Adorable Aerosols Part 2 - Packaging

May

Adorable Aerosols Part 2 - Packaging

As we discussed in Part 1 of this series, aerosols are a popular delivery system used in all kinds of household and beauty care products from Air fresheners to Zit creams. But did you realize that aerosols are different from ALL other beauty products because the package itself actually determines the product’s physical properties? In this second part of the Adorable Aerosols series we explain the mechanics of aerosol packaging: the can that holds the product and the valve that controls how the product is dispensed.

Aerosol Cans

If you think about it, an aerosol product is kind of like a bomb. That’s because it contains a pressurized, and potentially flammable, gas. So it`s important that the container is strong enough to withstand increases in pressure. Otherwise the hairspray you left in the back of your car in the middle of August would go Ka-boom! No worries though, because steel and aluminum are used to make aerosols cans extra sturdy. Let’s take a look at each type.

Steel cans are easily recognized because they’re assembled from 3 separate pieces. The body of the can is formed by rolling a sheet of metal into a cylinder. The top and bottom (known as the crown and the base) are formed from separate pieces. All three of these pieces are crimped together to form the can. If you can see the seam down the side of the can and the rim where the top and bottom pieces are attached, you know it’s a steel can.

Aluminum cans, on the other hand, look smooth and sleek because they’re formed by extruding a single slug of aluminum into the desired shape. Both cans are designed with a domed top and inverted bottom to help them invert or bulge if the pressure in the can increases. This allows the can to distort and increase in volume, so it can relieve pressure without bursting.

Steel cans are more commonly used because they’re stronger, cheaper, and easier to process. But aluminum cans are more elegant looking and they are less reactive to water-based products. And both can types are designed for recycling when empty.
Depending on the brand you buy, you can find products in either type of can. Regardless of the whether it`s made from steel or aluminum, the can is sealed with a piece of hardware called a valve.

Valves

Aerosol valves have to do double duty: they have to seal the opening of the can so it doesn’t leak and they have to control how the product is dispensed. The way they accomplish these tasks is really a miracle of modern engineering.

Valves have three main sections: the part you are most familiar with is the button, or actuator that sits on top of the can. This is the part of the valve you push on to release the product. The button has a small opening though which the product comes out. In the case of a spray product, this orifice is very small and the product comes out as a very fine mist. In the case of a mousse or shaving cream, the orifice is a larger spout and the product comes out as a thick foam.

In either case, when you push the button it compresses a spring that opens up a small channel inside the body of the valve. Inside the valve body there are a series of small chambers where the product can mix with the propellant.

The bottom of the valve body is attached to a long, thin straw-like piece of plastic known as a diptube. The diptube extends to the bottom of the container and carries the product from the bottom up to the valve. (have you ever wondered why you have to turn some products upside down to get them to spray properly? That’s because they don’t have a diptube! You have to invert the package so the product inside can reach the valve body.)

All these tiny parts are collected in a steel or aluminum housing, known as the valve cup, that is crimped over the opening of the can after it is filled with the formula and the propellant.

So, when it all comes together, the valve works like this: When the button is pushed, the gas inside the can pushes the formula up through the diptube into the valve body where it is broken up into tiny particles and finally forced out of the small opening on the face of the button. In other words, “Push button, stuff comes out.” Seems simple, but it’s really pretty amazing, huh?

The really astounding part is that these components have measured to a 1/1,000 of an inch or they won`t fit together and the valve won’t function properly. Think about that the next time you’re spritzing your hair.

Ok, now that you’re properly in awe of the miracle of aerosol packaging, you’re ready for a chemistry lesson on what’s inside. Come back to the Beauty Brains for Part 3 of Adorable Aerosols and we’ll tell you about the formulas and propellants used in cosmetic products.