Suction Cups 101
8 Tips on Using Suction Cups
The care and use of suction cups is very simple.
- Make sure the suction cup is clean and free from debris.
- If the suction cup needs to be cleaned, wash in warm soapy water then dry gently with a lint-free cloth.
- Clean the surface you are applying the suction cup to. It won’t adhere well to a dirty surface.
- To enhance suction, a tiny dab of Vaseline or cooking oil may be rubbed on the rim of the cup.
- Press the cup all the way down, against the surface.
- The suction cup may need to be “burped” periodically by pressing down on it to remove any air that may have seeped in.
- Temperature and humidity variations may make a suction cup lose its grip. If bonded above 40⁰ F/5⁰ C the cup will provide the most reliable service from -22⁰ to 120⁰ F.
- To remove the cup, simply pull up on the release tab to break the suction.
The Science on How a Suction Cup Works
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.
In scientific terms, gravity and friction are the two main forces that make it possible for suction cups to work. Gravity pulls the molecules in the air toward earth, creating atmospheric pressure of roughly 14.7 pounds per square inch at sea level. A good cup on a slick surface causes that pressure to be applied to the outside of the cup, pushing it down onto the surface. Friction keeps the cup from sliding.
To calculate the force of a suction cup, use the formula
F = AP where F = force, A = area, P = pressure.
This is derived from the definition of pressure, which is
P = F/A
For example, a suction cup of radius 2.0 cm has an area of (0.020 m)2 = 0.0013 square meters. Using the force formula (F = AP), the result is F = (0.0013 m2)(100,000 Pa) = about 130 newtons, assuming the pressure inside the suction cup is negligible when compared to atmospheric pressure (about 101,000 Pa). 
Modern suction cups are made of highly flexible synthetic materials such as PVC plastic or neoprene. Prized for their reliability, 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.
The History and Patents of Suction Cups
First Documented Usage of the Suction Cup
As far back as third century B.C., the suction cup was more important to the practice of medicine than the stethoscope is today. Suction cups made out of gourds, were attached to the skin and supposedly drew bad blood away from diseased organs to the surface of the body. The procedure, believed to have been invented by Hippocrates the first medical doctor, was called “cupping.” It was used to cure a wide range of illnesses. 
Suction Cup Patents Date Back to the Mid-1800s
The first modern suction cup patents were issued by the United States Patent and Trademark Office during the 1860s. TC Roche was awarded U.S. Patent No. 52,748 in 1866 for a "Photographic Developer Dipping Stick." The patent discloses a primitive suction cup meant for handling photographic plates during developing procedures. In 1868 Orwell Needham patented a more refined suction cup design, U.S. Patent No. 82,629, calling his invention an "Atmospheric Knob." Its purpose was for general usage -as a handle and drawer opening means. 
- Photographic Developer Dipping Stick (1866) 
- Atmospheric Knob (1868) 
- Device For Holding Letters (1882) 
- Vacuum Hook (1889) 
- Bosom Form (1889) 
- Projectile (1903) 
- Nursing Attachment (1910) 
- Combined Force Cup and Cleaner (1915) 
- Dart (1926) 
- Wind Operated Toy and Mounting (1927) 
- Suction Cup Rattle (1950) 
- Toy Missile (1961) 
- Suction Cup for Use in Windows (1991) 
Photographic Developer Dipping Stick
Patented February 20, 1866 by T.C. Roche
A new and improved developing stick with a suction pad of India rubber at one end which can raise a glass plate or other material and hold it in the proper position for applying developing solution. With the advent of this invention, it was no longer necessary to handle the plate or soil the fingers with solution. 
Patented September 29, 1868 by Orwell H. Needham
A knob or handle, applicable to opening drawers or doors, in which not only the suction plate or face of the handle is made of rubber or other suitable flexible material, but in which the knob portion of the handle is also flexible or elastic and made of the same piece as the sucker portion. This allowed stronger suction, creating a strong, direct pull on the object to be opened without destroying the shape of the handle. 
Device for Holding Letters, Cards, Photographs, etc.
