First, can fingernails scratch concrete walls? Jewish mythology says yes. Science says no.
Dario Gabbai, a former Jewish prisoner of Auschwitz said: “They were screaming—all the people, you know—they didn’t know what to do, scratching the walls, crying until the gas took effect. If I close my eyes, the only thing I see is standing up—women with children in, in their hands, there.”
In 1822 the German mineralogist Fredriech Mohs developed a “scratch test” used to determine mineral hardness. He developed a hardness scale that helps to identify mineral properties. The scale measures hardness on a scale of 1-10. One being the softest mineral (talc) and 10 being the hardest mineral (diamond). Common objects of known hardness can be used to determine mineral hardness. These common objects are: your fingernail (2.5), a penny (3), a piece of glass (6) and a knife blade or nail. For example, if your fingernail can scratch the mineral, it has a hardness of less than 2.5, which is quite soft. If the mineral can scratch glass it has a hardness of greater than 6, which is very hard.
The Mohs hardness scale is still frequently used today.
Fingernail’s Mohs hardness = 2.5 (some sources say 2.2)
Concrete’s Mohs hardness = 5 to 9 (depend on the type of concrete)
So fingernails can’t leave marks in concrete when scratching it. If concrete is scratched by fingernails, only a fingernail powder will be left on the scratched concrete surface (but no furrow) because fingernails are softer than concrete. In other words, if the jewish story tellers want us to believe their tales, they will have to make us believe that fingernails are harder than concrete.
Source / Credits
Comment author is hermie on the Scrapbookpages Blog, in a post titled “Proof that the dying victims inside the Auschwitz gas chamber scratched the walls with their fingernails”.