Sharpening Scissors with aluminium foil There are lots of websites 1, 2,3 that claim you can sharpen scissors by cutting aluminium foil. Does this work? What would be the cause of this? 
 A: It might work to some degree, but not by sharpening.
There has been speculation about a way for the foil to sharpen a blade: The foil is coated by a thin film of aluminum oxide (Al$_2$O$_3$), which happens to be a known abrasive and, thus,

the aluminum oxide layer on the foil acts and an abrasive and there might be some sharpening effect.

The main problem with this idea, besides the tiny amount of oxide found in the nanometer-thick layer, is probably that the oxide is abrasive in its crystalline form, while the thin film of Al$_2$O$_3$ is amorphous (from what I gather from the literature, e.g., papers 1, 2, 3, 4).
Nonetheless, anecdotal evidence is divided on the efficacy of the method (see, e.g., forums 1 and 2). This can be explained by the subjectivity of the reported observations, as well as by confounding factors, such as 1) different types/quality of scissors (e.g., some cut mostly by shearing), 2) initial degree of dullness, and 3) effects other than sharpening that affect how well the scissors cut.
For instance, the perceived improvement might result from:


*

*removal of burrs (smoothing the edge)

*steeling (straightening the edge)

*simple cleaning


Note: there is an older question on that in the Skeptics SE.
A: The substance on the sharpening surface must be harder (hardness is measured on the Mohs scale) than the material being sharpened; diamond is extremely hard, making diamond dust very effective for sharpening.
Moh's hardness scale of metals gives the following values for steel(alloy generally used to make scissors) and aluminium:
Steel:4.0
aluminium: 2.75
Since aluminium appears to be lower in rank compared to steel I don't think that sharpening scissors with aluminium is effective.
References:
https://en.wikipedia.org/wiki/Sharpening#Tools_and_materials_for_sharpening
https://www.alansfactoryoutlet.com/the-hardness-of-metals-a-visual-representation-of-mohs-scale