Patented February 7, 1882 by W. H. Jones and C. L. Middleton
The first truly modern retail display technique. This adhesive device holds and supports letters, cards, photographs and similar articles. Ideal for hanging light goods or other materials in showcases, or for the purpose of holding articles used in decorating store windows, and for holding rods for that and for other purposes. Also as a toy for lifting weights, consisting of a concave rubber cup with a cap and clip-spring regulated by a screw-knob and rod or bar to hold the desired objects. 
Patented February 26, 1889 by F. White
From caps to coats, it keeps all your hang-ups handy! A metal hook projecting from the convex side of a cup or holder made of yielding elastic material such as India rubber which can be secured to a smooth, airtight surface using atmospheric pressure. 
Patented April 9, 1889 by J. W. Greene
A breast form and suction cup consisting of a compressible spring-frame and elastic rubber cup which can be compressed against the breast for the purpose of developing and enlarging it. When not used as a suction cup, the form may be worn as a bosom form held in place by a corset…until such time as the breast is sufficiently enlarged that the form no longer needs to be used. 
Patented August 4, 1903 by G. Schrodel
An improved projectile to be used as an arrow or dart, which will carry a small, cup-shaped elastic disk or plate to the target and cause the plate to adhere to the target. Completely harmless to children and animals, it will adhere to angles or corners and to soft, concave, convex or other surfaces. 
Patented by H. B. Cunningham, February 15, 1910
The nursing attachment was designed to “avoid unpleasant and embarrassing situations in which mothers are sometimes placed in public places by the necessary exposure of the breast in suckling.” Worn underneath the blouse, the device, comprised of a breast shield, suction cup with threaded stem, a tube and a nursing nipple, allowed the mother to slip the nipple out for feeding without exposing her own breast. 
Combined Force Cup and Cleaner
Patented February 23, 1915 by L.O. Howell
An early toilet plunger/cleaner making use of simple suction cup technology. 
Patented October 5, 1926 by N.E. Samsel
A game device, comprising a body portion and an integral tail portion, spaced apart fins on the free end of the tail, a rubber vacuum cup integral with the body, and a longitudinal tube within the body, as a means to regulate the passage of air through the tube. When thrown, the devise will adhere to the target object by creating a suction which will hold until it is released by the thrower. 
Wind Operated Toy and Mounting
Patented October 18, 1927 by E. Ischinger
A wind-operated toy and mounting which can be attached to a flat surface such as a windshield, head light or other portion of an automobile to be operated by the air current created by the movement of the car or by the wind when the car is standing still. The toy is comprised of a pinwheel-like device attached to a shaft and rubber suction cup. 
Suction Cup Rattle
Patented December 5, 1950 by B. Gelardin
A child’s toy which mounts securely with a suction cup to high chair tray or table top, allowing a baby to push and wobble the clown figure without knocking it to the floor. 
Patented March 28, 1961 by L.C. Crisci
A trigger operated toy aircraft which can be released either from the hand or from a holder in the hand or on the ground. The nose of the aircraft is equipped with a suction cup for playing dart type games, with an added benefit of protecting furniture, mirrors or other delicate and fragile objects. 
Suction Cup for Use in Windows, (Light Diffusing Rings)
Patented August 13, 1991
by William E. Adams (Adams Manufacturing)
Previously existing suction cups tended to focus light like a magnifying glass, resulting in scorched surfaces and color fading. After years of extensive R&D and testing, Adams Manufacturing invented a groundbreaking new way to overcome this serious product limitation using what they called Light Diffusing Rings. This trademarked technology eliminates the hot light focal points that are generated in intense sunlight—often causing damage to plastic, vinyl or textile interiors. To this day, Adams Manufacturing continues to integrate this cutting-edge technology into all of their suction cups. 
- Wikipedia: Suction Cup
- United States Patent 52,748
- United States Patent 82,629
- Internet Archive Wayback Machine. Web.archive.org. 2006-04-24. Retrieved 2012-11-01
- United States Patent 5,039,045