Thursday, September 08, 2011

Polishing silver with chemistry

I am not a chemist, not by a long shot. But I am lazy, and Stacy found a method online for polishing silver which required very little manual effort. See here. Basically, you put the silver in contact with some aluminum foil, pour on boiling water with lots of baking soda dissolved, and wait. According to that site, "In the reaction, sulfur atoms are transferred from silver to aluminum, freeing the silver metal and forming aluminum sulfide." Sounds like chemistry to me, but could be technobabble for all I know. So, being somewhat skeptical of many save-effort suggestions online, I checked with a chemist (thanks, notElon!) who said it should work, but suggested scuffing up the aluminum to help strip off the oxide coating.

With his endorsement, I set out to polish an heirloom pie server thing. Here it is in a pot lined with aluminum foil:

I boiled water, mixed in the baking soda, poured it on, and behold! A reaction!

Unsuprisingly, it smelled like sulfur (I assume that's the aluminum sulfide). Here's a video where you can see the bubbling and hear me commenting on the smell (in case you don't trust written-word Eli), and feel free to click-through to full-size:

In any case, it did a pretty good job and I'd do it again next time. Hooray for chemistry!

1 comment:

  1. Thanks for the name drop.

    The reason it smelled of sulfur is that unlike silver sulfide, aluminum sulfide is unstable with respect to the hydroxide. So there is actually a second reaction that goes on at a slower timescale, turning the newly formed aluminum sulfide and water to aluminum hydroxide and hydrogen sulfide.