Just how do suction cups suck?

 Imagine that everything and everybody on earth is completely surrounded by an ocean of air, which puts pressure on both the inside and outside of everything. When you press a suction cup against a wall or window, you push out the air inside it, eliminating the pressure inside the suction cup and creating a vacuum which seals the cup tightly to the surface you want it to stick to. A suction cup will come off when the air pressure on the outside becomes lower than the air pressure inside the suction cup. You’ll hear a “pop” sound when you pull a suction cup off the wall…that’s the air rushing in to fill the vacuum.

Modern suction cups are made of highly flexible synthetic materials such as PVC plastic or neoprene. Prized for their pliability, these materials are preferred to natural rubber because they are stronger and more resistant to sunlight, abrasion and temperature extremes. Earlier suction cups were made of natural rubber, and the very first suction cups were made of glass or gourds.

These handy devices are designed to conform to the shape of the surface that they are stuck to, and will adhere best to surfaces that are smooth and non-porous, like metal or glass.

Now, here’s a stunning example of the holding power of suction cups!

Back in the 1600’s, a talented German engineer named Otto van Guericke decided to pit the power of the vacuum against the strength of 16 strong horses…and won. 

Van Guericke had a hollow copper ball manufactured and then cut in half. Using a very clever pump of his own design, Guericke placed the two halves together and removed most of the air inside them.

Then, he gathered all the townspeople together and hitched two teams of horses to both halves of the copper ball. No matter how hard the horses pulled, the two copper halves wouldn’t separate. Then, in front of his dumbfounded audience, van Guericke pulled a plug allowing the air back inside, and the two halves fell apart with a simple touch.

Of course, van Guericke’s suction cups had a lot of help from our thick atmosphere which squeezed both halves together like a vise—entirely unopposed by any pressure on the inside.

Now that you know what makes suction cups suck, click onto Uses for Suction Cups to learn about what you can use them for…from the funny to the familiar, you’ll find suction cups almost everywhere you go! Or, click onto Tips on Using Suction Cups to find out how they’ll keep on working…and working…and working!