silver. The first method involves polishes that remove some of the silver during polishing. The above demo uses a chemical reaction (which is sped up by heating the water) to convert the silver sulfide back into silver, without removing any silver.

Aluminum has a lower ionization energy (energy required to remove electrons from an atom of the element) than silver. As a result, aluminum is oxidized (loses electrons and oxidation number increases), and silver is reduced (gains electrons and oxidation number is reduced). Depending on the amount of tarnish, the silver will be bright and the aluminum foil may be brown with tarnish (aluminum oxide), in a short while. The silver tarnish is "transferred" to the aluminum via reactions, which occur instantaneously, as follows:

3Ag₂S(s) + 2Al(s)+ 3H₂O(l) => 6Ag(s) + Al₂O₃(s) + 3H₂S(aq)

silver sulfide + aluminum + water => silver + aluminum oxide + hydrogen sulfide
(* Note, this reaction can be done without the baking soda, but it takes longer to see results).

The baking soda (sodium bicarbonate) reacts with the (sulfur-smelling) H₂S:

3 NaHCO₃(aq) + 3 H2S(aq) => 3 NaHS(aq)+3 H₂O(l)+ 3 CO₂(g)

baking soda + hydrogen sulfide => sodium hydrosulfide + water + carbon dioxide. The CO₂ gas can be observed escaping from the most tarnished parts of the silver.

The silver and aluminum must be in contact with each other because a small electric current flows between them during the reaction.This type of reaction, which involves an electric current (because atoms are charged), is called an electrochemical reaction, and is used in batteries to produce electricity.

A. Hi, David.

Tania is apparently indicating whether the compounds are solids, liquids, gases, or ionized in an aqueous solution.

Baking soda merely supplies conductivity. Similar results can be had with washing soda [on eBay or Amazon] , Spic and Span [affil links], or other conductive salts. Although hydrogen sulfide is poisonous, Paracelsus reminded us that everything is poison; it's all in the dose. Eggs release hydrogen sulfide as well.

Regards,

A. Hi. The silver does need to be in contact with the aluminum. For silver sulfide to be reduced to silver, electrons must flow to it from the aluminum, and there needs to be metal-to-metal contact so the electrons can flow. Ions flow through the liquid, electrons flow through metal.

Regards,

A. Hi, Rod. There is no end to the size of containers. Bathtubs or stoppered shower areas can accommodate rather large trays. But I have heard, without verifying, that scrubbing the tray with the aluminum foil wetted with the washing soda [on eBay or Amazon] will work. Good luck.

Regards,

A. Hi. Some people say the reaction is instantaneous in hot to boiling water anyway.
Sure, external electrical power can be used to drive an electrochemical reaction ... it's done in electroplating and other processes ... but it makes a simple reaction more complicated :-(

Regards,

A. Hi Soren. To my knowledge, brass and bronze don't become sulfided like silver, so the reactions would be different. I believe that copper "bright dips" can be used on brass and bronze. The bright dips are comprised of an acid and an oxidizing agent. Nitric acid is one example, sulfuric acid plus hydrogen peroxide is another. But here we're talking about materials that are far more dangerous and less suitable for home use than aluminum foil and washing soda [on eBay or Amazon] . Good luck.

Regards,

A. For the large serving trays, scrubbing with aluminum foil works for me. For my jewelry, I use an old toothbrush with foil wrapped around the handle end. Use the brush end to soak crevices with solution, then gently scrub with the foiled handle. When possible, I do this with the item IN the solution.

My formula is 1 cup near-boiling water with 1 T each salt, soda, and liquid dish detergent.

I'm no chemist, but when cooking, baking soda can be substituted with baking powder and salt. Both soda and salt may create a reaction with the foil, but they are also mild abrasives, and therefor excellent for cleaning. You can make an inexpensive scouring powder with equal parts coarse salt, baking soda, and borax [affil links]. (Works wonders on ceramic stove tops.)

For cleaning brass or bronze, try this formula. I use this solution for my bathroom cleaner and it?s simply amazing. Just spray, let sit a few minutes, wipe and rinse. Soap scum, hard water build up, and any kind of "crusties" will start to disappear in just a few days; and it leaves your fixtures bright and shiny. For gunked-up shower heads, just spray and leave. We've also used this for burnt pans, grill grates, car bumpers, and all kinds of outside surfaces.
1 c. white vinegar [in bulk on eBay or Amazon] (dissolves soap scum)
2 T borax (scouring agent)
2 T lemon or lime juice (polishes/makes shiny)
1/4 tsp. bleach [adv: bleach/sodium hypochlorite in bulk on eBay or Amazon] (cleans/disinfects surfaces)
1 c. water

A. Hi Leslie. You should lay the plate under the punch bowl, with the bowl fully submerged in a large plastic dishpan or a fiberglass or Corian sink (not a conductive metal sink). I can't countermand the instructions that came with the cleaning plate, but I'm sure you're supposed to rinse it. Good luck.

Regards,