Montfort A. Johnsen
For every aerosol product enjoying commercial popularity, there are several that never quite
got there—or if they did, their success was ephemeral, flickering out for one reason or another.
These disasters, large and small, had many attributes. Unexpected corrosion certainly
took its toll. Others succumbed from color or odor changes, patent infringements, regulatory
limits or simply because consumers were not interested in buying them.
These days, product formulators have a difficult challenge in keeping up with all the elements that
must be tested or otherwise considered. Over 500,000 ingredients are available, as well as hundreds
of can and valve choices. Any significant selection error could set a development program back many
months or even cast it into limbo. Aside from the technical area, other negative events may occur.
In some cases a firm’s Marketing Director, who supported a new program, retired or otherwise departed.
His or her replacement may have other priorities, causing the program to be disenfranchised.
Fortunately, in almost every case, defective aerosol products are detected during the development
stages. Events where they enter the marketplace are incredibly rare and most marketers have “Product
Recall” manuals for guidance should this happen. However, nearly all defective prototypes just sit
on shelves for decades, without ever being utilized.
Summarizing some of the industry’s experiences with product development “disconnects” may be
useful toward preventing such occurrences in the future.
Formulation Disparities
Probably the earliest can corrosion event was in 1953, when the manager of a product distribution
warehouse notified a marketer that his new pyrethrum-DDT-based insecticide was staining some
cartons and leaking product on the concrete floor. It was soon determined that the development
group has used a chemically pure (bone dry) grade of dichlorodiphenyltrichloroethane (DDT) in its
formulation work, but the purchasing department ordered a less costly commercial grade product
that typically contained about 0.3% moisture. The free water slowly hydrolyzed the CFC-11 (trichlorofluoromethane)
propellant component, forming tiny amounts of hydrochloric acid—enough
to perforate the tinplate cans. In the aftermath, the two tinplate can companies involved began the
development of organically lined cans and the supplier found that 0.5% of nitromethane would
make CFC-11 resistant to hydrolysis by water. It was then called CFC-11-S.
About 1951, Carter-Wallace developed and patented shave cream foams, using about 9% of
chlorofluorocarbon (CFC) propellants. A major competitor felt the patent was invalid and began
producing comparable aerosol products. A lawsuit and litigation followed in 1953, ending by a judgment
upholding the patent. Carter-Wallace was awarded about $3 million, but shortly learned that
its competitor had developed excellent shaving cream foams using about 4% low-cost and low-odor
hydrocarbon propellants. The formulas were clearly outside the scope of the patent. They marked
the first use of hydrocarbon aerosol propellants, which are so popular today.
Phenolphthalien and thymolphthalien are well-known colorametric pH value indicators sometimes
used in chemical titrations. Phenolphthalien changes from the leuco form (colorless) to
reddish pink in water-based solutions if the pH is above about 7.8. Similarly, thymolphthalien turns
bright blue at pH values above about 8.1. It was found that indicator colored aerosol shampoo foams
changed to the leuco form when massaged onto the hair and scalp. This is because the stratum
corneum outer layer of skin contains lactic acid, urocanic acid, free fatty acids and others, creating a
pH gradient that ranges from about 4.3 to 5.8, averaging about 5.4 at 25°C (77°F).
When the colored shampoo solubilizes, these acids in the foam turn white. The development
group felt this “magical” transition could be commercially important. Sales personnel concurred
and the names “PinkyPoo” and “BluPoo” were considered. Fortunately, near the beginning of the
marketing program, the legal department reviewed the dossier and pointed out that the two coloring
agents were not grandfathered into the U.S. Food & Drug Administration (FDA)’s approved
Technical Editor
Aerosol
Challenges
What keeps a good idea from becoming
a marketable aerosol product?
30 Spray March 2020