Lab Lessons—Wise Words From the Bench with Mukund Bhuta

By: Katie Anderson (Schaefer), Cosmetics & Toiletries magazine

Posted: June 30, 2011, from the July 2011 issue of Cosmetics & Toiletries.

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When testing aerosols, one must put the can in a hot water bath to increase the propellant vapor pressure of the finished product to determine whether the can is crimped properly, the valve system is not damaged during gassing, etc. As the propellant vapor pressure increases, the temperature inside the can increases. I once tried to pick up a can bare-handed and it blew up in my hand; I had to get 40 stitches. While the can was defective, I should have followed safety protocol and used tongs.

C&T: What else have you learned in terms of aerosol safety?

Liquefied petroleum gas propellants are flammable, so a test is used to determine how flammable they are and subsequently, which [caution] label to print on the can. If there is no flame, [no caution label is required] whereas flame size determines a “combustible”, “flammable” or “extremely flammable” label. I once was performing this test and forgot to put a mask on my face. It backfired and burned my eyebrows and hair.

C&T: What aerosol-specific regulation do you see broken most often?

The US Department of Transportation mandates that every aerosol can be passed through a water bath to achieve 130°F inside the can. If the crimp [sealing the can] is not closed properly or the can is defective, bubbles form in the water bath. The water used for this test then becomes waste water and must be destroyed with the proper waste management authorities rather than dumped into the sewer. Some companies bypass the water bath because it costs money to dispose of the waste water. Also, some use less water for the test, which is a problem because the can must be immersed. Finally, some companies do not use the right dwelling time; 2–2-½ min is necessary to achieve the right temperature.

C&T: What innovation do you see on the horizon for aerosol formulations?

Interest has grown in bag-on-valve systems due to VOC regulations. This innovation involves a bag made from four different layers of polyethylene terephthalate attached to a valve. A simple hair spray is placed in the bag while the propellant is placed around the bag in the can. This way, the propellant never contacts the hair spray and it is not sprayed from the product. The pressure increases outside of the bag, releasing the contained product.

C&T: Besides your consulting work, what are some of your hobbies?

I like reading about new aerosol developments and writing internationl safety procedures for aerosols. I also travel and give seminars about aerosol safety.

C&T: What do you find novel about aerosols?