# How does foil, baking soda and hot water clean silver? **URL:** \ **Category:** Factual Questions\ **Created:** [January 7, 2012, 8:10pm UTC](https://boards.straightdope.com/t/how-does-foil-baking-soda-and-hot-water-clean-silver/608757 "2012-01-07T20:10:55Z")\ **Posts on this page:** 20\ **Page:** 1
**Author:** ![Sri\_Theo](https://avatars.discourse-cdn.com/v4/letter/s/f04885/32.png) [@Sri\_Theo](https://boards.straightdope.com/u/Sri_Theo)\ **Post date:** [January 7, 2012, 8:10pm UTC](https://boards.straightdope.com/t/how-does-foil-baking-soda-and-hot-water-clean-silver/608757/1 "2012-01-07T20:10:55Z")
So I recently had need to clean some silver, and [this technique](http://www.youtube.com/watch?v=CsKLcc13WBo) was shown to me. Basically you put hot water, baking soda and foil in a bowl. Add the silver and tarnish disappears in under a minute. Can anyone explain to me what, chemically speaking, is happening here? Otherwise I’m going with witchcraft. ---
**Author:** ![aceplace57](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/aceplace57/32/3500_2.png) [@aceplace57](https://boards.straightdope.com/u/aceplace57)\ **Post date:** [January 7, 2012, 8:20pm UTC](https://boards.straightdope.com/t/how-does-foil-baking-soda-and-hot-water-clean-silver/608757/2 "2012-01-07T20:20:01Z")
Did it produce a smelling gas? I think you should get hydrogen sulphide from this reaction. Baking soda is NaHCO3, Aluminum AL Silver Ag My chemistry is too rusty to do the equation for you. ---
**Author:** ![Nametag](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/nametag/32/406_2.png) [@Nametag](https://boards.straightdope.com/u/Nametag)\ **Post date:** [January 7, 2012, 8:27pm UTC](https://boards.straightdope.com/t/how-does-foil-baking-soda-and-hot-water-clean-silver/608757/3 "2012-01-07T20:27:25Z")
Electrolysis. The silver, aluminum, and bicarbonate solution act as a battery, with the aluminum donating electrons to the silver. Aluminum is highly electronegative, and silver is highly electropositive, so the reaction occurs quite readily. ---
**Author:** ![Canadjun](https://avatars.discourse-cdn.com/v4/letter/c/76d3ee/32.png) [@Canadjun](https://boards.straightdope.com/u/Canadjun)\ **Post date:** [January 7, 2012, 8:41pm UTC](https://boards.straightdope.com/t/how-does-foil-baking-soda-and-hot-water-clean-silver/608757/4 "2012-01-07T20:41:43Z")
> [@aceplace57](#): > > Did it produce a smelling gas? I think you should get hydrogen sulphide from this reaction. > > Baking soda is NaHCO3, Aluminum AL Silver Ag > > My chemistry is too rusty to do the equation for you. Hmm… I don’t see any sulfur in there. ---
**Author:** ![Sigene](https://avatars.discourse-cdn.com/v4/letter/s/df788c/32.png) [@Sigene](https://boards.straightdope.com/u/Sigene)\ **Post date:** [January 7, 2012, 8:44pm UTC](https://boards.straightdope.com/t/how-does-foil-baking-soda-and-hot-water-clean-silver/608757/5 "2012-01-07T20:44:03Z")
the tarnish is silver sulfide sulfur comes from the tarnish ---
**Author:** ![johnpost](https://avatars.discourse-cdn.com/v4/letter/j/f17d59/32.png) [@johnpost](https://boards.straightdope.com/u/johnpost)\ **Post date:** [January 7, 2012, 9:15pm UTC](https://boards.straightdope.com/t/how-does-foil-baking-soda-and-hot-water-clean-silver/608757/6 "2012-01-07T21:15:37Z")
clean the silver when you want it shiny for use or looks. the tarnish is not destructive to the metal. ---
**Author:** ![Dufus](https://avatars.discourse-cdn.com/v4/letter/d/c77e96/32.png) [@Dufus](https://boards.straightdope.com/u/Dufus)\ **Post date:** [January 7, 2012, 11:57pm UTC](https://boards.straightdope.com/t/how-does-foil-baking-soda-and-hot-water-clean-silver/608757/7 "2012-01-07T23:57:22Z")
Wouldn’t the tarnish be silver oxide? ---
**Author:** ![aceplace57](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/aceplace57/32/3500_2.png) [@aceplace57](https://boards.straightdope.com/u/aceplace57)\ **Post date:** [January 8, 2012, 12:26am UTC](https://boards.straightdope.com/t/how-does-foil-baking-soda-and-hot-water-clean-silver/608757/8 "2012-01-08T00:26:49Z")
There’s a theory that silver didn’t tarnish as badly in the pre-industrial age. There’s more sulfur in the air and causes more tarnishing. Cecil disagrees about the extra sulfur in the air. > **[Unshiny day: Is there more sulfur in the air than in preindustrial times? Is...](https://www.straightdope.com/21343493/unshiny-day-is-there-more-sulfur-in-the-air-than-in-preindustrial-times-is-this-making-silver-tarnis)** > [@](#): > > Silver sulfide, Ag2S, is the sulfide of silver. This dense black solid constitutes the tarnish that forms over time on silverware and other silver objects > **[Silver sulfide](https://en.wikipedia.org/wiki/Silver_sulfide)** > > Silver sulfide is an inorganic compound with the formula Ag2S. A dense black solid, it is the only sulfide of silver. It is useful as a photosensitizer in photography. It constitutes the tarnish that forms over time on silverware and other silver objects. Silver sulfide is insoluble in most solvents, but is degraded by strong acids. Silver sulfide is a network solid made up of silver (electronegativity of 1.98) and sulfur (electronegativity of 2.58) where the bonds have low ionic character (appr... ---
