Monday, November 12, 2012

some actual science, sort of

Last year I got a thin rubberized-skin type of phone cover for my then relatively new phone.  When I got it, it fit like a proverbial glove, but after a few months it started to get loose.  It was only loose by a millimeter or so, but it was enough to be irritating almost every time I touched the phone.  It would shift and gave the phone a slightly vague feeling in my hand.

it's difficult to see, but the entire 'bezel' of the case is standing slightly proud of the face of the phone

this shot shows the gap in the bezel more clearly, look at the dark gap next to the power button, where there should be no room at all

here the gap around the perimeter is exemplified by the dark gap next to the power button

scintillating view of the gap behind the bezel

So, hopefully, you are asking "WTF is he whining for?" The thing about this that struck me at the time was that it reminded me of a specific experience I had in the lab on a number of occasions.

Several of the labs I worked in used IKA stir plates.  IKA plates are awesome, except for one significant drawback, the bodies are plastic, and susceptible to a number of common lab chemicals.  The last lab I worked in had clear silicone rubber covers for the bodies of the plates to protect them from small splashes.  Of course the most common thing to get splashed on the covers is oil from oil baths.  Like a lot of chemists I despise how oil gets everywhere, and I was always waging a battle against oil contamination and cleaning oil off of every surface and piece of glassware that entered my hood.  Similarly irritating was the fact that the silicone covers would swell and distort when oil got on them, and they eventually would fit so poorly that they would interfere with access to the controls.  With my hatred of oil contamination verging on obsessive compulsive disorder, I would periodically clean my covers to ameliorate this.  A quick rinse with water, then acetone, then a nice soak in hexanes always removed the oil nicely.

The distorted phone cover reminded me of the distorted stir plate cover, and I guessed the the phone cover distortion  may have come from skin oils and hand lotion.  If I could remove it, the cover should go back to normal.  I assumed that the material(s) that absorbed were non-polar, because I assume that the material is silicone which would absorb polar things poorly.  In any case an experimental soak would do no damage if the cover was the other likely material, polyurethane.

Not being a lab chemist anymore, I don't have ready access to hexanes any more, so I used white gas.  White gas is similar in solvent properties to hexane, and I've used it in the home shop before to clean things hat I would have otherwise used hexanes for.  As an extra added bonus, when silicone is soaked in non-polar solvents it swells up like someone with a peanut allergy in a Thai restaurant.  It's a little disconcerting the first time you see it, the first thought I had, years ago, was "Oh shit, I ruined it!"

after about a day's soak it pretty much fills up a peanut jar

When I first took it out of the white gas, the phone cover was grossly oversized like a clown shoe, which is exactly what I wanted to see.


After I let the phone cover sit out and off-gas for a day or so it fit the phone much better than before.  Was it perfect again?  Not even close, but it was a significant improvement over the prior looseness.  Interestingly, it had a slight kerosene or diesel smell for a week or two after.  I think this is an issue with the white gas that wouldn't be seen with hexanes.  Hexanes are pretty pure, but the white gas is not as clean a distillate.  Presumably the white gas has some heavier alkanes in it (like kerosene and diesel) that take longer to evaporate out of the material due to the higher boiling points.  Eventually it all evaporated out, and wasn't much of an issue.

At this point, all excited with my own ingenuity, I thought I might fix a similar problem with my much beloved pen.
video
loosy goosey

After the same treatment I was rewarded with another grossly oversized component.



Unfortunately once it dried, the pen grip shrunk to significantly smaller than the original size, and feels like plastic.  I had to lubricate it with water just to be able to re-install it.  At this point the pen is pretty much only there for memories, and doesn't get used any more.

seems like there should be some sort of penis joke here

The moral of the story, obviously, is only try this on things that you can afford to accidentally destroy.

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