April 2020

Aerosol Challenges: What keeps a good idea from becoming a marketable aerosol product?

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 the firm’s Marketing Director, who supported a new program, may retire or otherwise depart. 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 their 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 their 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 cosmetic ingredients list since they had never been used previously. Obtaining approval would require years of testing, so the project was abandoned.

An advertisement for The Hot One Self Heating Shave Cream from Gillette in the November 1970 edition of Hot Rod magazine. The problems of producing a self-heating shave cream ultimately outweighed the benefits.

























Over the years, a few aerosol products have entered the market only to be withdrawn when unanticipated problems became evident. About 1975, chemist Sam Prussen, consulting for Dart Industries, developed a self-heating aerosol shave cream and some other related products. The heat was generated when a 6% solution of hydrogen peroxide (H2O2) was mixed with sodium thiosulfate (Na2SO3). Working with a major valve company, Prussen devised a valve where the tailpiece dip-tube descended to the bottom of a 0.94″ OD (outside diameter) plastic inner container of H2O2, while a side dip-tube went into the shave cream and to the bottom of the aerosol can. The valve acted to proportionate the separate ingredients so that actuations would simultaneously empty both inner and outer products.

After royalty negotiations, a major aerosol filler produced about 25,000 units for the Rexall Drug Co. The filling process was extremely slow and costly, due to filling and attaching the H2O2 tube and hand inserting the valve assembly into the can. A slight excess of the shave cream phase was needed; a cool product at the end being preferable to spraying the 6% H2O2 solution. However, the most vexing problem was the generation of off-odor byproducts by the exothermic reaction, such as persulfate, dithionic and trithionic structures, producing the mild but unwanted odor of cooking eggs. Some other shave cream marketers launched products such as “The Hot One” and “Infernomatic Foam,” but the problems outweighed the benefits. The innovation disappeared within a year or two.

Despite thousands of hours of developmental work, the prediction that the food market has the greatest potential for aerosol product development still remains elusive. The U.S. food aerosol market of close to 500 million units is comprised almost entirely of two product types: whipped cream and cookware lubricant.

 Around 1970, the food market was touted as having the greatest potential for aerosol products. Despite thousands of hours of developmental work, that prediction still remains elusive. The U.S. food aerosol market of close to 500 million units is almost entirely due to only two product types: whipped creams and cookware lubricants. Some other countries, such as Brazil and Germany, have food aerosol markets so small that they go unreported in surveys. The greatest impediment is the possibility of microbial contamination.

Over the years, there have been several attempts to develop aerosol pancake batter. In perhaps the most sophisticated, a flowable batter was inoculated with sodium propionate, heated for 10 minutes at about 158°F (70°C), poured into pre-heated aerosol cans, sealed and gassed with about 2% carbon dioxide. Over 160 microorganisms were added, tested and failed to proliferate. However, the temperature was critical and every molecule of the batter had to be heated to that 158°F temperature, which posed a major challenge. Higher temperatures could not be used or the batter would begin to “cook” and thicken. Hundreds of filled cans were successfully stored at room temperatures for over one year. The batter became slightly less viscous, due to hormonal activity, but all other attributes (including appearance and taste) were perfectly normal.

When the product development program was detailed to several likely marketers it was rejected. The basis: if any bacteria or fungi escaped being killed by the processing program, the marketer could face thousands of lawsuits based on distributing an unsafe food product. Alternatives such as sterilizing by atomic radiation were considered but also rejected.

Eventually, some aerosol pancake batter products were launched—such as Batter Blaster and Nate’s Homemade Pancake & Waffle Batter—but they are no longer available for purchase.

About 1975, at the suggestion of a marketer, a major filler developed an aerosol emulsion to ignite beds of charcoal briquettes in outdoor grills. The formula consisted of about 86% odorless mineral spirits (OMS), 4% water, 2% surfactants, 1% minor ingredients and 7% propane. The foam could be spiraled onto the charcoal and lit by touching a match to it. The foam could then “melt” into the charcoal, igniting it. After a small test market, the marketer approved the product, but with the proviso that the foam was to be colored yellow. Wisely, the filler obtained a Hold Harmless Agreement (a legal agreement that states that one party will not hold another party liable for risk—often physical risk or damage), then added an FD&C Yellow colorant to the formula.























