Why do metal shavings stick to the eye?

April 21, 2013 10:19 AM

My understanding is that things like sand or sawdust wash out of the eye easily but things like metal shavings especially steel shavings tend to stick to the eye and wont wash out. Why is this?
posted by john123357 to Health & Fitness (7 answers total)

Metal shavings are SHARP and tend to stick into the eye, rather than sit on the surface.
posted by mollymayhem at 10:29 AM on April 21, 2013 [1 favorite]

Response by poster: other things can be sharp as well like some sawdust or small splinters but it seems they come out easier
posted by john123357 at 10:32 AM on April 21, 2013

sawdust and splinters are an incredibly different kind of sharp -- think about how well you're going to be able to slice a tomato (or cut a steak) with a wooden knife.
posted by KathrynT at 10:33 AM on April 21, 2013

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posted by LobsterMitten (staff) at 10:35 AM on April 21, 2013

Metal shards have a much sharper edge than stone or wood, and are usually harder material. Wood, for example, softens immediately on touching the fluid on your eye. They also tend to be heavier, so will impact the eye more solidly and be less likely to be deflected by simple things like tears.

Additionally, metal shards are incredibly jagged and barbed. Compare a metal shaving to a wood shaving and sand under a microscope. The points on a splinter of wood will have the points aligned in one direction, making it easy to pull out. Sand doesn't have jagged points (it's the product of erosion after all, all the sharp bits have been worn off. Metal shards, on the other hand, are like balls of tiny industrial fishhooks, curved pointy bits sticking out in all directions. Once it gets more than one barb in you you can't pull it straight out without tearing something.

There might also be an evolutionary component. Creatures have been getting sand in their eyes since they had eyes, and have evolved ways to deal with it. Metal hasn't been popular until recently (evolutionarily speaking), and even then, most people go their whole lives without encountering shards of it in their eyeballs.
posted by Ookseer at 10:45 AM on April 21, 2013 [1 favorite]

My father worked many years constructing metal grain bins in the midwest and would at times get a metal shaving in his eye. They actually do embed themselves in your eye (unlike wooden splinters) and the first time this happened he went to the doctor where they "froze" his eye and pulled the shaving out.

Once he was tired of paying the doctor to do the procedure, he pulled them out himself with a tweezer, leaving a rust ring in his eye for several days. (This is not recommended....)
posted by drewski at 11:52 AM on April 22, 2013

Response by poster: Broken glass pieces are extremely sharp, do they stick to the eye as much as metal shavings?
posted by john123357 at 12:09 AM on April 29, 2013