**Author:** ![Sri\_Theo](https://avatars.discourse-cdn.com/v4/letter/s/f04885/32.png) [@Sri\_Theo](https://boards.straightdope.com/u/Sri_Theo)\ **Post date:** [January 8, 2012, 6:15pm UTC](https://boards.straightdope.com/t/how-does-foil-baking-soda-and-hot-water-clean-silver/608757/9 "2012-01-08T18:15:34Z")
So the tarnish is either silver sulfide or silver oxide? Does the tarnish de-oxidise somehow returning it to normal silver? (Yes there was a nasty smell). So this method is actually better than polishing which removes a layer of silver? Thanks for the answers. ---
**Author:** ![johnpost](https://avatars.discourse-cdn.com/v4/letter/j/f17d59/32.png) [@johnpost](https://boards.straightdope.com/u/johnpost)\ **Post date:** [January 8, 2012, 6:43pm UTC](https://boards.straightdope.com/t/how-does-foil-baking-soda-and-hot-water-clean-silver/608757/10 "2012-01-08T18:43:09Z")
both silver sulfide and silver oxide are black. tarnish is silver sulfide. this method changes the silver sulfide back to silver. this method is easier and better than polishing which removes some of the material (which could be turned back to silver). ---
**Author:** ![GaryM](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/garym/32/241_2.png) [@GaryM](https://boards.straightdope.com/u/GaryM)\ **Post date:** [January 9, 2012, 3:25am UTC](https://boards.straightdope.com/t/how-does-foil-baking-soda-and-hot-water-clean-silver/608757/11 "2012-01-09T03:25:31Z")
In my experience with using this method I’ve found that removing the tarnish is not the same as polishing. The object may not be shiny, but won’t be tarnished. ---
**Author:** ![Mangetout](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/mangetout/32/19_2.png) [@Mangetout](https://boards.straightdope.com/u/Mangetout)\ **Post date:** [January 9, 2012, 7:18am UTC](https://boards.straightdope.com/t/how-does-foil-baking-soda-and-hot-water-clean-silver/608757/12 "2012-01-09T07:18:42Z")
In my experience, this method leaves the silver bright, but not shiny. The surface is rendered slightly rough or matt. I strongly disadvise doing this to any piece you care about. ---
**Author:** ![spotthegerbil](https://avatars.discourse-cdn.com/v4/letter/s/439d5e/32.png) [@spotthegerbil](https://boards.straightdope.com/u/spotthegerbil)\ **Post date:** [January 9, 2012, 10:39am UTC](https://boards.straightdope.com/t/how-does-foil-baking-soda-and-hot-water-clean-silver/608757/13 "2012-01-09T10:39:30Z")
We both have slver wedding rings, as we don’t like the colour of gold. Mrs G’s ring was looking a little tarnished, so, following my mothers advice, we mixed up a cup of biological soap powder and some water, and left the ring over night. Big mistake. Very big mistake. Next morning the ring was completely black. In thinking about mums advice, she only had gold jewellery, so it’s never going to tarnish, and the gunk in the powder didn’t have an effect. After a small panic, we bought a jewellery bath from a local jewellers, and with the help of a polishing cloth, the ring came up very nice. The ingredient in the bath was a urea compound. Listen to your mother, but be selective which advice you follow. ---
**Author:** ![johnpost](https://avatars.discourse-cdn.com/v4/letter/j/f17d59/32.png) [@johnpost](https://boards.straightdope.com/u/johnpost)\ **Post date:** [January 9, 2012, 2:25pm UTC](https://boards.straightdope.com/t/how-does-foil-baking-soda-and-hot-water-clean-silver/608757/14 "2012-01-09T14:25:14Z")
chemical reversal of the tarnish has the advantage of not loosing any metal, happens quickly and without physical effort. if you has something with lots of crevices then it would take a long time to remove thetarnish and you risk damaging the object physically trying to scrape in those areas. you don’t get a mirror finish. chemical methods and physical methods each have their advantages. ---
