I have my late grandpa's silver spoon attached to my fridge with a neodymium magnet. What kind of chemical reaction causes that discolouration?
this post was submitted on 15 Feb 2026
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https://en.wikipedia.org/wiki/Tarnish
...galvanic reaction in this case, accelerated oxidation from contact between differential metals...
Thanks for the link.
That just doesn't explain the reaction between the two metals.
Somehow the silver got colourful instead of the usual grey.
I recall reading something about titanium and its color. The thickness of the surface layer determines the color. It’s just nanometers thick, but that means light begins to do weird stuff at that scale. I suspect the same applies to the silver oxide/sulfide/whatever layer on the spoon. If that’s the case, you’re not actually seeing the color of the surface layer. The layer is exactly the right thickness that specific wavelengths of light get reflected back while others don’t.
Proper physicists can add more details.
Thin film interference
Thanks!
Based on the phase interaction part of the article, there’s constructive and reconstructive phase interaction going on. That chapter has some nice diagrams about it.
That’s what produces the different colors. The thickness of the layer determines which wavelengths are lucky enough to reflect this way.
Also, here’s what happens with iron oxide.
There are multiple examples of the colorful toning in the article I linked. So you appreciated the link, but not enough ot actually look through it.
Pictures of tungsten tarnishing aren't helpful when op is talking about silver. Stating "thank you, that's the general idea yes, but I was trying to ask more specifically" isn't an attack on you. You don't need to defend yourself.
Right below the picture of tungsten is this picture of a silver dollar.
That is a surprisingly not blue tarnish, if its supposed to explain what OP is showing us, if it makes a point, please help me comprehend.
I do see that the light has mostly obscured a small band of blue so maybe its at a really neat phase of tarnish, but that's speculation and this photo provides no evidence that is actually the case. Either way, I really dont think the tarnish article goes far to actually explain the blue aside from describing the mechanism.
Reading comprehension... What even is it?
You sandwiched your admission that the photo showed blue tarnish on silver between a claim that the photo didn't show blue and the false claim that the OP specifically asked why blue in particular.
Your post started with "pictures of tungsten aren't helpful". This is proof you didn't read the Wikipedia article where it shows a silver coin with tarnish.
The OP didn't say blue. They said colorful. You brought up blue to deflect from you not reading the article that showed colorful silver tarnish.
I read everything. (Even changed to my mother tongue.)
Didn't find anything about interactions of different metals. It only said something about interactions of metals and non-metals.