The product looked normal after about six weeks, when commercial production began. However, after many months the colorant dissolved enough divalent and tetravalent tin from the lead-free side seam that the emulsion collapsed, freeing the OMS/propane as a separate top layer. Some unusual consumer experiences followed. No one was harmed but the remaining product was withdrawn. In later years, a gel type charcoal lighter was developed, but did not do well.

They work, but…

Some aerosols were perfectly developed for their intended purpose but failed to meet marketing requirements. About 1980, an east coast aerosol laboratory developed a “Permanent Starch Spray.” It was based on about 2.5% of a colorless, water-resistant copolymer, dispersed in a suitable emulsion system. While not exactly “permanent,” it was said to survive from about 5–8 shirt washings, depending on conditions. When the product was shown to aero-starch manufacturers by marketers, it was rejected for two main reasons. Consumers could not know if a particular shirt or blouse had been sprayed one wash cycle ago (thus not needing a re-spray) or many cycles ago (thus needing a re-spray). However, the larger problem was that the synthetic product could replace several cans of natural starch, therefore greatly diminishing the existing aero-starch market.

A well-known South American formulator created a phosphorescent “Calglow” product, similar to the appearance of fireflies. Two fluids had to be mixed in the aerosol valve. A newspaper sprayed with the product could then be read in a completely dark room. It did not succeed. In the U.S., however, two similar, albeit very niche, products are available in the form of Glow Spray from Photonix and Rust-Oleum Glow in the Dark spray paint.

Another major marketer developed a series of “cola type” beverage concentrates. A large aerosol can would hold enough product to produce 24 eight-ounce (236mL) drinks when added to water and cracked ice. The carbon dioxide propellant directed a forceful stream of 16–20mL of product into the water, making stirring unnecessary. The product was marketed and almost immediately produced a plethora of consumer complaints. People could not judge how much concentrate to add. However, the greatest problem was when the highly colored streak of concentrate careened off floating ice cubes, bouncing onto shirts, dresses, napkins, tablecloths and other surfaces. The products were quickly withdrawn.

In Japan and China, consumers can purchase aerosols with 85% to 99% oxygen gas. They can be used—among other reasons—to energize tired shoppers, temporarily relieve bronchitis or help prevent older people from fainting when traveling from China to Tibet or Nepal, where roads can exceed 18,000 feet in altitude. The cans are sometimes returnable to the retailer, especially if the store has a large oxygen cylinder and pressure regulating equipment. Most stores will charge for the oxygen, even if the dispenser was never used. They claim the gas is so lightweight that the cans appear to be empty, whether they have been used or not. There have been periodic attempts to introduce oxy-aerosols into U.S. markets, but there have been U.S. Dept. of Transportation (DOT)-based regulatory concerns, and more importantly, no one seems to want them.

Trekkers in Tibet can purchase oxygen in a can.
Photo: National Geographic















Finally, a somewhat similar situation exists when nitrogen-propelled aerosols are used to dispense honey, syrups and other “low water activity” food products. The viscous liquid looks perfectly normal for the first few seconds, but the turns opaque and white as millions of nitrogen gas bubbles materialize. After a few minutes the bubbles further coalesce, rise to the liquid surface and disappear, leaving the product clear and normal. However, most consumers are concerned (even frightened) by these mysterious changes, often thinking they may indicate microbial spoilage events. A few specialty marketers offer these products, but the sales volume is small.

 Never discouraged

Aerosol product development laboratories are continuing to work on novel products, as well as modifying existing mainstream ones, creating flankers, making adjustments to cope with regulatory and environmental concerns, and so forth. Being aware of the many pitfalls will improve the possibility for commercial success.   SPRAY