**Author:** ![Hari\_Seldon](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/hari_seldon/32/5173_2.png) [@Hari\_Seldon](https://boards.straightdope.com/u/Hari_Seldon)\ **Post date:** [January 9, 2012, 9:14pm UTC](https://boards.straightdope.com/t/how-does-foil-baking-soda-and-hot-water-clean-silver/608757/15 "2012-01-09T21:14:21Z")
Basically, silver is less reactive than aluminum. I am not sure of the valences involved, but the primary reaction is that silver sulfide + aluminum —\> silver + aluminum sulfide. I see no reason why it wouldn’t also reduce silver oxide. I would assume (but I might be wrong about this) that the main function of the bicarbonate is to increase electrical conductivity, but I guess there is some reaction with it as there is some hydrogen sulfide being given off. Yes, it does produce a matte finish. But you don’t lose the silver. For solid silver, this might not matter too much, but if you keep polishing silver plate you will eventually wear it down to the base metal. ---
**Author:** ![Chronos](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/chronos/32/134_2.png) [@Chronos](https://boards.straightdope.com/u/Chronos)\ **Post date:** [January 9, 2012, 10:37pm UTC](https://boards.straightdope.com/t/how-does-foil-baking-soda-and-hot-water-clean-silver/608757/16 "2012-01-09T22:37:23Z")
You could probably also use some combination of polishing and electrolyzing to get a good compromise between losing material and matting. ---
**Author:** ![Mangetout](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/mangetout/32/19_2.png) [@Mangetout](https://boards.straightdope.com/u/Mangetout)\ **Post date:** [January 10, 2012, 2:19am UTC](https://boards.straightdope.com/t/how-does-foil-baking-soda-and-hot-water-clean-silver/608757/17 "2012-01-10T02:19:33Z")
Can someone provide a citation on the claim that none of the metal is lost in this process? I accept that the chemical reaction of tarnishing is being reversed in this process, but is it guaranteed that the restored silver is remaining on the piece? (rather than, say, remaining in suspension in the bath) Is the matt surface the result of replating? ---
**Author:** ![VOW](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/vow/32/3043_2.png) [@VOW](https://boards.straightdope.com/u/VOW)\ **Post date:** [January 10, 2012, 2:24am UTC](https://boards.straightdope.com/t/how-does-foil-baking-soda-and-hot-water-clean-silver/608757/18 "2012-01-10T02:24:56Z")
Hmmm. The way I understand it, the oxidation of the silver means the single molecule layer on the surface of the silver is already GONE, removed from the metallic silver. Cleaning the silver, either by this chemical reaction or by polishing, is simply removing the oxidized layer. Think of rust on the surface of iron. The part of the iron which has reacted and turned into rust is GONE from the metallic iron. No matter how you clean the rusted part off, you cannot salvage any of the iron which has been transformed into rust by oxidation. ~VOW ---
**Author:** ![Mangetout](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/mangetout/32/19_2.png) [@Mangetout](https://boards.straightdope.com/u/Mangetout)\ **Post date:** [January 10, 2012, 2:41am UTC](https://boards.straightdope.com/t/how-does-foil-baking-soda-and-hot-water-clean-silver/608757/19 "2012-01-10T02:41:29Z")
> [@VOW](#): > > Hmmm. The way I understand it, the oxidation of the silver means the single molecule layer on the surface of the silver is already GONE, removed from the metallic silver. Cleaning the silver, either by this chemical reaction or by polishing, is simply removing the oxidized layer. > > Think of rust on the surface of iron. The part of the iron which has reacted and turned into rust is GONE from the metallic iron. No matter how you clean the rusted part off, you cannot salvage any of the iron which has been transformed into rust by oxidation. > ~VOW Sure you can - oxidation is (in general) a reversible chemical reaction. I’m just not certain that the products of that reverse reaction truly do end up back on the item being cleaned. ---
**Author:** ![johnpost](https://avatars.discourse-cdn.com/v4/letter/j/f17d59/32.png) [@johnpost](https://boards.straightdope.com/u/johnpost)\ **Post date:** [January 10, 2012, 2:44am UTC](https://boards.straightdope.com/t/how-does-foil-baking-soda-and-hot-water-clean-silver/608757/20 "2012-01-10T02:44:02Z")
chemical reactions like this are reversible. sulfides and oxides that remain attached to the bulk metal can become the metal again through a chemical reaction. [Next page](https://boards.straightdope.com/t/how-does-foil-baking-soda-and-hot-water-clean-silver/608757.md?page=2)