Orgone Research

Saturday, November 11, 2006

Just Beat It

From time to time, my mother would encounter a glass jar with its lid stuck on. Her reaction would be to bang the lid onto the stainless steel counter top in our kitchen. As I moved through childhood, I eventually encountered that classic "scientific" household tip; run the metal jar lid under hot water. This was claimed to be "scientific", as it was claimed to be based on the principle of differential expansion; the metal would expand more than the glass, and so would result in a greater spatial tolerence between the metal and the glass.

While it's clear by sheer empirical proof that this technique works, I began to doubt the claimed reason several years ago. After I became something of a gearhead I became rather obsessed with threaded fasteners. This was partly due to reading a really wonderfull book entitled Engineer to Win by Carroll Smith.

Smith discussed how threaded fasteners stay fastened. One classic way is to use a a "thread locker" like Loctite. Good enough, but what do you do when when you want to remove the fastener? According to Smith, you use heat. Heat lowers the viscosity of the thread locker chemical, and vastly lowers the torque required to unscrew the fastener.

Suddenly it dawned on me, that's how the old stuck-jar-lid trick works as well; it's probably not due to something as exotic as differential expansion, but simply to lowering the viscosity of the thick food substance caught in the threads! Think about it, jar lids are not usually stuck when they are unopened, they get stuck after you pour out the food substance. Further, they are usually stuck when they are kept in the refrigerator, increasing the viscosity of the food stuck in the threads!

Though I believed the commonly held explanation of "differential expansion" as a child, I was correct in believing that heating the jar lid with hot water is the correct technique to remove it. I remember telling my mother this, and further suggesting that her banging of the jar lid was counterproductive, in that it would tend to cause the threads to bend and distort, and make things worse. Sadly, my mother was a fundamentally irrational person, and continued to bang away at those stuck jar lids. She went to her death believing that was the way to do it.


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