Science and Pumps

[The Ranger]

One of my 2nd graders was mesmerized by the foaming action of the newest soap dispenser from Johnson&Johnson; press the pump and foam surges out the spout and into your hand. I *thought* I could explain it quickly but even after we tore the spout apart, it defied our attempts.

Would there be someone here that understands how the soap is processed into foam without water being added and rubbing your hands together? Diagrams that I might blow up and use to explain the process are _always_ appreciated!

The Ranger

[Dean Hoffman]

The answer might be here:

[Frank]

You need gas for foam. It is either generated chemically, dissolved under pressure or added when dispensing. I would guess one of the latter two.

[The Ranger]

Alas, my previous searches of that site, and Answer.com netted me a goose egg. Clearing out the cookies and such returned many more unrelated articles on the how's-and-why's.

The Ranger

[JIMMIE]

Just like soda pop in a bottle.

Jimmie

[David Nebenzahl]

On 2/14/2010 11:40 AM Frank spake thus:

Put more simply, the dispenser mixes air with the liquid soap to make foam. (How exactly that works inside the pump I don't know. I'd be curious to see a diagram if someone can come up with one.)

[hrhofmann]

Find a phone number on a JNJ product and call them on Monday.

[David Nebenzahl]

On 2/14/2010 12:59 PM hr(bob) [e-mail] spake thus:

By JNJ I take it you mean Johnson & Johnson? I seriously doubt they'd be much help; after all, they don't manufacture the pumps. They just package the stuff and sell it.

[trader4]

I've seen dishwashing soap pump dispensers now that produce instant foam. They work really well. I think Palmolive makes them. Only problem is they cost so much more it's just not worth it. I would guess they produce the foam by combining atmospheric air with the liquid. It is definitely a different type of soap, you can't use regular dishwashing liquid in them.

[E Z Peaces]

In the 1950s, the a loose-fitting piston was used. On one stroke, air and soap would be sucked in past the piston. On the other stroke, the piston would eject the resulting foam.

Later designs used a diaphragm to create pressure. In a newer design, squeezing a bottle pumps air and soap into a chamber above. The air enters at the bottom of the chamber, where it bubbles up, creating foam on top of the liquid soap.

[hrhofmann]

The OP was looking for something he could show his students. Any ideas for a web site where he could get this information?

[The Daring Dufas]

Did you ever think of contacting the manufacturer? If you were to explain that your inquiry was to educate young students in the mysteries of science, I'm sure someone at Johnson & Johnson would bend over backwards to help you. I'll bet one of the scientists would put something together for the kids.

TDD

[tnom]

My guess would be the venturi effect.

Basically the diameter of the tube that transports the soap becomes much smaller. This creates a faster moving fluid within this smaller section. If a tiny hole was introduced into the side of this small diameter section it would see a vacuum. Hook air to this tiny hole and you have a foam machine also called a venturi injector.

[aemeijers]

My brother's old rental house had a shower head like that. Looked like just a squished piece of pipe, and first time guests would usually stick their head out the bathroom door, and ask where the shower head was. Worked great, though. Wish I could find a place to buy one.

-- aem sends...

[tnom]

[The Daring Dufas]

I have a couple of cleaning foam sprayers used for cleaning HVAC and refrigeration coils. The sprayers hook to a water hose and turn the detergent in the reservoir into foam when mixed with air and water when is sprays out of the venturi/aerator attachment. Here is a link to a picture of one and the black tip sticking out of the sprayer has air holes and a venturi. If you look closely, you can see it.

A fellow who owns an air conditioner repair service might let a teacher borrow one to show the kids in the class how something like it works. If I lived close enough, I'd let a teacher borrow one. Heck, the school maintenance department may have one!

TDD

[Hustlin' Hank]

To understand it, look up "eductor" or "venturi" action. As air is forced thru the tube, a vacuum is created which pulls the liquid (soap) thru a venturi (small orifice) that mixes together with the air. This is also the way a carbeurator works on a car.

Hank

[Caesar Romano]

On Mon, 15 Feb 2010 18:50:12 -0500, [e-mail] wrote Re Re: Science and Pumps:

Nice site. Thanks

[hrhofmann]

JNJ is their stock ticker ID. It couldn't have hurt to try.

[E Z Peaces]

That would produce a mist of air with soap droplets. A liquid run through a venturi could draw in bubbles of air, but soap seems too viscous for that.

I wonder if there is a patent number on the container. S C Johnson has patented foaming dispensers. I wonder if there's a specific list of ingredients. S C Johnson has patented formulas for post-foaming shaving gels.